Ferguson 213RG

 This rather fine looking compact radiogram arrived in the radio workshop with a Philips 341A and a Rolland/Sobell radio in March 2015 for an overhaul.

 Like the other two sets it was bought from an auction house and was missing its mains lead which had been cut off. The only advantage in this is the price because testing these things normally costs the auctioneers at least £10 which is generally added to a small reserve and can artificially triple the price.

This Ferguson was released in the UK circa 1948 and probably sold for around £30

This switch at the rear was added by a previous owner.. purpose unknown.

Below is the license plate

   

 The record player was designed for 78 RPM records and uses a metal needle rather than the later type of fragile stylus.

As a number of long springy metal clips and wires were lying inside the case I'm a little concerned that repairs will be needed to the record player.

 Removing the chassis from the cabinet was messy as bits and pieces dotted around the innards are wired together without convenient plugs and sockets, meaning several wires needed to be cut before the chassis can be sat on the bench. The secret is to leave half an inch of wire so the sleeves can be matched when refitting.

The set has been dismantled before because whoever did it trapped the audio lead from the record player under one of the chassis brackets. This had two effects.. one was to glue the chassis to the woodwork and secondly to completely flatten the cable. I didn't test the set before dismantling so can't say whether or not the audio sounded thin. Note one of the later findings when an intermittent short was found in a cable.

The valves you can see below were in very good cosmetic condition and everything is very clean and rustfree because, of course the interior of the set is sealed.

Valve line-up is slightly unusual being:-

Frequency changer CCH35; IF amplifier EF39; Detector/Audio amplifier EBC33; Output CL33; Rectifier CY31.

If you're not entirely familiar with valve coding; the common valve heater is rated at 6.3 volts and 0.3 amp giving "E" for the first letter in Mullard coding, however AC/DC sets tended to use 0.2 amp heaters and the code letter for this is "C", hence CCH35 is the AC/DC version of the ECH35. For some strange reason the EF39 and EBC33 use 0.2A heaters and yet are coded with an "E" rather than a "C". Strictly speaking the CCH35 has a 7 volt heater not 6.3 volts; the CL33 heater is rated at 35 volts and the CY31 has a 20 volt heater. The rectifier is designed to be used in a series heater chain and because of this has an indirectly heated cathode with sufficient insulation to cope with the HT present at its cathode.

Because this set is AC only rather than AC/DC one might assume it uses an isolating mains transformer, however this is not so. The radio chassis is the Ferguson 203U which is an AC/DC design. The odd valve line-up in fact indicates that it uses the AC/DC radio chassis. The record player motor is an AC type hence the 213RG is AC only.

See the circuit diagram

 The circuit diagram reveals another unusual feature of the 213RG. Although the 203U works off AC/DC mains, and this is restricted to a more or less fixed value of 230 volts plus or minus 20 volts determined by the valve heater wiring, the 213RG has an auto-transformer (on the left of the chassis below) which allows for multiple voltage settings via tappings which allow the use of 110 to 250 volts operation. The record player motor, I notice, has a 50 to 60 Hz rating although I'm unsure of fidelity if used on 60Hz mains? Would records play at 93rpm?

The radio is designed to receive only medium and long waves. Like the Rolland set I worked on before, the dial includes B.B.C. LIGHT and B.B.C. THIRD which were introduced in 1945 and 1946 respectively. Condenser dates are missing because the originals have been replaced with those grey plastic covered examples. The sockets on the left are screwed in place underneath the record platter and are used for mains tappings.

 Below is a typical layout of parts for a postwar superhet. A nice touch is the grouping of alignment trimmers at the end of the chassis at the side of the tuning condenser. Of course, this was probably done to simplify alignment in the factory rather than forward thinking of nearly 70 years for restorers.

 Nothing special under the chassis.

You can see evidence of the repairer that trapped the audio lead in the use of Radiospares electrolytics thoughtfully re-using the clips. A rare occurrence.

I shall of course be measuring resistor values and I'll be swapping the audio coupling condenser to preserve the life of the CL33. That's the dark reddish coloured part dripping wax, under the green wire.

These condensers don't always show up as leaky with an ohmeter and this one vaguely gave about 12Mohms at DC and its wax has melted so it can't be very good. I fitted a new 0.068uF 250 VAC condenser.

Looks like a combined medium wave/long wave oscillator coil, and the RF one is on top of the tuning condenser.

The brown insulated screened cable connected to the volume control and passing over the chassis carries the audio from the record player.

 Moving on to the record player. As usual with these old mechanisms the grease is more like a brand of elephant glue than lubrication.

Also, there were two springy lengths of wire and two long springy strips in the bottom of the case, probably once fitted into the mechanism?

You'll notice the white covered cable has blue/brown wires so is not original because red/black or red/blue were used in the 40s and 50s.

 The record player was made by Garrard. As it's designed to play only 78 rpm records and cannot hold more than one record the mechanism will be relatively simple.

Presumably (from the collection of levers etc) it will have an auto cut-off operating when the arm reaches the end of the groove. As it appears a cover is missing the player might have given trouble early in it life?

 

 

 I guess this switch, on the rear panel under the identification label, was not only added by a previous owner it seems to have been broken by the last repairer, or was this one and the same person?

The wires have been cut off so presumably, whatever the purpose of the switch it was deemed to be redundant?

 

 

 

 The first job will be to get the radio working, then to find a service manual for the record player if it gives trouble, and identify the loose metal parts found in the bottom of the case.

In fact, I never did find the purpose of these. Everything worked so I can only suppose these parts are alien to the Ferguson and dropped in by someone?

The sticky lubricant will need cleaning off, but I'll only proceed if the motor is OK.

As far as a new mains cable is concerned it will be tricky to sort out wiring as one side of the mains will be connected to metalwork. I noticed when dismantling the set that wax had been used a filler in the knob's grubscrew holes. This was standard practice to prevent wet fingers from getting a shock.

Clearly the record player centre spindle is metal as is the needle and wiring inside the player arm, so the question must be "are the spindle and needle etc isolated from the radio chassis". I guess they must have been when supplied to the first customer, but what happened subsequently in the hands of repairers, and wear and tear? Read on...

I had a lull in lift repairs and gardening (rain) so I tackled the Ferguson radiogram.

Clearly someone has had a good meddle as the switch pictured above has no bearing on the original circuit, neither has a bunch of wires in the bottom of the cabinet. Presumably a failed modification? What's a bit annoying is the mains wiring has been messed around. As the set has a live chassis this is not good. The first thing was to find a suitable isolation transformer and see if the set is serviceable. Having found one I tackled the set's autotransformer first. Looking at the circuit diagram, I identified the various wires and found the windings were all OK. The valves are wired in series and all the heaters were OK. Having disconnected the modified mains wiring I wired the 240 volt connections to my isolation transformer, plugged in, switched on and watched the valves warm up. So far so good.

I've used this old isolation transformer for decades.

It came originally from a Sony TV and isn't 1:1 as you can see from the markings. As my mains voltage can be over 240 volts I connect it in its step-down configuration. If need be I also have a special variac wired to provide exactly 230 or 240 volts. See this variac.

 Before going further with the story, I'll add that it's imperative to check a few things before applying power to an old radio. In this model the loudspeaker carries the output transformer and this has to be disconnected to allow the chassis to be easily removed from the case. It's essential to reconnect the transformer primary otherwise the output valve screen grid will draw excessive current and damage the valve. It's also advisable to check that the HT line has a decent resistance to ground, say 100Kohm or higher. If it's low, check the circuit for a reason. If there's no apparent reason find the part that's shunting the HT line. The third item to deal with is the condenser between the anode of the audio amplifier and the grid of the output valve. Don't bother testing this, just remove it and fit a new condenser. Even several megohms leakage in the coupling condenser can forward-bias the output valve and ruin its emission.

When re-connecting the loudspeaker, I wondered if the disconnected switch was something to do with an added extension loudspeaker? If so someone hadn't realised the loudspeaker metalwork was connected to mains, although there's a flying lead for this purpose which fastens under a nut securing the speaker chassis to the cabinet. Anyway, it's not good practice to add an extension speaker to a live chassis radio unless you know what you're doing.

After waggling the wavechange switch and the radio/gram switch the set burst into (intermittent) life. A squirt of switch cleaner sorted out the intermittency.

Because I'm using an isolation transformer I was able to connect a signal generator. I found the IF of 470Kc/s had drifted and, after twiddling two trimmer condensers (C10 & C11) at the top of the IF transformer can, and the slug of the coil (L9) in the centre of the chassis, the set became quite responsive to broadcast stations.

Next, medium wave alignment. This was tricky because the data sheet tells one to adjust three trimmer condensers but fails to identify them explicitly. C4, C5 and C14 are in fact the local oscillator trimmer, RF trimmer and oscillator padder. Long wave alignment uses C16, C3 and C15 which provide similar functions. It was quicker to use trial and error to identify these six trimmers which are all mounted at the side of the tuning condenser. Ordinarily, padding is carried out by altering inductance, but in this set the designer used trimmer condensers to the same end.

Alignment was straightforward and the set was clearly in no need of further work in respect of parts. In fact plenty of stations could be heard without an aerial.

I decided to test the gramophone. This uses a metal needle which felt very sharp. The pickup carries a lead with a red and black inner within an outer braided metal shield. There's a small mains connector block adjacent to the arm which serves to permit a 100-130/200-250 voltage change. This block carries provision to connect a pair of coils in the motor either in parallel for 120 volt mains or in series for 240 volts..

 

 

 The meddler I mentioned earlier had connected a new mains lead into this connector block. In doing this the securing screws had been loosened so I removed the modification and connected a new length of cable which connects to a choc block. This also connects to the cable from the on/off switch at the rear of the volume control and a new 2-core mains cable. Mains voltage can be selected via a crude plug and socket arrangement under the gramophone turntable, where a green wander plug is inserted in one of four mains tappings on the autotransformer.

Switching to gram from radio resulted in horribly distorted playback from an old 78 rpm record.

I connected an audio signal generator instead and found results were very good.

 

I fitted a brand new metal needle and this fixed the distortion problem.

Top is the old needle and bottom the new one.

 After tidying up the wiring I refitted the chassis and speaker into the cabinet but, before fixing the gramophone deck, I decided to check for mains safety. With 3-wire mains cables safety checks are made by measuring the earth pin to exposed metalwork resistance. This should be very low. This set uses a 2-wire mains cable so safety testing can only be done by measuring the resistance between the mains plug live or neutral to any exposed metal parts. Live chassis radios use wax infill to insulate the grubscrews in the knobs and little else in the way of metalwork is generally visible, however this set has a gramophone which uses lots of exposed metal parts. Oh dear...all the gramophone metal parts measured only half an ohm or so to the mains plug neutral pin. Something is seriously wrong as surely even 1940s designers wouldn't have had live parts accessible. You might suggest that mains neutral is close to ground and it doesn't matter that mains neutral connects to exposed metalwork, however, when a set such as this was used it was common practice to plug it into a light socket multi-way adaptor. As a lamp adaptor is not polarised you could plug the radio into the socket such that live mains connected to the chassis.

The circuit diagram shows the chassis is connected directly to mains neutral. The turntable has a motor whose windings are insulated from metalwork. The pickup connects to a pair of wires (red and black) inside a screening sheath. The metal sheath is not insulated so is in contact with the pickup arm metalwork through which it's threaded en-route to the pickup. The wires and screen are terminated at the gram/radio switch which is positioned in the corner of the deck. From the switch is a black wire going to the pin marked "E" next to the aerial wire marked "A" on a small paxolin panel at the rear of the cabinet. This earth wire connects via a wax-covered condenser (which tested leakage free, but which I'll change later anyway) to the chassis. There are two screening braids terminating at the switch. The first braid covers the red and black wires connecting to the pickup and the second braid is connected to the black wire from the pickup. The first braid which is mainly uninsulated, connects the "E" connection to the pickup and the deck metalwork and the second braid is (live) chassis ground.

 

 

Above:  Left is the pickup removed from the arm.

The red and black wires are soldered to the coil connections.

The braid connects to the metal body of the pickup assembly.

 Below:: The picture on the left shows the end of the cable going to the pickup coil disconnected from the gram/radio switch..

I found this section of cable carrying the red and black wires was faulty. The black wire rubber insulation had perished and this had resulted in a short between "E" and chassis (mains neutral).

 

 

 Above is the condenser seen on the left. It's job is to provide a barrier between mains neutral and safety earth. You can see it's rating marked "1000 volts DC".

It's also marked 0.005uF but in fact measured 35nF which is 0.035uF so clearly not right although it measured over 35Mohms.

I fitted a new 5nF condenser marked 2000 volts.

If you're interested. What's the effect of a 35nF condenser compared with a 5nF condenser in this specific application?

Connecting terminal "E" to ground will pass some current. If the live chassis is inadvertently connected to live mains rather than mains neutral the alternating current through the condenser will be calculable. For a 35nF condenser the current will be around 3mA and for a 5nF the current will be about a third of a mA. These currents represent a tingle felt by a user connecting "E" to ground via his fingers. The higher value might be unpleasant hence the need to fit the correct value of 5nF.

I need to replace the cable. Not an easy task as the overall diameter needs to be relatively small in order to pass into the pickup arm. After much thought I found some miniature coax used in an old audio cable. I fitted two screened cables, one for the red wire and the other for the black wire. At the switch end the black wire connects to the screened cable connecting to the volume control and the red wire to its centre conductor.

Below the old and new wiring to the pickup.

 

 

 Next, I'll have to carry out a second safety test then check that there's no hum.

Refitting the chassis and all the other parts was not easy. It took two to lift and position the bits and pieces, chassis, loudspeaker, record player deck etc.

 Below is the refurbished Ferguson. You can just see the green wander plug for setting mains voltage under the front of the turntable.

All the knobs have wax filling over their grubscrews.

 

The finished set with a new 2-wire mains lead with moulded plug. The quality of the record player isn't wonderful and will need a supply of sharp needles.

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