Noisy input on Michaelson & Austin TVA-1 - diyAudio
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Old 18th May 2010, 11:59 PM   #1
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Default Noisy input on Michaelson & Austin TVA-1


Anyone ran into this before? On the input board schematic there are .022 and 5 pF capacitors, which seem to be the likely suspects for causing a small buzzing noise being fed to the output stage. Any ideas on what other caps it might be? I know I could just replace all the caps, diodes and pots, but has anyone worked on this amp before? A service manual would be greatly useful.
Has anyone seen one available? TIA...

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Old 19th May 2010, 12:10 AM   #2
SY is offline SY  United States
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Here's a schematic:

Schematic - Michaelson & Austin TVA-1 Tube Amplifier @

The caps you mention would be unlikely suspects. What sort of buzz is it? 100/120 Hz sawtooth? Both channels?
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 19th May 2010, 01:09 AM   #3
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It's higher than 120 Hz., maybe up around 400 Hz. and it's in both channels.
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Old 24th September 2011, 09:24 AM   #4
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Please check the grounding which is highly possibly the cause of the hum.
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Old 24th September 2011, 12:11 PM   #5
DF96 is offline DF96  England
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Yes, if its on both channels then either grounding or something in the PSU.

Blindly changing caps etc. is a good way to introduce new faults. If your doctor tried to cure you by just working though all the common medicines at his disposal you might be concerned; diagnosis ought to precede treatment!
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