Sussex Valve Tester blowing mA/V meter. - UK Vintage Radio Repair and Restoration Discussion Forum

n_r_muir · 8th Nov 2013, 11:57 pm

Hi,

I have been using the Sussex valve tester for about 6 months and during that time the mA/V meter has been replaced twice. I was testing a 12AT7 and it passed all of its tests for leakage and inter-electrode shorts, It even showed good emission, 10 and 11 mA. There was a brief flash over in the valve and the anode current meter settled back to 10mA but the mA/V meter is now stuck on 1 even when there is no valve in the socket.

I did not notice anything out of the ordinary the first time the mA/V meter failed. Has anyone else experienced this problem?

Are these LCD meters repairable or is it completely U/S?

Herald1360 · 9th Nov 2013, 3:31 pm

It's probably dead.

Maybe time for some input protection- limiting resistors and suitable zeners across the input and to ground/meter supply rail should do it.

Top Cap · 9th Nov 2013, 4:21 pm

I also had this problem but since fitting my diode mod I have had no failures. But then maybe I have not had a valve failure large enough to test the diode protection. Did you have a diode in place? Les

n_r_muir · 9th Nov 2013, 9:31 pm

HI,

Yes I had the shunt diode in place. The flash over must have destroyed the meter before the diode turned on.

8th Nov 2013, 11:57 pm	#1
n_r_muir Hexode Join Date: Jul 2007 Location: Edinburgh, UK. Posts: 344	Sussex Valve Tester blowing mA/V meter. Hi, I have been using the Sussex valve tester for about 6 months and during that time the mA/V meter has been replaced twice. I was testing a 12AT7 and it passed all of its tests for leakage and inter-electrode shorts, It even showed good emission, 10 and 11 mA. There was a brief flash over in the valve and the anode current meter settled back to 10mA but the mA/V meter is now stuck on 1 even when there is no valve in the socket. I did not notice anything out of the ordinary the first time the mA/V meter failed. Has anyone else experienced this problem? Are these LCD meters repairable or is it completely U/S?

9th Nov 2013, 3:31 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Sussex Valve Tester blowing mA/V meter. It's probably dead. Maybe time for some input protection- limiting resistors and suitable zeners across the input and to ground/meter supply rail should do it. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

9th Nov 2013, 4:21 pm	#3
Top Cap Octode Join Date: Mar 2006 Location: Watford, Hertfordshire, UK. Posts: 1,270	Re: Sussex Valve Tester blowing mA/V meter. I also had this problem but since fitting my diode mod I have had no failures. But then maybe I have not had a valve failure large enough to test the diode protection. Did you have a diode in place? Les __________________ Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way!

9th Nov 2013, 9:31 pm	#4
n_r_muir Hexode Join Date: Jul 2007 Location: Edinburgh, UK. Posts: 344	Re: Sussex Valve Tester blowing mA/V meter. HI, Yes I had the shunt diode in place. The flash over must have destroyed the meter before the diode turned on.