University Graham valve tester Model TVT

General Notes

The TVT is an Australian made valve tester introduced in the late 1950s and marketed for a number of years. It is a rugged unit, with little to go wrong, intended for radio and TV servicing rather than to measure valve characteristics in a laboratory. A similar model, the TST/2, was available that also included a multi-meter section in the same case. The space for this can be seen at the top left hand side of the front panel and the TST/2 is also shown in the advertisement link below. The original cost of the TVT was about GBP45 and GBP58 for the TST/2.

I have included the TVT on this site as there seems to be little or no information about it on the web.

The unit has sockets for the American type valves generally found in Australian domestic radio and TV sets; namely UX4-7, International Octal, Loctal and the B7G and B9A miniature types. There is a row of three empty positions for additional socket types. It caters for 20 different filament voltages. Essentially the unit tests for filament continuity, internal shorts and emission, these being sufficient to check whether a valve is satisfactory for normal radio use. A comprehensive list of settings for about 1000 valve types is supplied as part of the manual. With this to hand, the unit is simple to use. No mains switch or pilot light is fitted but could be added.

Click to see
The circuit diagram. In later models the Merit switch is rewired so it isn't used for the Shorts test.
An advertisement from the July 1959 issue of Radio, Television & Hobbies

Collectability

The TVT is not really a collectable item in itself, but is a practical piece of equipment for enthusiasts working on valve radios as it is a reasonably priced and effective unit.

Transconductance testers such as the AVO Mk IV or CT160 are much sought after, particularly by audiophiles who require closely matched valves in amplifiers, resulting in them often fetching very high prices. A TVT, although apparently not very common, can be acquired for a small fraction of the price of these precision units.

Value is affected by general condition and a manual with settings is almost essential to give the correct 'Range' setting. The manual, if missing, can probably be found on the internet or from a fellow enthusiast.

Current Condition

This example, Serial No 792, is in quite good cosmetic condition with the front panel looking as new. The steel case has minor signs of rust seeping through the paint and the odd scratch. It was a later production unit as can be seen from the meter style in comparison with the 1959 advertisement. Despite what my manual says, the circuit has been changed so that the Merit button is not used in the Shorts test.

Work done after acquisition included some cleaning, switch lubrication, replacment of two missing knobs and obtaining the manual, which was found via a newsgroup. On testing, I discovered that the Shorts test showed a bit of leakage with some electrodes when valves were hot. The fault was traced to the 0.05mf capacitor (see circuit) which measured 0.2mf, allowing enough valve current to flow to partially light the neon bulb. The capacitor was replaced and it now works well.

I no longer have this unit as I have two other testers, so can give little more detail than is on this page.

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Page maintained by Simon Buxton VK2UA . Created: 10/02/02 Updated: 8/04/2008