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Post subject: Silverface Super Reverb
Posted: Sun Apr 24, 2011 5:04 am
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I was looking around at the Super Reverb on EBay (boy prices are kinda high, right now). Anyhow, found this SF one. It had this peculiar circuit. Running 2000 picofarad caps to ground from the 6L6GC cathode (which I kinda know about). But also 150-ohm, 7watt sandbox resistors. What was the purpose of those? To make the amp kinda fixed and cathode biased? Ohmage range doesn't seem correct. Anyhow, here the ad and the AB568 circuit that seemed to have those resistors.

EBay ad/photo:

http://i.ebayimg.com/00/$(KGrHqUOKkEE1w ... Dw~~_3.JPG

http://cgi.ebay.com/FENDER-SUPER-REVERB ... 0746045478


AB568 = resistors and ceramic caps:
http://www.ampwares.com/schematics/supe ... _ab568.pdf

AA1069 = resistors gone:
http://www.ampwares.com/schematics/supe ... aa1069.pdf


Thanks!


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Post subject: Re: Silverface Super Reverb
Posted: Sun Apr 24, 2011 6:44 am
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Posts: 292
All SF and BF Fender amps are way up in price. Have been for a while now. Tough to find a good deal. I have BF'd a couple of SR with that circuit with great results. As far as big wattage resistors. Had that in one of the 68/69s I BF'd. Didn't really care what they were trying to do because I was changing the bias/PI circuit to BF specs. Maybe ignorant of me but thats my lack of knowledge being exposed...:)
The thing that I dont like about that particular amp is that it looks like it has the real thin IPVC wiring. I am partial to the cloth covered stuff and the BF layout. (in the middle of a Bamndmaster Reverb to Vibroclone mod. I am replacing ALL the PVC wire and layout.)
Has the CTS alnicos which is nice....as long as they are in good shape.
Good luck with the auction


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Post subject: Re: Silverface Super Reverb
Posted: Sun Apr 24, 2011 7:26 am
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Yeah, those THIN white, rubber/plasitc coated wires are going to the heaters of each tube. This is NOT a good sign. I think the amp may have had PT troubles in the past. And I can only imagine what an NOS or new Mercury Mag PT costs for this amp.

And whoever the tech that fixed it, didn't even choose the proper color (green). Let alone cloth covered wires. The gauge seems awful small to be carrying amps of steady current. No?

http://i.ebayimg.com/00/$(KGrHqUOKkEE1w ... Dw~~_3.JPG


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Post subject: Re: Silverface Super Reverb
Posted: Sun Apr 24, 2011 8:44 am
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Well you got good news and bad news.The bad news is this is one of the early silverfaces that gave the SF a bad reputation for bad tone.Those capacitors on the tubes are what fender was trying to do with a fixed/cathode type of balance circuit.It sounds good in theory but in actuality it just sounds bad.You just clip them out and run a new wire to ground. As for the 2000pf caps the are for parasitic osculation you just clip them out they just kill some of the high end.

Well even more bad new. The amp is 41 years old it NEEDS new filter caps or a what we call a "Cap Job". They are the original from 69.

Now the good news.These amps are easy to work on and it all can be changed.But it will cost you.

I would Blackface this amp since it is a pretty common this to do on these amps.And would really not have much on the value of the amp.With the silverface circuit you can't bias the tubes you can just balance them.The point of that was so they could use unmatched power tubes. But we use nothing but matched tubes today. And it would involve fixing the phase inverter.

I would get this amp if you could get it cheap.I cost me about $100-150 in parts and i did this myself.If you have someone do it.It could cost about $500


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Post subject: Re: Silverface Super Reverb
Posted: Sun Apr 24, 2011 8:48 am
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BMW2002Ti wrote:
Yeah, those THIN white, rubber/plasitc coated wires are going to the heaters of each tube. This is NOT a good sign. I think the amp may have had PT troubles in the past. And I can only imagine what an NOS or new Mercury Mag PT costs for this amp.

And whoever the tech that fixed it, didn't even choose the proper color (green). Let alone cloth covered wires. The gauge seems awful small to be carrying amps of steady current. No?

http://i.ebayimg.com/00/$(KGrHqUOKkEE1w ... Dw~~_3.JPG

And to follow up on your second reply.Those amps didn't use cloth covered wire it was plastic covered and the guage shouldn't really matter it will only have 6.3 volts going through it.But i would consider changing it.


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Post subject: Re: Silverface Super Reverb
Posted: Sun Apr 24, 2011 9:19 am
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Joined: Thu Feb 21, 2008 12:52 pm
Posts: 292
joncarr1979 wrote:
BMW2002Ti wrote:
Yeah, those THIN white, rubber/plasitc coated wires are going to the heaters of each tube. This is NOT a good sign. I think the amp may have had PT troubles in the past. And I can only imagine what an NOS or new Mercury Mag PT costs for this amp.

And whoever the tech that fixed it, didn't even choose the proper color (green). Let alone cloth covered wires. The gauge seems awful small to be carrying amps of steady current. No?

http://i.ebayimg.com/00/$(KGrHqUOKkEE1w ... Dw~~_3.JPG

And to follow up on your second reply.Those amps didn't use cloth covered wire it was plastic covered and the guage shouldn't really matter it will only have 6.3 volts going through it.But i would consider changing it.


Yeah the thin wire looks worse than it is actually. Fender used two types of PVC covered wire. The "normal" stuff was a heavier looking. For a short time they used this IPVC stuff. The basis for a greeat amp is there. Its a good platform to build on and you will lern alot by getting it up to speed. Tons of info all over the net and not to mention the very expereinced guys on hits board (not including myself in that group....lol)

If you really want an SR....no need to rush into it. They are all over. BUT....trying to find a good deal.....thats the harder part...


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Post subject: Re: Silverface Super Reverb
Posted: Sun Apr 24, 2011 11:29 am
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Actually, I was taught that the current or amps carried through the wire is more important than the voltage. Or I should say, you can use a smaller gauge wire carrying 400 VDC, if it only carries 100mA RMS through it.

A heater line may only have 6.3VAC, but can carry more than 2 amps RMS to heat the power tubes and gain stage/PI tubes. You'll notice that the thickest wire used in most amps is the heater line. And some amps use 6.3volt rectifiers, so they may need to be heated by the same line that heats the other tubes. So more current demand.

At least that's how I learned the thing...

I'll keep looking for that SR. Really would like a BF... like my old one. :D

Happy Easter, all!


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Post subject: Re: Silverface Super Reverb
Posted: Sun Apr 24, 2011 12:07 pm
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joncarr1979 wrote:
Well you got good news and bad news.The bad news is this is one of the early silverfaces that gave the SF a bad reputation for bad tone.Those capacitors on the tubes are what fender was trying to do with a fixed/cathode type of balance circuit.It sounds good in theory but in actuality it just sounds bad.You just clip them out and run a new wire to ground. As for the 2000pf caps the are for parasitic osculation you just clip them out they just kill some of the high end.


+1

That AB568 layout was about the saddest excuse for a circuit revision in Fender's history. And most of that "parasitic oscillation" that Jon referred to wasn't even audible when the amp was driven into clipping. The CBS engineers who dreamed that "fix" up should've stuck to building record players and clock radios!

Arjay

_________________
"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: Silverface Super Reverb
Posted: Sat Mar 09, 2013 12:44 pm
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Roadie
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Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
joncarr1979 wrote:
Well you got good news and bad news.The bad news is this is one of the early silverfaces that gave the SF a bad reputation for bad tone.Those capacitors on the tubes are what fender was trying to do with a fixed/cathode type of balance circuit.It sounds good in theory but in actuality it just sounds bad.You just clip them out and run a new wire to ground. As for the 2000pf caps the are for parasitic osculation you just clip them out they just kill some of the high end.

Well even more bad new. The amp is 41 years old it NEEDS new filter caps or a what we call a "Cap Job". They are the original from 69.

Now the good news.These amps are easy to work on and it all can be changed.But it will cost you.

I would Blackface this amp since it is a pretty common this to do on these amps.And would really not have much on the value of the amp.With the silverface circuit you can't bias the tubes you can just balance them.The point of that was so they could use unmatched power tubes. But we use nothing but matched tubes today. And it would involve fixing the phase inverter.

I would get this amp if you could get it cheap.I cost me about $100-150 in parts and i did this myself.If you have someone do it.It could cost about $500


I have a 72' Super Reverb-totally original. It still sounds great. The only thing I've changed is the tubes. IMO, blackfacing amps ruins them. The only reason I would change a part is if it was broken. If you want a blackfaced amp, buy one. I've bought several early silverface Fender amps that were modded and got them cheap because the owner no longer liked the sound. I restore them to spec with high quality parts and they sound wonderful.


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