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Old 2nd May 2006, 05:00 AM   #1
jarthel is offline jarthel  Australia
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Default DIy tube-headphone amp (only 1 channel)

well it was been working fine in the past and suddenly, only the right channel has sound. I've change all the tubes so I somehow doubt that is the problem.

I measured the voltage across coupling out capacitor (470uF 350V in the schematic) and I'm getting +100V for the working right channel and +200V for the non-working left channel.

I am not really familiar with "debugging" circuits as this is not my area of expertise. Any help is appreciated.

Thank you very much for the replies.

ps.

I have attached the schematic.
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Old 2nd May 2006, 05:45 AM   #2
rpapps is offline rpapps  Antarctica
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Hi Jarthel
The 200 volts you have measured suggests that the lower half of V2 is not conducting. My first suspect would be R5. Have you compared the other voltage readings on the circuit?
Cheers
Rob
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Old 3rd May 2006, 12:37 PM   #3
kskr is offline kskr  Hong Kong
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Do all filaments light up?

Kenny
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Old 4th May 2006, 02:08 AM   #4
jarthel is offline jarthel  Australia
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Quote:
Originally posted by rpapps
Hi Jarthel
The 200 volts you have measured suggests that the lower half of V2 is not conducting. My first suspect would be R5. Have you compared the other voltage readings on the circuit?
Cheers
Rob
have not done so yet. will do this weekend.


Quote:
Originally posted by kskr
Do all filaments light up?

Kenny
yes. all the filaments light up as far as I can tell. I think there are 4 wires that light up.

Maybe it's not 4. But I'm sure all 3 tubes have the same no. of filaments that light up.


Thanks for the responses.
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Old 4th May 2006, 06:34 PM   #5
kskr is offline kskr  Hong Kong
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Hi Jarthel,
According to the schematic, you may want to check the V1 tube plate voltage first (right after the R2 where the schematic says "108V")

And check the voltage at bottom where the schematic says "2.5V"
also.

I'm not a pro but hope I could help anyway.

Kenny
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Old 5th May 2006, 04:23 PM   #6
Merlinb is offline Merlinb  United Kingdom
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Can you drop in an ECC82 orECC81 into that circuit?
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Old 13th May 2006, 01:34 PM   #7
jarthel is offline jarthel  Australia
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thank you all for the help.

I had the time to look at the problem closely yesterday and it seems the left channel ground wire got loosed. :|
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