# 64' Vibroverb Custom re-issue



## SteveRayVaughan (Dec 18, 2010)

Hello, I was wondering if anyone could lend an opinion on my 64' RI Vibroverb Custom. I was looking around the filter caps and noticed there was a lead that was clipped (there's a 1/4" lead just hanging in mid air and it's obvious it was connect to R67 at some point). It goes from R80 to R67. I looked up the schematic and it confirms that there should be a lead connecting these two contacts.

Also, there should be a connection between R80 and R66 (confirmed again by the schematic which says "choke")

I was looking for problems as the power tranny gets very hot. I was wondering if these two (2) missing leads are a factor, and, if they should be connected regardless....

Many thanks!!

Any help would be great


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## stratele52 (Oct 25, 2010)

I can help you , where I can find this schematics ?


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## stratele52 (Oct 25, 2010)

Send us a picture of what you see inside


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## SteveRayVaughan (Dec 18, 2010)

Ok, here is the schematic: (it looks clear to me that R80 should connect to R67 - especially since there's an obvious clipped wire haging in that directio...and that R80 should also run to R66...now weather a lead runs off the filter board then comes back on somewhere else and connecting that way, I don't know)

Prowess Amplifiers - Fender - Schematics - Vibroverb Custom SRV DIAZ - 1964 Vibroverb custom with the Diaz SRV mods

How do I load up an image on here from my computer? (Just joined the forum 

Thanks
Dave


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## stratele52 (Oct 25, 2010)

Thank's for schematics, 

Yes, R80 must go to R 67, but not to R66. You have a section of filter caps disconnect , C40 and C33. The question is why they are not connectected ? Deffective capacitors C40 or C 33 ? Or someting else. ? 

I hope this help.

For load up an image , I know how, but as I'm french speaking I can't explain how to do.


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## SteveRayVaughan (Dec 18, 2010)

Ok here is a link to a pic...the red wire from R80 to R67 was put there by me...

Pictures by TheStevieRayVaughanExperience - Photobucket

Many Thanks


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## SteveRayVaughan (Dec 18, 2010)

Hello stratele52,

Thanks for the help. Which caps are C40 & C33? This amp has only been to one tech for one visit since being new and should all be stock / original factory condition....

Are you sure they are diconnected?

Also, why does the schematic have a line drawn on the board from R80 to R67 with the words "Choke"??

Thanks!
Dave


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## SteveRayVaughan (Dec 18, 2010)

Hello, latest update 

Yes C40 & C33 are connected for sure...also, I added a lead (Red wire) from R80 to R67 so it's now "Re-connected"...


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## stratele52 (Oct 25, 2010)

Also, why does the schematic have a line drawn on the board from R80 to R67 with the words "Choke"??---SteveRayV.
------------------------------------------------------------------------------------------------
This mean a choke is connect between the red wire and the orange wire. You can see that on the schematic. This is good.

So now everything is good. ?


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## SteveRayVaughan (Dec 18, 2010)

Well, thew reason i was poking around in the first place is the power tranny got really hot...too hot to touch....you could burn your finger leaving it on for 1 sec. Since re-connecting that wire...it still seems to be as hot. I've ruled out the tubes....it could have been biased a little too hot....70% is 44ma and one tube was at 45ma the other at 49ma...I've since matched them up at 43/44 ma...The possibility is the power tranny is bad....any thoughts??

Thanks!
Dave


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## greco (Jul 15, 2007)

SteveRayVaughan said:


> How do I load up an image on here from my computer? (Just joined the forum
> 
> Thanks
> Dave


You need to upload the pics from a host (e.g., photobucket)...then put the *copied photobucket link* in the space shown (after clicking on the icon that comes up when you reply/edit). It is the third icon from the right "Insert Image"...

Also, do you know if the tranny is original?...maybe it was replaced with one that is not the correct specs...just wondering

Cheers


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## Furtz (Nov 27, 2010)

If R68 and R80 weren't connected. you'd have no plate voltage on your preamp and inverter tubes, and your amp would be pretty much silent. Are they jumpered underneath the circuit board?
If the power transformer really seems too hot, you maybe should be looking at the power tubes or filter caps.


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## stratele52 (Oct 25, 2010)

You bias tubes at 45 and 49 ma, but how much 6L6's plate voltage you have now ? 

On schematic it is 455 volts, so the average bias is 40 ma . If you bias at 70% the voltage drop a bit and you can have more milliamps.

Have you the right speaker Impedance ( ohms) ?

It is normal that the power and output transformer comes hot after playing , You know that the Power transfo is the one at AC input and the Output transf is at the speaker/6L6's .

If you have the RIGHT bias ( or close) AND the RIGHT voltages AND the RIGHT speaker Impedance: Everything in your amp is OK and the heat from transformer are normal.
Did Fender put "cheap", too low power, transfos in this amp ?

I asume that you write is what it is in the amp AND you know how to mesure bias ( ma) ?


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## jb welder (Sep 14, 2010)

OK, so the amp has only been to one tech. since new and has otherwise been working fine. This means that wire was maybe put there to make it easier to measure something. 
If the connection you made had not been there the amp would not have been working so you must have duplicated a connection that was already there, probably under the board.
The schematic shows bias set for 38mA at about 455 plate volts (17.3 watts). You are biased a bit hot. If your line voltage is more than 120V you will have more than 455 volts on the plate so you would have to bring the bias down even more to get the stock setting of 17.3 watts.
Maybe this would make the PT run hotter but as someone else mentioned, it may well be normal. Try putting your finger on the PT of a similar amp to get an idea of how hot they run.


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## StevieMac (Mar 4, 2006)

AFAIK, your PT should never be runnung as hot as you've described it. I recall one of the techs here referring to a "rule of thumb" about holding your fingers on a PT for at least 5 seconds without major discomfort. Yours certainly sounds like it is not meeting that criteria. I haven't the foggiest idea what would could be causing that however, other than bias being WAY off...


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## WCGill (Mar 27, 2009)

Take it to a tech.


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## stratele52 (Oct 25, 2010)

WCGill, your amps are very nice, congratulation


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## WCGill (Mar 27, 2009)

Merci beaucoup!


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## stratele52 (Oct 25, 2010)

Dommage que tu demeures très loin de chez moi.


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## WCGill (Mar 27, 2009)

Votre Anglais est plus meilleur que ma Francaise. Tres loin?-pas de probleme. FedEx!


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