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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 11th Jun 2019, 8:17 pm   #1
Valveoid
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Join Date: Apr 2019
Location: Barton-le-Clay, Bedfordshire, UK.
Posts: 3
Default Avo Mk1 Valve tester

Hi there - just found this website and being an analogue man who loves reel to reel tape recorders and valve amps I thought I'd join up.

I recently picked up an ancient Avo Mk1 Two panel valve tester in good condition, got the user manual and valve data and set it up to test an EL34 valve from my Selmer Treble and Bass amp. However on turning on instead of the needle moving slightly to the right and then having to re-set it to zero using the set zero control it shoots violently over to the right and I can't reset it to zero - anyone got any ideas? Thanks in advance...
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Old 12th Jun 2019, 5:24 pm   #2
Simon Gittins
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Join Date: Jan 2006
Location: Cornwall, UK.
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Default Re: Avo Mk1 Valve tester

Hi and welcome.

Unfortunately, it could be the set zero control itself; needless to say this is a special and I'm not sure if there is an easy fix. Worth checking the rectifier in the same circuit.

Putting "AVO 2 Panel" into the search box at the top will bring loads of posts.

Hopefully an expert will give further advice.
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Old 12th Jun 2019, 8:49 pm   #3
Simon Gittins
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Default Re: Avo Mk1 Valve tester

Some relevant information from Post 8 onwards in this thread:
https://vintage-radio.net/forum/showthread.php?t=70458
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Old 20th Jun 2019, 8:48 pm   #4
Valveoid
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Default Re: Avo Mk1 Valve tester

That's great thanks! Managed to solve the problem with the needle wildly fluctuating - the Ma/V dial had been over wound so the copper connector was earthing out! I'm now getting very high (almost off the scale) readings for good EL34 valves - I'm assuming this is normal?
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Old 21st Jun 2019, 7:26 am   #5
Electronpusher0
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Location: Bognor Regis, West Sussex, UK.
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Default Re: Avo Mk1 Valve tester

Yes this is normal.
The gm for an EL34 is 11, the dial on the Mk1 (with the lower LH knob set to ma/V) only goes to 10 so the meter will be off scale on a good valve.
The trick is to try and set the knob to 11, impossible of course but set it just above 10.
The scale will now indicate "good" but should be just on scale.

Peter
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