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Post subject: Re: Super Reverb - Redplating like crazy, no -52vDC bias
Posted: Fri May 17, 2013 2:23 am
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Location: Province de Québec, Canada
taskerc wrote:
Also checked bias pot again and it seems fine as does the 27K resistor to ground.

Now putting it all back right I am getting -47VDC at junction of 220K resistors :-( Confused.

Tonight I am now tired so I will take another look tomorrow to confirm and maybe test again with power tubes.

Chris


So everything look good ? Dont forget to check -47 VDC at tubes pin BEFORE put tubes in their socket . Give some tension to pins to be sure of good contacts .

Chance it is a bad solder you reheat with your test. Look carefully id a wire is not half brken in bias circuit . Rehat all solder too.


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Post subject: Re: Super Reverb - Redplating like crazy, no -52vDC bias
Posted: Fri May 17, 2013 6:01 pm
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OK - I think I found the issue.

I forgot that I also replaced the original SIlverface control panel with a Blackface version. When trying to get the lampholder loose to make the swap it looks like I messed up and disconnected the 470 ohm bias resistor by mistake (force?).

So when I reconnected it, that is how I think I got voltages back - it occurred to me this morning that when I followed Louis' instructions, I had not disconnected the 470 Ohm resistor but I noticed it was disconnected and re-soldered.

So right now the amp is again working, The old tubes are functional but my bias probe told me there was a substantial bias voltage difference between the tubes. So I think I probably damaged one of them at least a bit and will now get a new matched set.

So the moral of the story for me is twofold:

1) stop messing around with this amp and just play it
2) if I cannot avoid 1) above, be far more careful and take pictures

Thanks again for the support Louis and Arjay - I really appreciate it!

Chris


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Post subject: Re: Super Reverb - Redplating like crazy, no -52vDC bias
Posted: Fri May 17, 2013 6:59 pm
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The vintage amp tech's creed is the same as that of a physician......

"First, do no harm."

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Super Reverb - Redplating like crazy, no -52vDC bias
Posted: Fri May 17, 2013 8:07 pm
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Retroverbial wrote:
The vintage amp tech's creed is the same as that of a physician......

"First, do no harm."

Arjay


+1 fer sure


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Post subject: Re: Super Reverb - Redplating like crazy, no -52vDC bias
Posted: Sat May 18, 2013 1:17 am
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taskerc wrote:

So the moral of the story for me is twofold:

1) stop messing around with this amp and just play it
2) if I cannot avoid 1) above, be far more careful and take pictures

Thanks again for the support Louis and Arjay - I really appreciate it!

Chris

You are welcome .

Fo me the moral is ; if you do any king of work BEFORE problem , check what and where you do some work.


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Post subject: Re: Super Reverb - Redplating like crazy, no -52vDC bias
Posted: Sat May 18, 2013 7:00 pm
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stratele52 wrote:
taskerc wrote:

So the moral of the story for me is twofold:

1) stop messing around with this amp and just play it
2) if I cannot avoid 1) above, be far more careful and take pictures

Thanks again for the support Louis and Arjay - I really appreciate it!

Chris

You are welcome .

Fo me the moral is ; if you do any king of work BEFORE problem , check what and where you do some work.

Wise words :-)

Thanks.


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