Noisy input on Michaelson & Austin TVA-1

pix4work · 18th May 2010, 11:59 PM

Hello,

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...

pix4work

SY · 19th May 2010, 12:10 AM

Here's a schematic:

Schematic - Michaelson & Austin TVA-1 Tube Amplifier @ AmpsLab.com

The caps you mention would be unlikely suspects. What sort of buzz is it? 100/120 Hz sawtooth? Both channels?

pix4work · 19th May 2010, 01:09 AM

It's higher than 120 Hz., maybe up around 400 Hz. and it's in both channels.

apecg · 24th September 2011, 09:24 AM

Hi,
Please check the grounding which is highly possibly the cause of the hum.

DF96 · 24th September 2011, 12:11 PM

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!

18th May 2010, 11:59 PM	#1
pix4work diyAudio Member Join Date: Sep 2009	Noisy input on Michaelson & Austin TVA-1 Hello, 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... pix4work

19th May 2010, 12:10 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	Here's a schematic: Schematic - Michaelson & Austin TVA-1 Tube Amplifier @ AmpsLab.com The caps you mention would be unlikely suspects. What sort of buzz is it? 100/120 Hz sawtooth? Both channels? __________________ If there's a sucker born every minute, where do the rest of them come from?

19th May 2010, 01:09 AM	#3
pix4work diyAudio Member Join Date: Sep 2009	http://www.diyaudio.com/forums/tubes-valves/167103-noisy-input-michaelson-austin-tva- It's higher than 120 Hz., maybe up around 400 Hz. and it's in both channels.

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24th September 2011, 09:24 AM	#4
apecg diyAudio Member Join Date: Jul 2010	Hi, Please check the grounding which is highly possibly the cause of the hum.

24th September 2011, 12:11 PM	#5
DF96 diyAudio Member Join Date: May 2007	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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