I had an idea to mention any poor designs here. These relate to sets or other items where you either say, "No I don't do those..take it away!" or you feel sorry for the owner and grudgingly take it off their hands and later regret ever having started, or some that you start full of confidence that later make you REALLY annoyed!
I have a few cardboard boxes around the workshop with unfinished examples of some of the latter
Sometimes I actually complete one of these jobs and it's successful.
Some of them are listed below with the most recent added to the top so the numberings upside down!
I've also included more than a few things that really annoy me and in most cases there's no-one to complain to!
One can't blame the batteries. There is a little known law of nature which is pretty elementary when you think about it. This is the "Theory" or "Principle of Entropy". Nature is basically in equilibrium or at least is trying its darndest to get that way. Man is working against nature in a simplistic way of putting it. If you think of anything that man does to produce order, or to make something contrary to that found in nature it can be expressed as giving the object an Entropic value. The more effort that goes into something, generally speaking, the higher the entropy. Nature on the other hand is striving to produce a state of equilibrium and this can be expressed, as far as Nature is concerned, as reducing the entropy of an object.
Take a steel fitting. Iron ore is smelted, various other minerals are processed and added to the mix, a billet is produced, heated and rolled, cut into pieces and machined. Each process adds to the entropy. Place the steel fitting somewhere "visible" to the forces of nature and what do you get?
After a wait depending on how hard nature tries, you get something pretty close to iron ore. The entropy has been reduced to a minimum which is the way nature likes things. Virtually anything you can imagine goes that way given time, maybe with the exception of the odd plastic bag. If you paint something, which is essentially adding a goodly amount of entropy, Nature will work on the paint and cause it to peel off and then get down to the business of reducing whatever you protected to its basic state ... dust.
An old lady sent me her teasmade which had stopped working. 30 years ago we had a teasmade and it was very reliable. The trouble was, my wife wasn't and she set it up one night without the teapot. Next morning the boiling water gushed out all over the bedside table and removed the varnish. We stopped using it eventually because the water in Cheltenham, where we lived, ate through the element and I couldn't be bothered fixing it. I do remember though that it was made of some wire, some switches, a buzzer and a 50Hz synchronous clock which worked off the mains and a little neon lamp. It ran for donkeys years and was pretty reliable. The clock, near end of life, sounded like a motor bike and I had it hooked up to a radio as well as its internal buzzer. When I looked at the 2000 teasmade it had a fairly large printed circuit board with loads of discrete components including resistors, capacitors, diodes, transistors, an integrated circuit, a relay, and an electronic buzzer. The clock consisted of another printed circuit board with many components including a quartz crystal etc. The teasmaid STILL had a couple of switches, the kettle with its heating element, a small neon and some wires. How can the new design be justified? It performs exactly the same function as the 1967 version. It's clock is smaller. It uses maybe thirty times as many components including complex integrated circuits. It consumes more power AND it is UNRELIABLE. The reason for the failure of the new teasmade? The power supply to the complicated circuitry has failed. A 24 volt zener diode was short-circuit. The old teasmade didn't have a power supply let alone a zener diode! The new teasmade cost over £50. Why? Because of the cost of all the components, the design of the thing and its assembly.
Take the repair costs. To change the zener diode one must remove the top cover, the kettle gasket, the bottom cover, the front plastic cover, the four hands from the clock, the plastic decorative panels, the clock module, the printed circuit board and finally its protective plastic cover. One cannot immediately identify a faulty component as various component checks must first be made to establish which has failed. Finally having found the faulty part, in this case the zener diode, it has to be unsoldered and a new one fitted. Then the teasmade has to be reassembled and tested.
I didn't mention the problems met in disassembly. For some reason the front plastic cover, which must remain undamaged for "cosmetic" reasons is secured by barbs which are almost impossible to detach. A wrong move and the plastic front is damaged and the thing will look awful. In fact the cover is so difficult to remove one may be excused for thinking, that once fitted, it was never intended to be removed.
All in all, the failure of a twopenny zener diode could have resulted in the teasmaid becoming mere scrap. Who else other than repairers like myself, prepared to work for a pittance, would undertake such a job?
PS. A lady came to the door the other day carrying THREE more teasmades...groan! It turned out that every couple of years when the current model stopped working it was consigned to the garage and a new one was purchased. As the owner is 90, I wonder whether the quantity delivered was governed by their weight or when the garage was last cleared out? If the former I can imagine there's another couple of dozen still in the pipeline!!
Since I wrote the above I found out what was wrong with the other ones! For a start they didn't have the circuit board with the unreliable silicon bits. It seems that the old ladies water supply is fairly hard and deposits had accumulated inside the spouts. When I tested the first of the three instead of boiling water going into the teapot steam came out of the vent hole in the top of the kettle and from around the lid seal. At first I thought it was a missing safety valve in the lid but when I investigated further I found the spout was completely blocked with calcium sulphate (I think?). Because of the tight bend in the tube deposits had formed over the two years the thing had lasted. The day after each had made its last cup of tea the safety valve must have been ejected and duly hoovered up by the home help who delivered the errant devices to my door. Presumably all the examples collected in her garage were the same! A poke with a bent wire sorted out the blockages. Presumably the problem is well known in the annals of teasmade repairers!
Last week a humidifier arrived in the workshop from a customer in the same area. The scale deposits from the hard water in Burley had grown over the heater element pushing aside the rubber seal allowing water to penetrate the top in which resides live mains wiring. As the equipment is less than two years old and hasn't seen much use I can only imagine the vast number of other things affected similarly in Burley. I suppose if one wanted to make a lot of money one could open a shop there selling those sort of things... electric kettles, immersion heaters, teasmades etc....
I have quite a lot to say on the subject of digital TV. We recently got a FREE SKY DIGIBOX. I installed it myself so it really was free. I received a FREE SKY card and we watch the FREE channels.
I used to complain that when a 16:9 program came on terrestrial TV you only saw half a picture. Why should one pay 100% TV license when you only get half a picture! The TV may be capable of 625 lines but half a picture is only 312.5 lines so overall quality must only be 50% of what's possible.
On Sky Digital the situation is different. Most programs are transmitted in 16:9 format and on an ordinary TV you set up the menu to receive a full picture top to bottom. Unfortunately, again you only see half a picture. The left and right sides are missing. This is particularly noticeable when captions are shown and you only see the middle bits. Why should we pay 100% of our TV license and see only half a picture? If you set up the menu to show 16:9 you get the same results as terrestrial TV (half a picture).
In summary, if you have a 4:3 TV you should only pay 50% of your TV license because no matter what you do you only see half a picture!
Digital picture quality is OK but has only the same quality as a good VCR picture. If you saw a good terrestrial picture side by side with a digital picture you would certainly see the difference. Basically terrestrial TV has a video bandwidth of about 5MHz or so, digital TV has a bandwidth, like VCRs of about 3MHz. The monitor on which I am typing this has a bandwidth of about 140MHz. Bandwidth equates to picture clarity. Unfortunately digital processing technology hasn't quite caught up with politician's aspirations. Every few minutes when viewing a digital picture it kind of stutters. After a while I try to predict when it'll happen. Steady movement especially in conjunction with diagonal sort of picture content is a problem. I wonder whether this problem will ever be sorted out or is it going to be with us for ever.
The trouble is: lots of money can be made by using digital TV. Government can sell off spectrum and can get a lot more for what is used. The TV people can pump out more programs in a given amount of spectrum space. More programs equals more advertising equals more money. As far as the BBC is concerned. They are transmitting more channels and they will obviously need more people to handle the extra work and more money from us for their license fee. In summary we'll get more than we need, pay more than we should, and worst of all: what we get will be of inferior quality. The regulations concerning all this are not worth the paper, I bet you haven't even seen, that they're printed on!
Have you ever thought through what will happen in a few years? The old analogue TV stations will be switched off. You will have a set top box or a digital TV. You will need a card which must be inserted before you can view anything. You can distribute TV around the house BUT you can only watch one channel at a time unless you have a viewing card and another set top box. The first box may have been free but the price of a second box is £400. You will need a second dish but regulations say you can have only one! You can buy a bigger dish and fit two LNB's. This can be a very costly business! VCRs will need their own set top box otherwise you can only record what the TV is tuned to. If you're watching it already why record it? Basically you can chuck away your portable TV sets and your VCRs because you won't be able to use them after analogue is turned off in a few years.
If your analogue TV picture is not absolutely perfect you will not be able to receive digital terrestrial TV. If you have a lot of trees or obstructions to the south you may not be able to receive digital satellite TV. If you live in a country area you won't get digital cable. You can listen to the radio though. Or can you? Are there not plans to cease transmission of AM and FM and go digital? Why bother at all, the Victorians didn't have radio or TV!
I started watching a thing called Einstein TV the other night. I packed it in because every minute or so the sound would cut out and the announcer's expression would freeze for a second or two. It's all very well when you get a little noise on the picture, it isn't really noticeable, but digital can't stand a noisy signal. At the drop of a hat the picture will freeze until the signal improves. If it doesn't improve in a moment or so you'll get a message such as "Technical Difficulties" or "No Signal". This will happen in heavy rain or if branches from a tree waft in front of the dish when it's windy.
Good news for non-digital TV viewers. Since a member of the Government tried to buy a "Free-to Air" digital TV (as opposed to one for which you need a subscription to watch) and found he couldn't... it looks like analogue switch off may be delayed. This is re-inforced by a recent survey which found that more viewers than the government had allowed for in their formula that would not be equipped to receive the new transmissions (to meet the switch off requirement) said they wouldn't switch to digital! Clearly some redefinition of the parameters is required! You mark my words some new weazel words will be found! Another possibility is to provide FREE set top boxes for the "stick in the mud" viewers. Unfortunately things are not that easy as in addition to the extra box one will need a re-vamped aerial system in many cases as well. The cost of the latter has been quoted by some as around £250. Boxes are currently £400 to buy outright.
By the way. Did you ever wonder why ITV is not available on Sky? Well I understand Sky wanted £20 million a year for the exercise. However it is understood that ITV are negotiating a deal with SES the satellite owners, instead of Sky (there is a difference!), to put themselves on satellite in parallel with the Sky channels. Of course this will cost a lot less £100 million for 10 years! I'm sure we haven't heard the last of this yet.
Have you noticed that BBC standards are slipping? One cannot now always tell that it's the BBC you're watching. BBC used to have standards that other broadcasters, the world over, often saw as an impossible-to-meet yardstick of excellence. Now bad language and poor taste are commonplace.
Do you know that before 1939 BBC announcers were anonymous? The Government had an idea before war got under way that if BBC announcers had well known voices and could be identified by the public then the enemy wouldn't be able to broadcast propaganda in the guise of the BBC. The idea had supporters but also detractors. A chap that wrote for Practical Wireless was horrified that mere announcers could become famous in their own right. He reckoned that the job would get over-rated and after all they didn't need a brain or ability just an Oxford accent and a list of BBC pronunciations. Was he right?
Enjoyment of games such as rugby or cricket is being ruined by ugly and intrusive advertising. When half the screen's taken up with a huge, painted grass advert, I'd rather BBC did a deal and put an advert on every half hour in exchange for leaving the grass its natural colour! Ask whoever thought up the idea, "Why not cover ALL the grass with adverts. Don't bother to let any green show through because it's lost revenue". They'd probably say, "No it would detract from the enjoyment of the game". "Alright lets have adverts painted over just the left half of the pitch". "That would still detract from the enjoyment of the game". "What about a quarter of the pitch....." etc. Presumably the amount that's painted over is carefully calculated so that the number of complaints is kept down to 29.5 or some such figure determined by an overpaid pen-pusher at the BBC, the FA or somewhere?
The latest fad is using multiple continuous TV screens all around the football pitch perimeter for advertising! My enjoyment, watching the Albania-England match the other night, was marred by an incessant brightly coloured band of adverts clearly trying to catch the viewer's eye. The things were cavorting round.. left.. right... rolling and dancing up and down. It made me dizzy and I kept missing bits. The fact that it was digital made matters worse, making the movement jumpy rather than smooth which added to the distraction. The worst offender was Channel 5's own rainbow coloured advert! Whoever thought this one up obviously doesn't watch football on TV. They were even advertising their next program! so clearly it isn't aimed at the fans who paid their money to go to the ground.
Gone are the days when watching an English Football team playing in Europe was an extension of watching the English Team. How can one support a team when maybe only one player is British? It used to be that our team had the "clean" players and it was only the foreign teams that were up to no good and did nasty things like professional fouls. Now it's different because nearly all the players in a European match are foreigners and most would not understand the term "not cricket!". Soon the English Manager (Ha! Ha!) will have to look to the lower divisions and even minor leagues for his players as there won't be anyone in the Premier and First division that's eligible to play! Everything seems to hinge around MONEY now.... We get our gas from an electric company, electricity from the gas board and I see now the gas people are now into telephones! It used to cost less than 1p to post a letter and there were three deliveries a day. Now it's nearly thirty times that to post a letter and there's only one delivery a day!
I needed to talk to BT the other night so I rang "150". The line rang then a recorded voice said I had to press "star" on my telephone. Then I had to listen to some instructions. None of the options was quite right but one added that "anything else" was thrown in, so I pressed "3". The line rang for 25 seconds before there was a loud click and an extremely loud voice came on to say that all the people were busy but if I waited I would be put through in a jiffy (or somesuch words). I waited and the line rang again until 25 seconds later the same extremely loud voice came on and said the same thing. I waited patiently for over 20 minutes during which time the EXTREMELY LOUD voice came on 40 times. When I had almost decided to cut my losses and give in, a quiet Scottish voice came on the line and asked if he could help (do you know that Scottish people are used because it's hard to get angry with someone speaking in a nice Scottish brogue?) I said I'd been waiting over 20 minutes and I was now deaf in one ear because of the VERY LOUD voice that kept coming on the line assuring me my wait was for only a trice. He read from a card something which pacified me for the moment and I asked my question. He didn't know the answer but he'd find out. He said he wouldn't switch on the music as, he said, "people don't like it" and the line went quiet. He came back with an answer. My second question had the same result. My third question resulted in "mostly it's OK but you'll have to pay for it first". If it didn't work they would cancel the order. I realised I needn't have bothered asking any questions as he didn't really know the answer.
Now came the interesting bit.... he voluteered...."I'm sorry you had to wait, but there's only two of us. I'm McTavish (name changed) and Cyril (name changed) is in Newcastle". "What!" I said, "for a country of 60 million people (sorry, I was guessing) there's only two operators for all BT enquiries? "Yes", he said, "after 11pm there's only two of us but if you wait till after 2am it gets a bit quieter and you shouldn't have to wait too long". The call had taken 15 minutes from when he'd answered. I wondered how many people were also deaf in their right ear.
Those involved in the TV trade or the repair trade generally may have noticed over the years that parts have been getting smaller. This applies to resistors, capacitors, mains transformers (say in microwave ovens) and particularly transistors. Why is it that some TV receivers have a small BUT11 style device with no heatsink as a line output transistor and others have a huge chunky device with a substantial heatsink? May be it has something to do with tolerancing of components resulting in a wide variation of performance? One specific item however has been annoying me lately and that is the line output transformer. Not that the physical size has changed because that seems to be fixed; maybe it's something to do with the spacing necessary to provide high voltage isolation? What is happening is more frequent failures of almost new transformers. Not just originals but also pattern types marked with the "HR" codes (perhaps they are the same?). Are margins being increased by changing to different materials, or maybe less of them? Are workers getting less meticulous in their day to day jobs? Or has post-production testing been totally given up leaving this to the setmakers or repairers?
One problem seems to be lack of adequate insulation resulting in a discharge through the plastic covering to either the core material or adjacent components on the circuit board.
One Bush TV recently led me to tear my hair. It was a nearly new set and the fault was a burnt out diode situated next to the LOPT. I replaced it, wondering why it had failed, and tested the set with its back off. After a few minutes there was the sound of lightning coming from inside the set. A large spark was jumping between the lower part of the LOPT plastic case and the new diode.
I checked with CPC and discovered a replacement (genuine) LOPT at a sensible price. It was a special order. I waited till after Christmas because trade was low and I didn't have the minimum free postage order value. A few days into January I ordered it and it arrived through the letter box in a jiffy bag a few weeks later. Normally LOPTs come in a box protected with shaped polystyrene packing materials.This didn't (more cost cutting!) and of course the core was broken. I complained to CPC and asked them to see if they could get the replacement better wrapped. It arrived a few weeks later, thankfully intact although still loose in a jiffy bag!
The set is now working again and the customer has collected it after waiting the best part of 3 months. I wonder if the new LOPT will last any longer than the original? To whom do we apply the necessary feedback to try and improve quality?
I had a nearly new set in the other day. The mains switch had failed. These can be nasty as a fire can result if not sorted out. This one was making a fizzing crackling noise and is almost certainly a result of using a switch too small for the job. Not only is it too small its not a standard type but a special order. To save a couple of pence on production costs some manufacturers are now using parts which are clearly not up to the job and to cover myself I've got to fit an exact replacement.
I recently had in a Panasonic digital mixer that had gone u/s. The device cost hundreds of pounds and came with a huge handbook that made the thing look extremely important. A brief scan through the book revealed it was printed in a host of languages and the English bit although not thin was certainly not as important as the outside cover had promised. This seems to be the rule nowadays. One settles down for a good read to find that there's really only 2 pages with information and 102 pages of foreign stuff, introductions, how it conforms to PTT regulations for using it in New Zealand etc.
Interestingly what did catch my eye was a sentence that said the handbook didn't give every detail about the device. It could do a lot more than was described. Presumably one has to fiddle with it to see what the dozens of sliders, knobs and push buttons do? The legends printed above them seem to me to be totally meaningless but perhaps if you use a digital mixer you're supposed to understand what everything's for?
Anyway back to the non-mixing mixer. Not a very auspicious start as I had to use the handbook to find the on/off switch which was hidden away on the side of the case.
There was no video output which was a shame as that's the key thing about a video mixer. With no output the best one could do with it is to use it as a paperweight.
I opened it up and found an enormous array of microprocessors, three huge square chips with hundreds of pins, surrounded by dozens of surface mounting chips with loads of legs so tiny they merged into a single grey blur. I detached the main circuit board and having turned it over and removed a large aluminium screen, I could see loads more surface mounted chips and a sea of resistors, capacitors, diodes and transistors. Everything was surface mounted and everything seemed to be 50% smaller than I'd seen before.
My 1.5" eyeglass was just adequate to see a small resistor in series with the video output, connecting a microscopic gold through plated hole to a microscopically thin gold track to the output phono socket. My meter probes, although having sharpened ends looked like pokers when I placed them either side of the tiny resistor. It read 34Mohms. I couldn't believe my luck! To confirm it I checked its mate which connected to the "monitor" output. It read 75ohms. What a relief! I unsoldered the duff resistor with my needle pointed soldering iron and fitted a new one. The fine tweezers almost completely covered the resistor chip but it finally lay there stuck in place. I measured it and saw a reading half a million times less than the original. After re-assembling it all with its host of flexi-cables and metal screening plates I plugged in the signal generator and the TV to be rewarded with colour bars.
Why had the resistor failed? It probably only had a few tens of milliwatts of dissipation capability so I imagine the owner must have connected the output phono to something carrying a DC voltage or a hefty AC signal. As all the connections are made via phono plugs, and there were something like 17 of them if my memory serves me well, it would be easy to switch a few round in error, connecting a signal destined for input to a socket carrying an output. Was the customer to blame or is the mixer really unfit for purpose?
I sometimes get in a set that has been watered. On top is kept a pot plant and this sometimes overflows into its saucer which then leaks over the top of the set and down the back, through the vents and onto the circuit board. Usually there's a bang and the set goes off. These are easy to fix, being usually a fuse or a power transistor. If I get one and fix it easily I charge a nominal amount but if it comes in again with the same complaint I double the bill. I haven't seen the same one three times yet. The other day I received a set that had been liberally watered over a low voltage section of its circuit board around the tuner. It could have been rain water travelling down the outside of aerial coax in this case, and thence through holes in the rear of the case near to the tuner.
As the circuitry was low voltage and the set had presumably been on standby the resulting damage was limited to electrolytic corrosion. That is, various components joined by water had acted like little chemical cells ("batteries" to the layman). Metal had been transferred from one component to another (forming the negative electrode of the cell). Tinned jumper wires were now missing their tin plating, and lots of other components were in various states of disrepair. A small electrolytic capacitor was now legless, the tuner unit was missing a pin which had dissolved and there were areas of green gunge dotted around. The set worked fine, insofar that it was producing a bright noise-filled raster but it wouldn't receive any stations. The missing tuner pin was the one carrying the tuning voltage. Being around 30 volts this had presumably been worst hit or had produced more bubbles than the lower voltages.
I had to remove all the components affected as there was a lot of corrosive by-products trapped underneath them. Some components were inside a heavy metal screen soldered to the main circuit board and this took some shifting. After removing then cleaning the legs of a 62 pin microprocessor, dismantling the tuner unit (a lot of unsoldering involved), cleaning it and fitting a new leg, fitting a new capacitor, and cleaning away a dozen areas of green gunge, I washed the area with iso-propyl alcohol, reassembled everything and was rewarded after re-tuning with the local stations.
Lets hope the customer's aerial lead is repositioned so that rain drips off outside the house instead of inside the set! I did explain and this turned out to be the likely explanation. I understand that early TV feeder in the US was balanced and was in the shape of a hollow tube. It was a frequent occurrence for rain to travel down the inside of this stuff straight into a TV, with little external evidence, except perhaps a watery picture and gurgling sound, until a loud bang and a flash when the water level had risen to cover mains circuitry.
|One report I read on this set says you have to be psychic to mend their faults. The thing is protected up to the hilt with circuitry designed to prevent the set blowing up if there's a nasty fault. Unfortunately the circuitry is less reliable than the things it monitors. Most of the parts are either microprocessor chips or surface mounted components, not easily changed. As the set normally takes about 20 seconds to come on (when there's no faults) it's a bit of an anti-climax turning on a faulty set. One waits 30 seconds and starts to think there's something wrong. After a minute and there's still no picture you're sure there is. Unfortunately when I started making measurements around the processor the set came on. Now it works all day quite normally. You can't fail it, that is until the next day when it's turned on and after 30 seconds there's no picture! I thought of extending Pin22 to a push button. "Press this when you want the set to come on and press it again to make it go off". It'll work fine but I'd rather discover and fix the fault! The set's been on the bench in bits for ages with only one or two minutes a day for fault finding.|
If I were a TV designer I'd be really interested in using microprocessors. They add a lot of spice to basically what would be an elementary task. The first TV sets, one merely connected to the extension speaker sockets of a medium wave wireless and they only used a couple of valves and a few mechanical bits and pieces. Over the years sets have got to be incredibly complicated. Do the bosses of the companies realise their designers are taking them for a ride?
Take this giant Akai (please!). To start with it's not really an Akai. It's a Nokia....an ITT....a Salora...oh I don't know, they change their names so often! It came in with no sound. It was too big to really get to grips with on my crowded bench but I delved inside looking for a simple dry joint. There were the usual few dozen but try as I might I could find no dry joint associated with no sound.
After too long I rumaged around the front of the set (out of sight as the front was very close to the rear of the bench) and I found a headphone socket. Blow me there was sound there! I looked up a circuit diagram but there are so many variants of this particular chassis I had to be content with piecing together two from separate U-View volumes. Two 28 pin chips are used to process the sound! Why!!! Sound is sound after all and you can't do too much with three inch speakers! Sound left the detector circuit and arrived at the first processor chip. Sound went from the first chip to the second. Headphone sound emerged from the second chip but no sign of loudspeaker sound. After a lot of searching and then a moment of euphoria I found a supplier listing the chips to only have my aspirations dashed by the dreaded legend "NLA". I looked in my boxes of spares and eventually found a couple of similar chips, salvaged a couple of years ago. Neither did the trick. I could have wasted a small fortune! After a day or two and wanting to get rid of the set I had a brainwave. As the picture was excellent I did the only thing possible to return the TV to society (rather than the local tip). I connected the headphone output to the pair of input pins at the audio output chip. Now by selecting the green brackets option on the front panel (via the handset) one can select headphones and use the volume up and down to fix the level. It's either that or tell the owner to chuck the set away and waive my fee.
Where is the fault? Probably the sets of bus and clock signals from one or other of the microprocessors hold the clue. I haven't got endless time to look further as the set's probably only worth 40 quid (with good sound to boot).
I currently have two brand new Thomson sets resident in the workshop. Neither look like they're going to get fixed. The man from Thomson has told the chap who sold them that they have to be modified because of a "software" problem! Super pictures but NO SOUND!!
Why can't we get back to basics?
I had a 21" Panasonic in the other week with what looked like a video processor fault. I say "looked like", because you can never be sure. It may have been an obscure capacitor somewhere or another processor chip interfering with the output of the first. I checked the price. For the 64 pin device I'd have to wait a month and it would cost the customer £75. After a week he said he'd collect the set. I bet he doesn;'t buy another Pansonic!
|The business end of the lamp, which stood on a stand was all shaky. When I'd managed to get it to bits I found a long threaded bolt, which held the circular potted infra-red element in place, was in two pieces.|
Nowadays one has come to expect pages and pages of warning leaflets with even the most innocuous cans of stuff. The above label is somewhat vague to say the least. I opened the workshop door when I tested the lamp but the wafts of acrid smoke still made the place uninhabitable for an hour or two. As it was raining I wasn't prepared to further test the lamp...outside so I'll hand the leaflet to the customer with a written warning on the invoice as I expect the smoke will be emitted for more than "the first time" the thing is switched on.
Why on earth can't they test these things in the factory and at the same time burn off the substance which emits the "obnoxious smoke", which I suspect is produced by the red paint, in which it is coated to make it look the part, burning. The things cost a small fortune and I object to being passed the buck!
The machine had been given to a customer who had plugged it into the mains only to be rewarded by a flash and a bang. He'd had been told that it had been working and was keen to get it going so he was a bit disappointed when it let him down.
The rear cover slipped off, after removing three screws, revealing a neat layout on a long thin circuit board. As it looked like a standard switching power supply I was sure it wouldn't prove too difficult to fix. The first interesting thing was that the fuse was intact. So much for fuses designed to protect equipment although I must admit that the 5amp fuse in the mains plug was open circuit. Usually people round here fit bigger and bigger fuses until they give up and bring me the results. Unfortunately though, sometimes each time a bigger fuse is inserted an extra bit of circuitry often bites the dust.
My golden rule is to have a good look with a strong lamp before moving on to the next stage. After this I have a good sniff round for any odd smells such as burnt transformer. Most faults can be found like this before switching on the multimeter.
This case was no exception. Around the switching transformer there was a charred mass centred in a ring of discoloured glue. (See Tip #5 in the "Restoring Tips" section). The glue is infamous for wrecking perfectly good equipment. When it gets hot it decomposes, by-products eat metal and the glue turns into a conductor. In this case the 300 volts or so at the chopper transformer primary had found a way to discharge to ground via an adjacent ferrite bead (see picture below..top left).
I removed the printed circuit board which wasn't easy because the two connectors carrying DC from the board had very short leads and clearly had been designed to be inserted rather than taken apart. A good look at the board revealed not one patch of glue but lots. I removed the chopper transformer and found a second patch of decomposing glue around some secondary pins as well as the primary pins. I carefully removed all traces of the glue from the transformer and found that fortunately the wires, although discoloured, were still intact. I scraped away some grey dusty substance and retinned the pins. Having removed all the blackish glue traces from the circuit board under the transformer I was able to remove and identify a diode with a green crystallised wire at one end. After treating the board around the transformer area with MEK, I fitted a 1N4005 in place of the 600volt 1amp Japanese type. The ferrite bead component, I repaired by cleaning away corrosion, tinning and resoldering. I then refitted the transformer and looked at the other glue infected areas. One, near the mains input circuitry, was a pool of dark yellow and had a tinned copper wire link through the middle. The wire was now devoid of tin and looking a bit thin in the middle. After scraping away the glue it looked serviceable. Another area was over the top of some tiny little resistors at the output end of the board. This was still partly flexible and I was able to tease it all it off with the help of a scriber tool. Other lumps of glue were still flexible and easily peeled off.
Underneath the board, apart from one connection to the diode, which had lost its solder to the voracious glue, all looked nice and shiny with no stress cracks in any of the solder joints.
Fitting a new fuse in the plug and reassembling all the bits and plugging in proved the FAX machine was back in business.
I noted a warning message about fitting the paper reel. This is due to design weakness whereby if the free end of the paper has any tendency to roll it is drawn back into the machine where it wraps itself round the exit roller instead of feeding out.
If I'd bought the machine I may have been tempted to write a letter of complaint to BT but as this sort of repair pays for bread and butter I don't really care one way or another!
|The owner arrived with this machine tucked under his arm. "No picture", was the complaint so I thought it would be a simple head cleaning job. No such luck! While the owner was telling me about the VCR I inserted a tape and checked for a picture whilst making a mental note that there was no display on the front panel. Sure enough there was no picture. I pressed eject and there was that nasty noise of a tape being scrunched as it came out. I took off the top cover and jiggled the half load arm to find it was lubricated with treacle. Confidently I said come back tomorrow as I'll have to fix the arm as well as clean the heads. I ordered a new pressure roller to make a good job perfect and put it on one side. When he'd left I sniffed the air thinking the last visitor had been fiddling with his tractor as there was a dieselly smell in the air. The aroma hung around and by the next day had gone away. I removed the half load lever and cleaned and lubricated the shaft then refitted it. I'd checked its height with a vernier and was confident when refitted that no adjustment would be needed. After fitting the new pressure roller and giving the video drum a good clean I plugged in and of course got no picture. That dieselly smell was back. Well he had brought the VCR in tucked under his arm so I didn't think more about it..... Now why no picture? That dieselly smell was familiar. It was more like ammonia. I sniffed around and discovered it was strongest over the metal cased power supply. I remembered where I'd smelt the smell before. Canon camcorders! It was leaky capacitors. I removed the power unit and with some difficulty unsoldered the metal plate covering the circuit board. What a sight met my eyes. The board was smothered in electrolyte. Three electrolytic capacitors were bulging and two ceramic ones were loose inside. For some reason Sony not only solder down the metal lid of the PSU box they also glue the electrolytics together making it a really annoying job to get them out.|
I removed the three offending capacitors together with the two loose 10nF types. On the side of the electrolytics was the name "ELNA" with the words "Long Life" adjacent. What does that mean? Did they test them and if so for how long? Certainly not for long enough to claim "long life" unless their other products are even worse than these or Sony design engineers don't know what they're doing!! I then spent half an hour fuming and being fumed at cleaning away the gunge. The electrolyte had not only dissolved several inches of copper track it had actually eaten away some of the circuit board itself leaving a hole right through. I've never seen one this bad. An hour or two later I'd fitted replacement capacitors and used wire links to replace missing track. Loosely coupling the PSU to the VCR I was rewarded with a good picture but still no display.
I extracted my U-View book of circuit diagrams and turned to SLV715. No neg 30 volts which stacks up with the no display fault but no circuit diagram of the PSU!! What really annoys me about these otherwise excellent books is you have to thumb through the book to look for bits of circuit common to other models. There's usually a key and often the pages you need are not far away, sometimes in the previous volume and sometimes, like this example just MISSING! Everything else was included but only a square outline for the PSU. I looked in my fault-finding guide and found "D208 probably faulty". On the circuit board marked "D208" is a small glass diode with undecipherable lettering and a conventional diode marking next to the track. The U-View info said (under the critical components list) it was a 5.1v zener...strange. I measured it with power on and it read 12 volts. As it was Saturday afternoon I gave up and locked up the workshop....
Why can I never buy the right set of bits? Most suppliers don't stock the Philips repair kits containing the little bits and pieces one needs and trying to find the right kit takes forever. When a kit arrives it usually has one wrong part as the funny cam thing is different for different models. Last time I had to wait weeks and weeks while the kit with the right selection of parts arrived as a special order. The alternative was two kits with many bits in them not required. I can't seem to get just the individual parts I need. Is it that Philips can't sell some items so they package those with the ones you need and jack up the price? And while I'm moaning about things, "Kit L" means absolutely nothing to most people.
Have you noticed (this is addressed to over-worked repairmen) say for example, when you buy a Grundig spare part and it comes in a box, what's inside is exactly the same as a pattern part (not in a box). By my reckoning the box seems to cost more than the part inside. Although... always check first, just in case! I bought a pressure roller for a Grundig (turbodeck) VCR yesterday. The Koenig pattern part cost more than the genuine Philips part! I bought the latter and saved a couple of quid.
I just opened up a Ferguson TV and removed a high frequency transformer. This particular chassis makes me mad. Quite apart from the following problem which I'm about to describe, the set is plagued by dry joints which have corroded and refuse to cleanly resolder. Anyway, there's this transformer which always fails so this time I thought I'd examine one in more detail. It's wound on a former over a ferrite rod a few centimetres or so long, and the plastic former and moulding has a dark reddish colour. Two windings are fitted. One made from thicker wire with three sections in the centre, each about 56 or 57 turns. The other made from thinner wire which has its two sections straddling the centre sections. I counted 446 turns at each end.
The problem is that the transformer gets hot and the enamelled covering over the wire deteriorates. Failure is certain because the two parts of the larger winding connect via two parallel wires running along the former, underneath the centre winding. These wires are uninsulated except for their enamel and the wires for the two windings are therfore in intimate contact for a length of an inch or so and over this length pass at right angles, probably 100 turns of the smaller winding. The enamel is in poor shape because of heating and cooling fatigue over the life of the set and therefore you get leakage between the primary and secondary. In this example I measured a couple of hundred ohms in its cold state. As the device warms up you get different results. On the screen of an affected set you get width and EW variations. Some sets blow up various circuit elements such as the TDA4950 EW correction chip.
I think whoever specified or designed the transformer should be made to pay for the repairs to these sets. I'd imagine taken together repairs would account for millions of pounds and those sets not repaired would be chucked away, either by their owners or the repairmen who can't get a replacement transformer. Up to know I've had to scrounge a transformer from a duff set and put up with intermittent results. Now I'm contemplating rewinding the old transformer but adding a layer of tape between the offending wires.
As a postscript my home-made transformer didn't work. I couldn't find the right gauge of wire and despite fiddling for ages didn't succeed AND blew up another TDA4950. After scouring the Willow Vale CDROM I found the right Ferguson part code and ordered two from CPC. The set worked perfectly and I sold it the next day. Unfortunately.. I agreed to take £20 now and £20 next Monday. That was weeks ago and I'm still waiting.....
As business was at a low ebb I decided to tackle one of the least repairman friendly things I've come across
This is a Tuner-Amplifier in a flat case using a very heavy toroidal mains transformer. The problem was slipping drive belts. Although this is a frequent problem with VCRs because their belts either stretch, decompose or develop cracks and break it's very rare that a radio is totally disabled because of this fault. The belts operate volume, bass, treble, front speaker balance and rear speaker balance. Why there aren't just five knobs I don't know! Anyway, I reckon to change the belts properly would take the best part of two days because the things won't come off without a major dismantling exercise. In this model, every effort has been made to keep the equipment as flat as possible and seemingly no effort has been made to make the thing serviceable. My E-Mail to B&O resulted in a reply in German, after I'd already fixed the tuner/amp and after I'd decided to tackle the job, and because of its age and general condition, try and keep the repair reasonably cheap. The box has a top panel in three parts: one carrying a row of aluminium leaves, under either end of which are simple leaf switches; a perspex cover with dial markings etc: and the push buttons for speaker selection, mono etc. at the back. When one end of a leaf is pressed the corresponding switch operates and a solenoid engages a dog clutch connecting a small pulley to a concentrically driven rod. A drive belt connects the small pulley to a second, larger pulley which turns a bank of pots, for example those for volume control. Coupled to each of the second pulleys is a plastic band with an indicator marker, viewed through the perspex top cover, calibrated 10 - 0 -10 . As a particular solenoid is activated the appropriate clutch engages and a motor at the end of the operating rod is powered up. The rod passes through the solenoids, one end being located at a removable bearing on the side of the main assembly and the other via a rubber sleeve to the motor output shaft. It is not an easy job to change the five belts. The whole assembly carrying the pots, solenoids and dials etc. is fastened to the chassis by two screws. Only two! To ensure these don't come loose they are locked in position with loctite which of course has filled the slots in the screws making it awkward to remove them. Having pulled away the assembly which is harnessed-in without any plugs and sockets one can get to the underside and is able to physically pull a belt from its pulleys. You can't remove them because the plastic bands driving the dials would have to removed first. As these looked a little fragile, and anyway, it would still be difficult to get the belts off because of the proximity of the banks of pots running through them, the plan was to cut each belt, remove a section, then superglue it back together. I could not match the belt, which I reckon was 55mm diameter and 1.5mm square cross-section, with my suppliers' stock anyway so replacements would have been awkward. Before a belt can be cut and rejoined its tension must be relaxed, so the assembly carrying the operating rod and clutches has to be removed by detaching the fixed bearing at the end, pulling it away from the motor, and withdrawing it. Sharp scissors were best at cutting clean edges. By trial and error with the first belt I found that a loose fit round its larger pulley was ideal. I had to mark one side of the square section belt before cutting so I could glue it back without a twist and I needed a small crochet hook because belts kept dropping inside behind their larger pulley and I would lose an end. In order to glue satisfactorily I had to use an eyeglass to see that the rubber belt ends lined up accurately. Fortunately rubber is a close second to fingers when it comes to the efficacy of superglue and the joined belts proved to be very strong. Having treated the five belts, the rubber of all of which was in good condition, the assembly carrying the clutches with the concentric rod had to be guided back into position using a large crochet hook to thread it through the five belts. It all went together. I had to hack away the loctite before I could re-use the securing screws and before I completed reassembly I decided to replace two dial lights which were out. These turned out to be wired in series, in pairs and only one needed changing. Half the lamps are inaccessible because their detachable sockets are fouled by the fragile plastic dial bands, so one has to resort to bending metalwork to get them out. The lamps are push-in types and have become jammed in over the years. I fitted a long life wire-ended replacement, soldering it to the lamp socket pins. Finally I had to file the tuning knob skirt as the metal cover, glued to a flywheel had shifted its position, making it lopsided. Such was the tolerance provided between the knob skirt and the top of the case, turning it resulted in a graunching sound. Filing it to give extra clearance cured this. It all worked perfectly after I had screwed it all back together. Installing it must be a pain as the speaker connectors, aerial socket, and input-output sockets are underneath the box. I don't know how much the thing cost when it was new, I'll ask the owner when he comes to collect it.
On the main circuit board is a tuning module which has three sub-miniature capacitors. These are the ones that leak, and in this condition seem to behave like primary cells. Having leaked electrolyte onto the circuit board, without anyone finding out, an action is set up which transfers copper from anything connected to the capacitor. This is electrolytic action (presumably that's why they're called "Electrolytic Capacitors"). The action takes place on the circuit track and the pins of integrated circuits to which the tracks are connected. Eventually the set will go wrong. In the example on the bench today, one of the pins of the memory chip was eaten away at the point where it disappeared into the case of the chip. The set would not recover tuning settings and would only give a picture if a tuning cycle was set up. It would then not store the result, or if it did, the memory wasn't readable.
A new module, type SBXM903A, is available but typically priced at £44 plus VAT. Given that there are 50 pins securing the module, the repair is not cheap. No-one would pay £80 to £100 for such a repair.
In this instance I had quoted £30 to replace the capacitor, not thinking the memory chip was damaged, and then, when I found out it was, quoted £35 because I priced the "P" version rather than the "FP" version. The latter, surface mount version was not available from my usual supplier and would cost too much from another. The cost of the labour to change the chip would need to be added anyway and, as the track was corroded, tackling the repair would be risky if it was open circuit.
I chose to follow the (basically) labour only procedure outlined below. If you have good eyesight and a steady hand it's worthwhile, if not don't even think about it.
Remove the tuning module, 50 pins taking great care as the tracks on the circuit board are THIN. I used a Denon desoldering gun.
Identify the faulty capacitor; in my case it was the 22uF one (in another set I did, it was the 0.47uF)
Confirm continuity of visibly damaged tracks
Examine the pins at the case of the memory chip, (M58659FP)
If any are badly corroded, carefully scrape away any oxide present down to bare copper.
If there is a break, using a sharp object (e.g. a sewing machine needle) prick away the case material at the damaged leg
Expose a roughly square area of copper stub and scrape it clean (it will be about 0.5mm square at best)
Push the leg close to the chip body into contact with the exposed stub
Apply solder paste
With a needle point iron, not too hot, flow the solder paste over the junction
Apply solder paste to other bared pins and flow the solder over these as well in case corrosion continues
Check continuity between the chip and the remote ends of the connected tracks
I needed a 1.5" focal length eyeglass to see what I was doing and a lot of light
Fit a new capacitor
Refit the tuning module (solder its 50 pins)
Cross fingers and switch on and test the set
I've no idea if the corrosion has stopped so I may get the set back. It's a gamble.
I once read an article that said to change ALL the electrolytics on a particular circuit board. I think there were 59 of them, or anyway a very large number. When I'd finished, the camera had exactly the same fault as it had before I'd started so I gave up.
Now I turn away Camcorders.
|This very compact VCR uses plated through holes that go open circuit. I have fixed one or two but they usually bounce. As there's hundreds of plated through holes I wouldn't recommend taking on this model.|
|I hate doing these. When you've finished overhauling this particularly crude mechanical deck with its weird shaped levers, gears and cogs and you find it's got worn heads you could spit. Heads are astronomically priced for many models using this deck. Ask what the picture was like before it went wrong first! Changing the pressure roller is also not to be taken lightly. If the plastic in the deck has gone brittle it can turn a fiddly job into an impossible one.|