69 Super Reverb Resto ?'s

[1bmf]

So I'm finally getting around to getting my 69 SR serviced but I have a few questions first. I'm going to have my amp tech convert the amp to BF specs but he has never done that before so I'm hoping you guys could point me to either a kit or just a step by step how-to that I can give to the tech. My second question is about the rectifier tube. The one in the amp is at least 25 years old and no longer has any markings on it to identify it. What are some good replacement rectifier tubes for the amp? As always thanks in advance for the help.

Matt

[Cygnus X1]

Rectifiers last just about forever.
I still have the original Telefunken GZ34 in a '67 Deluxe Reverb.
You shouldn't need to replace it.

I'd be a little wary of having the amp blackfaced by someone who hasn't done it before. My opinion...

[ziess]

If it's the original 5AR4 then I'd leave it unless it's giving you problems. It may have a 5U4GB... Not sure when they started using them. If you want it truly blackfaced you'll want to make sure it's running a GZ34/5AR4.

You tech really ought to be able to do this... Whether he's done it or not it's not an especially complex procedure. All he has to do is rearrange some parts to make it look like the classic blackface AB763 circuit. Simple.

Tommy.

[1bmf]

Thanks for the replies. I should have mentioned that while my tech hasn't done a SF->BF conversion that he can remember, he is a very good tech with 30+ years of restoring vintage amps. I just wanted to make it easier for him with some step by step directions.

Matt

[ziess]

He shouldn't have any problem working it out, seriously. It's not a hard thing really.

Y'know if yours is a '69 then it's entirely possible that it's essentially a blackface on the inside.
Got any gut shots?

Tommy.

[phantomman]

If it's a verifiable '69 then chances are it's an AA1069 circuit -- which is significantly more desireable than the AB568, which it replaced. It's also easier to back-date from a 1069 to a 763, requiring only a handful of parts an' a few minutes with a soldering pencil.

HTH

[steve25]

Some notes on blackface tone/B+ voltage.
The AB763( classic BF SR) uses a PT woth a part number 125PSD, with a voltage of 360 feeding its 5AR4 recto.
The AB568 amp uses the same PT with 365 volts hitting a 5U4 recto.
The AB1069 model uses the same PT with 375! volts hitting its 5U4 recto, so something is amuck somewhere!
the 5U4 rectos will pull1 amp more heater current then the 5AR4 recto, so could this be why so many silverface SR have come down with burnt up PT problems? I think the new penny counter at Fender/CBS wanted to use the more plentyfulll/cheaper 5U4 recto in the SR.
I would love for someome who has one of these amps to measure the change in heater voltage when using a 5AR4 and a 5U4GB recto.
My guess is that the heater voltage will drop with the added 1 amp of current tha the PT is being called apon to put for the 5U4GB recto, The difference form a heater voltage of 6.5 or 6.3 volts down to 6.1 volts will make for a big difference in preamp gain, followed by the fact that the 5AR4 recto will drop about 15 to 20 less volts DC than the 5U4GB recto.
These two facts may have more of a effect on the amp having a blackface tone and responce than the silverface PI circuit changes , other than if you have a amp with the anti-oscilation caps on the output tubes.
And also you have to mention the fact that the soft startup of the 5AR4 will make for longer tube a filter cap life!
So anyone here have a SILVERFACE SR and these two rectos to post the voltage changes in heater and B+ levels?

[phantomman]

Interesting, Steve.

In late '67 I bought my first new Fender amp -- a SF drip-edge Super Reverb, with a build date of some time in August. The rectifier tube (installed on the chassis, specified in the schematic, and shown on the tube chart) was a GZ34.

[steve25]

Yup! thats just the euro version/number for a 5AR4.

[1bmf]

Here are some gut shots. Also the serial number is A 41335.

Matt

[wingnut1]

Here are some gut shots. Also the serial number is A 41335.

Matt

Hey Matt, great shots of your super. I was wondering if I could trouble you for a more strait on shot of the wiring on the RCA jacks. Shooting them from above makes it more difficult to see the connections.

Thanks,

Steve.

[1bmf]

Sure, I'll try to get some more shots in the next couple of days.

Matt

[wingnut1]

Sure, I'll try to get some more shots in the next couple of days.

Matt

Thanks again.

[CJ Neel]

I would forget about BF'ing it, put in fresh power supply, cathode bypass, and bias electrolytics and enjoy your amp. If those OD's are 225ps, the I'd leave 'em. Otherwise, I go with Mallory 150's.

[1bmf]

I would forget about BF'ing it, put in fresh power supply, cathode bypass, and bias electrolytics and enjoy your amp. If those OD's are 225ps, the I'd leave 'em. Otherwise, I go with Mallory 150's.

Could you further explain what all the things you said to replace are? I'm new to amp restoration. Thanks.

Matt

[CJ Neel]

Electrolytics. The big caps under the doghouse. Cathode bypass caps are on the board. They're the white ones in your photo. Bias cap is in the upper left hand corner looking from the bacl of the amp.

[Kap'n]

I would forget about BF'ing it

I dunno Chris - from the big cement resistors by the power tubes, it looks like he's got the AB568 circuit.

http://www.ampwares.com/schematics/s...b568_schem.pdf

Some people like 'em, but I suspect he'd like it better with a few tweaks.

[steve25]

Yup, thats the dredded partly cathode biased output stage all right!That craps gotta go!
Also what that small terminal strip and added resistors up by the bias pot?
Hey wingnut 1, if you need to see a good picture of the wiring layout, go to the fender amp field guide site, and click on the listing for schematics/layouts, then scrol down to the super reverb listings and click on what you want to see, it will be far better than a photo!

[wingnut1]

I have a good layout, what I want is pictures of how Fender actually wired grounds and things like that. I've never seen a good picture of this part of an original BF amp and I thought that it might help.

[steve25]

the fender way of grounding is not the best anyway, as they land the ground for the 6l6 screen filter with all the other preamp grounds when it should land with the ground for the PT center tap.
Basicly all the grounds from the grid side of the PI back thru the whole preamp including PS filters should be star grounded back to the input jack, and all the other grounds from the plate side of the PI tube should be grounded with that PT center tap ground.

[Kap'n]

the fender way of grounding is not the best anyway, as they land the ground for the 6l6 screen filter with all the other preamp grounds when it should land with the ground for the PT center tap.

But yet I've never had an issue with a Fender. It might make a difference with a higher gain amp, but stock Fenders have always been quiet enough for me.

[CJ Neel]

But yet I've never had an issue with a Fender. It might make a difference with a higher gain amp, but stock Fenders have always been quiet enough for me.

Ditto.

[wingnut1]

From the pictures I'm seeing something different on the RCA jacks for the Reverb and Reverb Transformer than I visualized when wiring mine so I wanted to get a clearer view.

[1bmf]

Here are more pictures. I took a bunch more shots of all the jacks since they couldn't be seen very well from the earlier pictures. These shots didn't turn out as well as I would have liked so feel free to ask for more pictures. In regards to if I should BF or not, I'm the type of person who is never completely happy with my sound. Even if I loved the sound of the amp as it is, I will always wonder how much better I might like the amp if it was BF'ed. I'm pretty sure it's a disease, but I would bet some of you share the same illness.

Matt

[wingnut1]

Thanks for the additional pictures Matt, that helps.

[steve25]

the grounding schem does make a difference On the latter amps where they started to get real sloppy with the wiring layout and had oscilation problems. If only they kept to the earlyer neet wiring layout they may never of had to stick in those high end tone sucking ceraimic caps on the output tubes!
Ah! but I guess its faster to pay for and wire in 2 cheap caps than pay for the labor of someones neat wiring time !

[1bmf]

Hey, here are a couple links to some SF->BF guides I was hoping you guys could look over and let me know if they look right.

http://www.schematicheaven.com/mods/silver2blackmod.htm

http://blueguitar.org/new/schem/fend...-sf_bf_mod.pdf

Here is a link to a kit that comes with instructions. Is it worth the money?

http://kendrick-amplifiers.com/Merch...gory_Code=0802

Thanks,
Matt

[1bmf]

Bump before the amp goes in the shop

[Kap'n]

Just say no to Gerald Weber.

[1bmf]

K, thanks