Holy Hell! Fender Super Amp. Mid 90's.

[eddie25]

I'm speaking of the Pro-Tube series, sometimes also called the Concert I think. Says "Super Amp" on the front though.

I got one of these to check out and I gotta say this may be one of the least serviceable amps I've ever seen. The power tubes were shot, so I loaded some others in and they seemed to do the trick except one was red-plating slightly. So time to open it up and to my surprise it's one giant circuit board, upside down. No bias pot, no resistor numbers or any parts that you can get to. There's also a piece of foam GLUED over part of the board.

So now I find the schematic,

http://web.archive.org/web/200807170341 ... er_amp.pdf

You can see around the bias circuit it says "optional bias circuit." WTF? So, this thing likely doesn't even have a bias pot? Not sure, but I'd like to find out. (hint: it's not under the foam)

So now I'm thinking ok, flip the board and see if at least I can locate the resistors I need to change to get it biased up (looks like R158), and maybe check out the screen resistors just in case.

Not so fast! Some of the tube sockets are soldered to the board, some are attached at the chassis with wires running to the board, footswitch and effects jacks are all attached to the board. Total pain in the ass, but I'm still trying. I take out any screws, undo a few sockets from the chassis, undo the jacks...

It still won't turn over, it's loose, but there's no way I could get to the board. it's got ribbon cables going to the pot board, short wires, and not enough space.

Anyone else ever conquered one of the cluster-fucks? I just can't see why you would ever make an amp that was so difficult to bias, change screen resistors, or change caps for that matter. Hopefully I am missing something here... I'd love to get this thing in top shape. As of now it seems pretty worthless.

[David Root]

I don't envy you. Closest I came to that was a R.I. 65 Deluxe.

That schematic looks like it was designed by someone who knew nothing about how MI amps work, didn't understand tubes and was not a musician either. And the final design as built was approved by a committee of accountants and non-musical MBAs.

[Andy Le Blanc]

green vault... oh boy

The time is in the dis-assembly and reassembly

WATCH OUT------ go easy removing the knobs, its very easy the frig up the pots.
The shaft will pull right out of the pot, you must pull the knobs to get out the board.

WATCH OUT------ its east to break any wire leads, go easy with the board.

WATCH OUT------you have to remove the socket and tube clip screws, and a
few more across the chassis, dont loose em.

WATCH OUT------ theres one of the push it strain reliefs on the verb cord.
you have to get it out to get slack to move the board.

All in all just go slow

Get the schematic and layout and check it out from the pin out on the tube sockets
You can take voltages of the tube circuit before you commit.
every tube amp is the same irregardless of any thing else, the meter can tell you a lot.

If/when you find say a bad resistor, or say its one without the optional adjustable bias,
remove the part, de-solder pretty well, then you can replace form the other side
of the green wall, so you can get after it, after its reassembled,
double check chassis clearances with larger parts like caps.

It goes back together in the reverse order that you took it apart , be patient.

And I nearly forgot all the pot and jack nutz/washers...you really got to
hold your mouth right just to get it apart and you cant test until after you
get it back together.

Dont be afraid to pay a bench fee, it is a major pain in the arse.

[eddie25]

ARG! Thanks Andy!

I'll check the screen resistors from the top of the board. Only one 5881 tube was out originally, and the opposite side was glowing with the new set, so that has me a little worried, I hope the OT is OK. I wish I could even see the OT wires!

I couldn't seem to find a layout for this particular amp either.

The green vault... I like that, it's the truth. Another reason to buy hand wired amps.

[PCollen]

I'm speaking of the Pro-Tube series, sometimes also called the Concert I think. Says "Super Amp" on the front though.

(snip) .

I can empathize with you. I bought a discounted Fender Prosonic from GC in 1999 (after the party, BTW) , took it home and opened it up. I realized that the PCB had been replaced and the flying leads looked like a worm's-nest..the horror, the HORROR. I took it back the next day...didn't even play through it.