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Post subject: BJ Sounds Like a Distortion Pedal - And No Output.
Posted: Mon Feb 27, 2017 2:42 pm
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So I just fixed by Black blues Jr recently (thank you to all the guys here) my cousin has the same amp BUT IN TWEED, same circuit. We've changed all the tubes (because they were about 5 years old).

We thought they would remedy the problem he is having. The amp sounds like there's a FULLY CRANKED DISTORTION PEDAL in front of it.

Im not talking about tone that comes from a bad screen grid (where it's a little wooly) but full on distortion with NO VOLUME, as if its on volume number 2 or so.

I've checked that its getting proper voltage and it is but my question is do OP AMPS cause these issues? Not sure at all, but if there are any guys with input here that would be helpful and I'd luv ya for ever :P


Thanks


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Post subject: Re: BJ Sounds Like a Distortion Pedal - And No Output.
Posted: Mon Feb 27, 2017 9:56 pm
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You have access to a tube tester? Sounds like one or more of the tubes are dying.


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Post subject: Re: BJ Sounds Like a Distortion Pedal - And No Output.
Posted: Mon Feb 27, 2017 11:32 pm
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We changed them all to new ones.


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Post subject: Re: BJ Sounds Like a Distortion Pedal - And No Output.
Posted: Tue Feb 28, 2017 12:52 am
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If the output tube idle bias is ok... sounds like leaky coupling caps. Measure the DC voltage on the grid side of each coupling cap. More than 1VDC ---> change cap.

All voltages on the anode plates of input, gain, phase inverter are within specs? Disabling all EFX switches does not change the distortion problem? Try another guitar? Patch cord? Eliminated all pedals from the chain?


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Post subject: Re: BJ Sounds Like a Distortion Pedal - And No Output.
Posted: Tue Feb 28, 2017 2:17 am
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Ryan41018 wrote:
We changed them all to new ones.


If you don't put brand new tube and use tubes tester to find good tubes, Many tubes tester are not reliable.

Distortion ; Phase inverter circuit ; check resistors.
Output transfomer; blow
Power Supply voltage wrong


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Post subject: Re: BJ Sounds Like a Distortion Pedal - And No Output.
Posted: Wed Mar 01, 2017 12:08 am
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We did install new phase inverter (V3) but still the same ??


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Post subject: Re: BJ Sounds Like a Distortion Pedal - And No Output.
Posted: Wed Mar 01, 2017 2:58 am
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Ryan41018 wrote:
We did install new phase inverter (V3) but still the same ??


Phase Inverter circuit is not only a tube, it is resistors, capacitors......

Please read my first answer.


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Post subject: Re: BJ Sounds Like a Distortion Pedal - And Lo Output. SOLVE
Posted: Thu Mar 30, 2017 11:42 am
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Finally had time to get into this amp. SUPER DUMB SIMPLE

Bad R35 & R36

Rock on!


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