UK Vintage Radio Repair and Restoration Discussion Forum

UK Vintage Radio Repair and Restoration Discussion Forum (https://www.vintage-radio.net/forum/index.php)
-   Homebrew Equipment (https://www.vintage-radio.net/forum/forumdisplay.php?f=99)
-   -   Yes, yet another home made valve tester. (https://www.vintage-radio.net/forum/showthread.php?t=167502)

g4wim_tim 27th Jun 2020 8:26 pm

Re: Yes, yet another home made valve tester.
 
Interesting design for a valve tester in the latest issue of Signal from VMARS.

Page 17, Uses an AC signal and relies on the 180 degree phase shift through the valve to measure gm directly.

AdrianH 27th Jun 2020 8:36 pm

Re: Yes, yet another home made valve tester.
 
Hi Tim,
VMARS is one I am not subscribed to.
BVWS and the valve Museum are enough for now. The tester is basically done for me, the main interest was plotting or verifying the grid anode current curves and a bit of a learning exercise.

I managed to verify it against Davids Simpsons test valve, so think it is good enough for what I require it for at this stage.

Cheers

Adrian

AdrianH 30th Jun 2020 8:09 pm

Re: Yes, yet another home made valve tester.
 
1 Attachment(s)
Today I managed to get a switch that had three positions so I could do 4, 40 and 80 mA ranges.

So I used David's standard valve again and started to plot going up to 80 mA range, but after 45mA of anode current the valve would break into oscillation again, so a few hours have been spent trying to figure out why.

Then on a whim I removed the 0.047uF caps I had on the Octal pins, so now only the 1nF caps on the Banana sockets and the ferrites on the leads of course. Instant karma, no signs of instability over the full current meter range.

So for reference I did a full run entered the figures in the spreadsheet and provided plots, the valve has been getting a few hours work today, can emissions improve slightly with use?

Now to test some of my valves!

Adrian


All times are GMT. The time now is 4:28 pm.

Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.