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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 11:11 am
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Yes I did, played amp for 10 mins.


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 12:25 pm
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Check the idle bias of the 6L6GC tubes. Should be steady readings around 40mV (with bias adapter).

If you have access to a DVM and can safely run the amp on a bench --- check the bias voltage supply. I don't know if you have a BF or SF Pro Reverb. Amp on (watch out for high voltage in circuit). Speakers connected. No guitars plugged in. Volume, Reverb, Vibrato controls at zero.

For AA165 BF the bias voltage should be -51VDC (with pot and half-way point). Measure at the junction of the two 220k-ohm grid-to-ground resistors.

http://ampwares.com/schematics/pro_reverb_aa165.pdf

For the AA1069 SF the bias voltage should be -44VDC at negative side of the bias cap.

http://ampwares.com/schematics/pro_reverb_aa1069.pdf

You did solder the new bias supply filter cap with the (+) end going to the ground (chassis)? Positive on left side, facing rear-to-front, upside-down --- see my photo on last page.


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 3:09 pm
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Yes old cap was removed and during testing all was fine, bias was solid.


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 7:32 pm
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Try contact cleaner on the 6L6GC tube sockets. Do the tubes feel loose when they are in the sockets? May need tightening.

Use proper Slo-Blow 2 amp fuse.

Keep us posted!


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 9:09 pm
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Cleaned sockets, retentioned female socket pins before I replaced bias cap.

Update, I pulled rectifier tube, replaced 2 amp fuse, turned on power (no fuse blow) took it off standby to power up and NO FUSE BLOW. Bad rectifier tube????


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 10:40 pm
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Do you have another GZ34 or 5U4GB you can try in the amp?


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 11:17 pm
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I have 5u4gb in my Mesa, is it safe?


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 11:26 pm
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Perfectly fine. See if fuse blows. If not -- the original rectifier is bad. I do have some US 5AR4 and a few Philips-Mullard GZ34, if you are interested.

If the fuse still blows --- prolly the PSU caps under the doghouse.


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 11:32 pm
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I will try the 5u4gb. Caps in dog house changed last Friday. I found they were from 1966 year.

Also yesterday I couldn't go higher than 22ma on the bias pot with my Tube Dr. Bias master probe??


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Tue Aug 09, 2016 11:51 pm
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Hmm... low bias point usually means tired output tubes. But, since these are brand new 6L6GCs --- there maybe something still amiss with the bias power supply.

Are you able to take photos of the circuit? Esp near the power transformer side of the circuit board. And the 6L6GC sockets?

Kinda like this photo:

ImageThanks!


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Wed Aug 10, 2016 8:15 am
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Image

Image

Image

Image


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Wed Aug 10, 2016 10:16 am
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Thanks, for photos! :)

Looks like most components are original (this is good). I need to see just a bit more of the bottom portion, below the bias pot (on top photo). And both 6L6GC sockets. Sorry... this will help determine circuit type and if resistors on sockets look ok (screen & grid stoppers).

Looks like an aftermarket power tranny. Did the original one die?

Were you able to try the 5U4GB rectifier?


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Wed Aug 10, 2016 3:25 pm
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Image
Image[/[URL=http://s7.photobucket.com/user/69targa912/media/IMG_2749_zpsvhwdffaz.jpg.html]ImageURL=http://s7.photobucket.com/user/69targa912/media/IMG_2750_zpsbhwvj3wg.jpg.html]
[Image]http://i7.photobucket.com/albums/y286/69targa912/IMG_2750_zpsbhwvj3wg.jpg[/IMG][/URL]]Image



BMW - I made one of those limiter light bulb (Rob Robinette) on the internet gives instructions.


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Post subject: Re: Pro Reverb (pulling my hair out!)
Posted: Wed Aug 10, 2016 3:44 pm
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That flyback diode in the bias supply looks a little crispy......

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: Pro Reverb (pulling my hair out!)
Posted: Wed Aug 10, 2016 4:06 pm
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Diode does, but it tests normal??


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