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Post subject: Noisy bluse jr amo
Posted: Fri Aug 17, 2012 1:00 pm
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Hi,

my blues jr amp is producing annoying humm noise even when the master and volume are at 0 and the input cable is unplugged.
anyone knows what can be the problem with it?

thanks


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Post subject: Re: Noisy bluse jr amo
Posted: Fri Aug 17, 2012 4:45 pm
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Hi gilye,

From the limited info, I would suspect the PI tube (V3) or output tube.

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Post subject: Re: Noisy bluse jr amo
Posted: Fri Aug 17, 2012 11:26 pm
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Thanks for the response.

I am not sure I know which are the V3 tube and the output tube.
Can you please point me to thier position?

Thanks


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Post subject: Re: Noisy bluse jr amo
Posted: Sat Aug 18, 2012 5:26 am
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Looking at the back of the amp, starting at the right counting to the left. V1, V2, V3 are the smaller tubes, V4, V5 are the larger tubes. V1 and V2 are preamp, V3 is the PI (phase inverter), V4 and V5 are output.

You can use one known-good 12AX7 (or similar) to substitute in positions V1, V2, V3, one at a time. The output tubes should be replaced as a matched pair. It's a good idea to check the bias when replacing output tubes, and it might be necessary to use low current draw output tubes as the stock BJr has no bias adjustment pot.

More great info about the BJr:
http://billmaudio.com/wp/?page_id=2

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Noisy bluse jr amo
Posted: Sat Aug 18, 2012 9:02 am
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shimmilou wrote:
Looking at the back of the amp, starting at the right counting to the left. V1, V2, V3 are the smaller tubes, V4, V5 are the larger tubes. V1 and V2 are preamp, V3 is the PI (phase inverter), V4 and V5 are output.

You can use one known-good 12AX7 (or similar) to substitute in positions V1, V2, V3, one at a time. The output tubes should be replaced as a matched pair. It's a good idea to check the bias when replacing output tubes, and it might be necessary to use low current draw output tubes as the stock BJr has no bias adjustment pot.


More great info about the BJr:
http://billmaudio.com/wp/?page_id=2


+1 on BillM's site!

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Post subject: Re: Noisy bluse jr amo
Posted: Sat Aug 18, 2012 10:53 am
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Thanks!!!


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