Fender 400 PS, now on the bench. Know anything about this?

[Matthews Guitars]

I'm starting to think that maybe it's just better to skip the reverb circuit entirely. The deeper I get into the amp, the more I'm seeing that is at variance with the standard 400PS type.

My friend who took this on undertook a project of re-engineering it. And abandoned it for at least 10 to 15 years, then died.

So he's no help. Darn it.

I think some tubes are reassigned to different functions.

Definitely he changed around things even in the power supply. The big ceramic bathtub resistor that should be on the OT side of the chassis bolted to a board on the side wall, along with its entire circuit, has been moved to the PT side of the chassis instead. And actually that makes sense. The wiring in this area has been simplified.

Here's a pic of the five preamp tubes and the board. Try to compare it to an unmolested original and you soon lose count of the changes.

And another pic of the same area of an unmolested original.

I'll admit, tracing out and redrawing schematics has never been my strong suit. Oh boy.

[martin manning]

Have you tried to find Fender factory documentation for this thing? Maybe inquire here: https://www.talkbass.com/threads/offici ... ub.481860/

edit: I see you have been over there already. No luck then, eh?

[Matthews Guitars]

I've had limited success with finding information but I've come to the conclusion that this amp has been "re-engineered" without documentation available.
It's one of a kind. Stock model documentation will be of limited usefulness.

So I'm going to have to trace out the function of each half of each preamp tube and see how they have been reassigned. And then start sorting it out THE HARD WAY.

There will be no quick fixes with this. It's going to require brain power and time.

[martin manning]

Stock model documentation will be of limited usefulness.

I was thinking more towards a restoration activity, or at least to understand what has been changed from the original design.

[Matthews Guitars]

Other than reverb it's a running amp and the relocation of the inrush limiter resistor and related circuitry actually makes sense. The original parts are gone and my only intent is to get reverb running. I'm not interested in reverting it to its stock configuration given the hassles involved in figuring out what that would entail.

There are probably about two dozen of these amps in existence, at a guess. What little sales information I can find suggests only about 50 to 60 were ever made, and it's fair to assume that at this point half of them are gone.

There are parts in it that I literally can not identify. Like that flat rectangular ceramic package that seems to be a 3 legged capacitor. On mine I had to do some surgery to repair it as it had two broken legs. By being CAREFUL and CREATIVE I fixed it. If it had not been repairable, I don't even know what would be a functional substitute for it. I sure don't know where to find a replacement for that part.

[GAStan]

There are parts in it that I literally can not identify. Like that flat rectangular ceramic package that seems to be a 3 legged capacitor. On mine I had to do some surgery to repair it as it had two broken legs. By being CAREFUL and CREATIVE I fixed it. If it had not been repairable, I don't even know what would be a functional substitute for it. I sure don't know where to find a replacement for that part.

You've piqued my curiosity and I like a challenge. If you can post a pic of this part making sure any numbers etc are legible I'll see what I can find on it.

[Matthews Guitars]

If there are identifying numbers on that part they're on the downward facing side of it and I'm NOT going to risk moving it. \
But here's a photo of it. Maybe I can find another photo of it from photos of other examples of this amp.

[martin manning]

This thing. More than likely a multi-component package, typically R's and C's.

[sluckey]

Other than reverb it's a running amp.... and my only intent is to get reverb running.

The reverb circuit is 99% identical to any AB763 reverb circuit. Same reverb transformer and tank. Should be straightforward troubleshooting and repair.

[martin manning]

I've had limited success with finding information but I've come to the conclusion that this amp has been "re-engineered" without documentation available.
It's one of a kind. Stock model documentation will be of limited usefulness.

So I'm going to have to trace out the function of each half of each preamp tube and see how they have been reassigned. And then start sorting it out THE HARD WAY.

There will be no quick fixes with this. It's going to require brain power and time.

FWIW, in The Soul of Tone there is a bit about the 400PS, and it says Rich Koerner (the guy who provided he info on the Time Electronics web pages) obtained factory documentation from personal communication with designer Ed Jahns. He started an owner's club, and found over 100 people (world-wide) that have them.

[GAStan]

This thing. More than likely a multi-component package, typically R's and C's.

Found another Fender amp schematic that uses it, top middle of the schematic. Found this with the "064592" part number. Number on the components also agree "113C12", but found a reference to it as "113011".

Might be able to get one from an authorized Fender repair shop should you ever need one.

Still haven't found out what it is...

[GAStan]

This thing. More than likely a multi-component package, typically R's and C's.

Found another Fender amp schematic that uses it, top middle of the schematic. Found this with the "064592" part number. Number on the components also agree "113C12", but found a reference to it as "113011".

Might be able to get one from an authorized Fender repair shop should you ever need one.

Still haven't found out what it is...

Forgot to attach file.

A photo of the device itself might help, especially if it has additional markings.

[GAStan]

Sorry, I see you already posted a pic. Initially I only saw Martin's post and missed yours.

[Stevem]

Indeed it’s a r& c package like Martin said.
Ampeg was famous for using such since the mid 60s all the way into the V4 and V9 era amps .

Also I don’t think any of these amps out of all of however many where made have bit the dust and been tossed unless both the PT and OT where toast.

Such would be nuts since there so rare!

[Matthews Guitars]

Saying it's an "R&T C package" tells me exactly nothing. Like "Oh, that's a left-handed retwizzlated garfledob."

Do you have any other information to offer about this device, its manufacture, its type, or function, to give me some context?