This is some of the Test Equipment I use every day

 I wrote this in 2001 and since then things have changed a little. I added the spectrum analyser in 2014. I still use the AVO valve tester, but I prefer to use a Black Star audio signal generator, my Wavetek RF digital signal generator and a new digital oscilloscope. The line output tester is completely obsolete as are the TV sets it used to help repair, but I still wheel out the variacs from time to time.

Rigol DSA-815-TG

 My new spectrum analyser which covers up to 1.5GHz (click picture to see more)

Note the invisible leads...

GDS1102U Oscilloscope

Note again the invisible leads... Click picture to read its spec.

AVO Valve Tester

 Here's my old AVO valve tester which is virtually indispensable unless one has loads of valves and plenty of time to swap them around. It was used by Electronics Lincs in North Thoresby to test TV valves and it's still got its original handbook.

The handbook is vital as it provides the settings for the tester. The array of switches and knobs needs to be carefully adjusted for each valve being tested. Under the lid is a set of valve bases and the pins on these are connected to roller switches which are turned to a number 0-9. These switches set the valve electrodes correctly, after which the various voltages are set up, the heater or filament, anode, screen etc. Depending on the type of valve other switches and knobs are adjusted so that emission and gain can be checked.

Weirdly, the equipment uses AC not DC to power the valve being tested.

RF Signal Generator TF2008

 This is a Marconi TF2008, one of the last analogue professional products of this type from that company. It uses transistors (not valves) of course and can do most things. One really needs a counter to check exact frequency output but it has a built-in device to carry out spot checks if one isn't available. The first counter I had was cheap and cheerful and had one significant leaked RF so that the superb attenuator ccould't be increased beyond background level of the leak. To get down to microvolts required the counter to be unplugged.

The generator has one really unusual feature. The pointer traverses to the right going from zero frequency to the top of the first band then, when the next band is selected, it tunes "backwards" from right to left, next tunes "forwards" from left to right and so on in 12 bands to over 500MHz. This gives you essentially a continuous tuning scale of about 12 feet in length.

I bought it in a "non-working but easily repairable" condition years ago for a lot of money. I think mine had been connected to a transceiver which had inadvertently been put into transmit mode, damaging the output of the generator. I find it nicer to use than a digital equipment but a bit fiddly when setting to exact frequencies. This is probably because I use a digital counter with too many digits.

See repair tips and Instruction Manual

Audio Signal Generator TF1370

 This was my first audio signal generator, a Marconi TF1370 which is authentic enough to use valves but suffers from the drawback of having to warm up.

Tektronix Oscilloscope Type 454

 I can't abide an oscilloscope which takes hours to warm up and stabilize so I ditched the various valved models I had and invested in this Tektronix for which my bid of £50 was accepted, being surplus to Plessey's requirements. It's transistors warm up immediately and one can make measurements within half a minute of switching on.

I no longer use this because I bought a brand new scope (GDS-1102U) when the supplier listed them at reduced price for a short period in September 2013. I paid £276.94 inc VAT and delivery.

Pricing of products such as this is sometimes very odd. For example, in Dec 2014, Farnell lists the GDS1102U for £568 whilst sister company CPC has them at £383. Maplin has them at £419.99, whilst Amazon lists four at £908.50, £509.99, £761.10 and £481.60. Ebay has them at £438.70, £678.29, £436.38 and £627.41. A US company has them at $488 which is £312 and in South Africa they are £418.

What on earth is going on. Can anyone offer an explanation?

The new model has some really useful features which were undreamed of when Tektronix made the model 454. I can press a button and immediately see a locked stable picture of the input just the right size for the screen and another press I can see the RMS value of a sinusoidal input.

Line Output Transformer Tester


 This is my Line Output Transformer Tester.

The key part of all TV sets is the transformer which develops the high voltage to drive the cathode ray tube. The LOPT, as it is known, is also pressed into service to provide subsidiary voltages for many other parts of a TV's circuitry. Energy that would ordinarily just go to waste as heat is harnessed to provide things like power for the CRT's heater, voltages to drive the focus and screen grisd electrodes, and several low voltage power sources. The LOPT is very highly stressed and a typical fault is a breakdown within the transformer's windings. This is usually not an easy fault to diagnose, at least it's one that could be mistaken for an entirely different fault. The simple way to find out if a LOPT is faulty is to swap it for a new one. Unfortunately as there are hundreds of different types it would be an expensive proposition to carry stocks of all of them. One of the largest manufacturers of transformers came up with this little tester which can accurately diagnose most LOPT faults by emulating the circuitry connected to it in a way that can determine short circuits between windings, shorted turns in windings and faulty rectifier diodes in the EHT circuit. Since I started using it I must have saved many hundreds of pounds in transformers I never needed to use.

It's now many years since I used this.


 This is a government surplus variac which is essentially an auto transformer which one connects across the mains supply to provide an adjustable source of power for testing faulty TV sets and the like.

I've had this one in the workshop for ages on loan but recently swapped it with its owner for a TV repair.

By monitoring input current, usually across an open fuse holder one can gently increase the mains voltage and check nothing nasty is afoot.

Be warned though with TV sets the degaussing posistor presents a low impedance across the imains input until after a second it gets hot and effectively disappears. As the control is turned up it is customary to pause while the posistor gets to operating temperature bedfore looking for meaningful input current.

This particulatr variac has plenty of power handling capacity unlike my previous model which I bought from Maplins which blew up after only a couple of uses.

I've now fitted this device into a case.

Another Variac

 This is another variac. It was being chucked out because the owner didn't know what it was. Inside the home made wooden case, disguised as metal, is a variac with a horizontal frame rather than the vertical type above.

This model is wired in a different way to the one above. It can be adjusted to provide an exact output voltage over a limited range.

Solartron Power Supply

 Clearly designed for testing valve equipment because you can see the output for standard valve heaters (6.3v). The PSU provides outputs not unlike the Type 234A used for powering the R1132 and R1392 receivers. I recall looking inside after I bought it and found a series pass circuit using power valves to give a regulated output.

It uses five valves, a pair of 5B/254M beam tetrodes for output control and three diode rectifiers, type EY84.

See a new power supply I'm building
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