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Post subject: Blues Junior (made in mexico, cream board, 2003)
Posted: Mon Jun 24, 2019 10:42 am
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Hi All,

I am working on a Fender Blues Junior amp. Symptoms are low output volume and no reverb. Looks like the low volume is due to a bad input jack and the reverb was a bad connection inside the reverb tank. The reverb tank connector is a press fit thing. Anyone know where to get a better connector that will fit?

However, while looking around I see that the output tubes look like they have been really hot, markings almost burnt off and carbon inside the tube. R47 has gotten hot enough to scorch the PCB although it still reads OK and is running cool now. DC voltages look OK, but the AC voltage on D11/TP17 varies and goes up to 40VAC, seems like moving the ribbon cable affects the voltage. On D12/TP18 the voltage reads a consistent 3.5VAC. Any suspects for these readings? Obviously I need to remove the tube PCB and find the ribbon cable issues but is there anything else that is a likely culprit?

Thanks!


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Post subject: Re: Blues Junior (made in mexico, cream board, 2003)
Posted: Sun Jul 28, 2019 10:10 am
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Joined: Tue Feb 13, 2018 10:28 pm
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Location: SoCal, US
The BJ series tend to be biased very hot from the factory, and when re-tubed, the bias absolutely needs to be checked. Hot tubes and even red plating are common. Nearly every one of them can benefit from having the bias mellowed out. Obviously, it's going to impact the breakup/headroom.

Can you retrofit a pair of conventional RCA connectors to the reverb tank if not already equipped? My BJ is a 1st Gen Corona build and I'm pretty sure it already has RCA connectors.
If so, those have been in use since the birth of on-board reverb.

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