Moding a Fender Super Reverb back

[GermanyFelix]

Hey,
three day ago i got the Super Reverb. The first thing i thought was: "WOW" finally i got a Fender amp.. (Master Volume Silverface)

Price was 650$

he looks really nice i think, here are some pictures:










Well, the reverb is fine, and the Vibrato too. Very great sound. But i think it's more a typicall blues sound. I had a look at the tubes.

THEASE ARE EL34 ...

The seller did not care about that, because he used the amp to play metal.....he did not know somethign about the tubes :'(

Sounds like metal, when i do miserlou, it sounds like a slayer song. High gained.

So i want to mod the amp back to the 6l6

Does anybody know something of moding the amp back to 6L6 tubes? in which way should the bias changed? What resistors need to be changed? I will do some photos of the inside of the amp tomorrow.

Please help me!!!


Thx for help , Felix

[Steve A.]

... Does anybody know something of moding the amp back to 6L6 tubes? in which way should the bias changed? What resistors need to be changed? I will do some photos of the inside of the amp tomorrow...

You shouldn't have to reverse the mods done to the tube sockets. As for the bias setting, you can try adjusting the bias pot to see if you can set the bias voltage to -52v. You might as well pull the chassis and see how the bias pot is wired up. It probably came stock wired up as a hum balance control but I would guess that it was rewired as a bias adjustment pot when it was modded for EL34's. If there is a 4th terminal on the bias pot it would normally be disconnected during the mod and a 27k resistor to ground would be used for 6L6's. Look at the schematic for the AB763 Super Reverb for more details.

Good luck!

Steve Ahola

[GermanyFelix]

You shouldn't have to reverse the mods done to the tube sockets. As for the bias setting, you can try adjusting the bias pot to see if you can set the bias voltage to -52v. You might as well pull the chassis and see how the bias pot is wired up. It probably came stock wired up as a hum balance control but I would guess that it was rewired as a bias adjustment pot when it was modded for EL34's. If there is a 4th terminal on the bias pot it would normally be disconnected during the mod and a 27k resistor to ground would be used for 6L6's. Look at the schematic for the AB763 Super Reverb for more details.

Good luck!

Steve Ahola

Thank you for your help.

well at first i have to add that it is really hard to understand sentences in this topic because i'm from germany.

Tomorrow i will put some pics of the amp, i dont now where these resistors are i hope you will see it!!

thanks

[dodona]

a super has a blues sound, much unlike a twin. A super lets even a strat scream. However I don't think that the metal sound is the result of the el34. There must be another mod. Be aware of that.

[GermanyFelix]

i will do a video tomorrow

[Albert Kreuzer]

Inside pictures could be helpful, especially some close-ups of the power tube sockets and the bias circuit.

Cheers,
Albert

[GermanyFelix]

So, finally i got some pictures of the inside

i don't know anything about electrics but i think these white resistors are not original ones , are they?

installed tubes:

5U4GB

EL 34

El 34


RCA 7604 / 12AT7

RCA 7548 / 12AX7A

RCA 7404 / 7025

RCA 760? / 12AT7

Fender 7609 / 7025

Fender 7609 / 7025

[GermanyFelix]

[GermanyFelix]

[GermanyFelix]

http://www.youtube.com/watch?v=JGAdKehe5Tg video of the sound

[Albert Kreuzer]

Hi Felix,

those white "resistors" are electrolytic caps, and they are stock. The amp looks completely un-modified to me.
Probably you just need to stick some 6L6GCs in there - und fertig

Before changing tubes make sure that the bias voltage (pin 5 on the power tubes) is in the -50 to -55V range. If you "don't know about electrics", have someone check it for you who does...

IMO the best way to go is to give it to a tech for a cap job and a thorough inspection, new power tubes and proper biasing. Not a big deal.
Those EL34 did not harm the amp, but are biased way to cold and sure sound like

Cheers und gutes neues Jahr,
Albert

[Smitty]

Get Rid of the EL34s for now

I happen to love the sound of EL34s in a Super Reverb. However, you do have to modify the wiring of the output tube sockets in order to use them properly. From what I can see your amp has not been modified. In your case the EL34's suppresor grids are strapped to the control grid. It should sound pretty bad at this point. The factory bias on those amps is pretty cold. I'd bet you can safely change out the EL34s to 6Ls and enjoy a BIG improvement in tone.

[Rich]

The wiring looks original except for some of the wires related to the filter board. perhaps the filter caps were changed at one time.

It appears as the screen resisters on the power tubes are still 470 ohm.

The pot close to the bias board (with the pair of white caps) is an unmodified balance pot for equalizing the minus voltage going to the power tubes.

The pot in the back panel (between V2 and v3) is a hum balance pot hooked into the heater circuit. It replaces the 2 100ohm resisters (which go to ground from the 2 connections on the pilot light) used on some fenders as a center tap to eliminate hum from the heater circuit.

[Regis]

It's amazing this thing worked at all, or for any length of time with those el34s. From the transformer codes it looks like a 78?

Felix, this is what I would do:

• Install new 6L6 power tubes.
• Have the amp modded to Blackface specs by a good tech: Change the bias section to be adjustable, and remove that crappy master volume.
• Replace all electrolytic caps if it hasn't already been done.
• Not a bad idea to replace the 1.5k and 470 ohm resistors on the power tube sockets either.

There are mixed opinions about those dark blue caps, I would leave them in for now and see how the amp sounds after getting the 6L6's in.

This can be a great amp, with a few changes.

[stokes]

What Regis said.But by all means,if you dont "know anything about electrics",find a tech,it is dangerous to poke around an amp,there are potentially lethal voltages in there.