This is some of the Test Equipment I use every day

 I first wrote this in 2001 and since then things have changed quite dramatically. 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. I'm adding various other things that have been languishing on shelves, mainly unused as I add them to my inventory.

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Rigol DSA815-TG


GW Instek GDS1102U


AVO Valve Tester 

Marconi TF2008


Marconi TF1370 

Tektronix TYPE 454








Solartron SRS15.2 

Philips PM6611

 Racal 9915

 Fluke 1953A

 Racal 1991

 Farnell FG3

 Wavetech 2407

 Hewlett Packard 431C

 Hewlett Packard 3200B

 Power Unit 234A

Datalab Transient Meter 


 Testing this sort of circuit board involves lots of test equipment, some of which comes in very useful for fixing old radios.

Click to see a selection.


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

See repair tips and Instruction Manual

 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.

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


You can judge when I started this website! 

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 type SRS153.2

 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 provide a variable output voltage.

It uses five valves, a pair of 5B/254M (CV428) beam tetrodes for output voltage control and three diode rectifiers, type EY84. As I recently (2019) needed to repair this equipment I checked the circuit details. The two 5B254M valves are connected in a series pass circuit with their anodes supplied by two HT rectifiers in a full-wave swinging choke arrangement with the HT transformer centre tapped to ground. The third diode rectifier cathode is fed from the same HT transformer winding to produce a high voltage negative supply. This is filtered through a pair of capacitors and a 470Kohm resistor to supply a bias voltage to the grids of the 5B254Ms. The HT output voltage is determined by the setting of the slider of a potentiometer wired across the HT and the bias voltage. All nice and simple and extremely rugged and straightforward when compared with its modern solid-state equivalent.

When mine failed, due to connection across something modern that happened to fail short-circuit, the excess current through the 5B254Ms resulted in failure of screen grid resistors. One burnt up and the other went high in value. These appeared to have once been 47ohm resistors. I fitted two new resistors plus two new anode "stopper" resistors which had risen in value from their marked 100 ohms. The 1Kohm grid resistors were both a bit high at 1.5Kohm but as they're not critical I left them. There are a couple of cathode resistors which are high stability 10ohm ceramic bodied components in perfect condition. The failed anode and screen resistors were very low wattage and perhaps chosen as such to act as fuses in the event of an overload?

See a new power supply I'm building

Here's some pictures of the inside of the Solartron SRS153.2





 This is the best example of the circuit diagram I could find, but as the circuitry is so simple you can easily follow it.


 It's often useful to have two independent HT power supplies and I was pleased to receive this second Solartron (above) from Steve Kaplan. This model looks slightly newer than my first example, having a different meter. He also presented me with this oscilloscope.


 Philips Frequency Counter type PM6611

See the Advertising data...

 The Philips PM6611 has a single input connector which accepts up to 80MHz with a sensitivity of a nominal 10mV dropping off at higher frequencies. Input impedance is 1Mohm and some switchable signal processing which helps it accept either sine or square wave inputs and improved performance below 100KHz. In practice this example handles inputs at over 100MHz.

 Racal Frequency Counter type 1991

See the operators manual

 The Racal 1991 has two input sockets, 0-100MHz (Input A) and 0-160MHz (Input B) with sensitivities of 25mV rising to 50mV towards the upper frequencies. Input impedance is selectable at 1Mohm or 50 ohms.


 Fluke Counter type 1953A

See the user manual

 This model of the Fluke 1953A has three input sockets designed to accept 0-25MHz (Channel A), 0-125MHz (Channel B) and 0-512MHz (Channel C which includes a prescaler). Generally the sensitivity is 30mV, falling off towards the maximum frequency ranges. The input impedances are aound 1Mohm rather than typical 50 ohms.


 Datalab Transient Recorder type DL901

I have no information on this equipment which I bought in a job lot around 2002.

 Farnell Audio Signal Generator type FG3

See the user manual

 The FG3 is a very hand instrument providing extremely low frequency signals up to a couple of hundred KHz. It'll need an external attenuator if the variable control is found to be too inaccurate. It also has a swept output.


 Racal Frequency Counter type 9915

See the technical manual

 The Racal 9915 has a better sensitivity (down to 10mV) than the earlier 1991model above and has two input sockets tailored for up to 60MHz (Input B) and 40MHz to 520MHz (Input A). Note that Input A is rated at 50 ohms whilst Input B is 1Mohm.


 Wavetech Signal Generator type 2407

click the picture to see more

 Hewlett Packard Power Meter type 431C

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 Hewlett Packard VHF Oscillator type 3200B

See the Operators Manual for the HP3200B Oscillator

Like some of my receivers, the R206 and DST100 plus the W2508 Wavemeter, this VHF Oscillator has a turret tuner carrying coils for its different wavebands. The Oscillator has a pair of 6DZ4 valves operating as a multi-vibrator. A design weakness is the rather flimsy knob which not only operates the turret, but also flips the tuning scale to match the selected coil.

 Power Unit Type 234A

See the circuit diagram

 This is the AC power supply for the R1392 and R1132 receivers although it's fine for powering lots of wartime stuff.

Mine is missing its plug-in moving iron meter, but works OK without it. Under the light grey fuse panel lid there's a setting for changing the HT output between high and low.


A miscellany of small testers I use all the time


 Integrated circuits rarely fail when left alone, but lightning, power supply problems and of course electronic enginers or technicians can be a big influence on them.

This simple tester can evaluate the type of integrated circuit and check it functions correctly.


 One of the most useful testers ever invented, this device tells me if a capacitor has reached end of life. Much like radio valves electrolytic capacitors have a finite lifetime. This can be dramatically reduced if subjected to a high ambient temperature or if they're subjected to AC.


 I use this tester mainly for checking inductors.


 This tester tells me if a triac or thyristor is serviceable.

   Despite its vague name, this tester is for transistors including FETs, Darlingtons and insuated gate types.

   Not so much used, this tells me the characteristics of zener diodes.


 This tester has been superseded by the component tester above but was very useful when I first acquired it.


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