Avo vcm mk1

[Bushbaby]

Hi All
I have realised that I have never really got to grips with testing diode or triode valves using my Avo vcm mk1. Yesterday I was trying to test a UCH42 valve and had to stop as I was fearful of overpowering it with the wrong voltage settings. I haven't got to grips where the Avo test book shows 2 sets of values for a valve such as this.

Can anyone advise please.

Thanks

Rob

[pwdrive]

So far as I can make out from the Avo valve data book the first set of voltage settings are with the anode selector set to A1 and the second set of voltages is with the anode selector set to A2, the thumbwheel settings remain the same.

Lawrence.

[Bushbaby]

Hi Lawerence
I was try this on an a potentially sacrificial TV valve such as a PCC84 or similar which I am sure I have a number of in my 'pulled' collection.

Many thanks

Rob

[pwdrive]

The anode selector switch (A1 & A2) just switches the selected anode voltage to the respective anode pins on the valve via the thumbwheel switches, for the UCH42 A1 will be the triode section and A2 will be the hexode section.

Lawrence.

[Bushbaby]

Hi Lawrence
Yes, you are correct (thank you) as I have tested this on a PCL83 and UCH42. However, the meter light bulb has failed. I hope its easy to replace?

Many thanks

Rob

[pwdrive]

I wouldn't know Rob, I assume it's a MK1 VCM and not a MK1 tester (two panel job)

Lawrence.

[Bushbaby]

Yes it's a vcm1 and not a 2 panel model.

[Bushbaby]

I havent used this in quite a while. Of course, I had forgotten to use the reset button in the event of a faulty valve being tested. The meter light is of course working having pressed the reset button. However, I'm not so sure of the accuracy of this unit - every valve anode test result that I evaluate appears low to that shown in the avo valve data manual. I was aware when I bought this that it had a problem with the negative grid volt pot being uncalibrated which doesn't help at all.

I'm not sure how to proceed any further at this stage. Any help would be most welcome.

Many thanks

Rob

[westcliff]

Hello Rob,

There are calibration instructions in the manual, if you have it. If you don't have the manual, I can scan the relevant pages for you.

Gus.

[Bushbaby]

Hi Gus,
I have just read p24 - 27 of the operation manual which is very helpful (many thanks) - I assume that you are referring to this in your post?

Regards

Rob