Avo Mk IV Valve Tester
 

Hi, My trusty Avo MK IV has given up. As soon as I rotate the leakage control (on any setting) the meter shows about 5 Meg leakage, this happens even without any valve inserted. If you continue to test with a valve inserted, when you select "Test" for anode current the meter goes negative. Does anybody have a service manual or any ideas? Cheers, Pete.

Re: Avo Mk IV Valve Tester
 

The working instructions are available at https://frank.pocnet.net/instruments..._Mk-IVuser.pdf

There are several experts on valve testers on this forum. I expect someone will have seen your fault before.


Richard

Re: Avo Mk IV Valve Tester
 

SOrry- just noticed you want the service instructions - not the working instructions. I do have the service manual, but at 15MB its four times too big to post on here.

What I can do is to provide a link to my copy so you can download it:

https://e.pcloud.link/publink/show?c...DmJcg6x8T09QuV


Richard

Re: Avo Mk IV Valve Tester
 

Incidentally, my guess about the leakage you are measuring is that it is caused by a leaky capacitor. I would make a start by replacing all the paper caps.


Richard

Re: Avo Mk IV Valve Tester
 

The link to the service manual provided by Richard doesn't seem to work for me. This is a link to what I gathered on the AVO Mk IV valve tester, including the service manual:

https://drive.google.com/drive/folde...ycoeVwAJHgNMSj

Re: Avo Mk IV Valve Tester
 

Sorry to provide a non-functioning link. I have just found the service manual with a file size within the forum's limits, so have attached it here in case its useful.


Richard

Re: Avo Mk IV Valve Tester
 

Thanks everybody for your replies. I shall replace the caps first, then go from there.