Valve Testing

If you have any old valves knocking around that you don’t know whether they are working, then you may be interested in using Mullard_valvesmy valve testing and grading service to save you money.

With my Sussex valve tester, a modern digital IMG_3858equivalent to the famous Avo CT160 I can check a valves operating characteristics. This applies to the all valves that commonly find in guitar amps like EL34, 6L6GC, EL84, ECC83 and other more unusual ones like you find in old Ampegs and WEM Copicat. Actually, the range of sockets that can be tested is into the 1000s.through the use of adaptor cables.

Applications

Sorting pre amp tubes for high gain
Identifying pre amp dual triode with closely matched gain for using in the phase inverter position.
Checking old power valves and identifying any ones with some life left.

Pricing – it’s just £2.50 per valve star2.50each3

You can either drop off valves when you bring in your amp for servicing or repair. Alternatively, you can just drop them off in person most evenings after 6pm.

You can post them to me if you are further a field. Using royal mail signed for service this costs about £7.50 each way for a box of ten valves.

Please bring your valves in a sturdy cardboard box or plastic container (takeaway food containers) to protect them. The valves will returned after testing numbered and you will receive a written report indicating their results in a user friendly format.

Unfortunately testing does not fully guarantee valve audio performance, for example micro-phonic noise will not get picked up by these tests.

Checking the valvevalve matching

  • Checks for shorts between electrodes
  • Valve gain or to give it’s technical term the mutual conductance or gm
  • Current draw at max gain – old valves max current draw tends to reduce over time.
  • Heater continuity
  • Gas leak

Notes:

  1. Rectifier valves, like GZ34 can be tested but test conditions as strenuous as in an amp can not be simulated.
  2. Checking the operating conditions allows you to grade valves but it does not identify noisy or microphonic valves.