Fender Bassman 135, need layout diagrams/photos

[Matthews Guitars]

I'm starting to rebuild a partially disassembled Bassman 135 that was partially taken apart by a friend of mine, who was going to modify it,
but he died before the job was done and I "inherited" the amp. I want to rebuild it to stock specs FIRST before I make any decision as to what to do with it.

If anybody here can point me to some layout diagrams or photos of the internals of one of these amps that would be helpful in rebuilding it, I'd really appreciate it.

I did find a few good clear photos but they're of a different variant than mine. Even the eyelet board is slightly different. So it's useful but only to a point.

I'd also like to get a shot of the insides of the capacitor bank. I know the cap values I need, but it looks like this amp has been rewired for a different capacitor layout
than stock, so I want to revert it to stock as well.

I do have the schematic, and could certainly get the amp running from that alone, but as I'm trying to rebuild the amp as Fender built it, the diagrams and photos
would still be very much appreciated.

Once I've got it running, THEN I can start thinking about the possibilities of modifying it. There's plenty of room inside for some modifications.

[chief mushroom cloud]

try here
https://el34world.com/Forum/index.php?t ... #msg255442

[Stevem]

Don’t take this the wrong way as I don’t know what your skill set level is, but if you need to build by photos ( especially with something as easy as the filter cap section) and not by using a schematic then your in over your head I have to say!

If you screw up you could take out one or two ( power or output) very expensive to replace transformers , or about 100 bucks or so in output tubes and then your likely shelving the project.

Please post up a lot of good photos / gut shots of what you are dealing with so we can get a far better feel of where you really stand with this.

Thanks in advance!

[Ten Over]

This may be of use. WHT 1 and WHT 2 can be deleted.

[Ten Over]

Alternate schematic

[Matthews Guitars]

I CAN build purely from the schematic. I've only got about 35 years of experience as an electronic technician, and I've worked on every kind of equipment you can imagine. Audio, video, radio, avionics, medical, test and measurement, pretty much every category there is.

But in this case I want to rebuild the amp to its stock configuration. And as it turns out, there is more than one revision of the Bassman 135 and as luck would have it, apparently all documentation and photos I've got for it are for a different version than mine.

It doesn't help that the work that was already done to it is also not for its stock configuration. My friend clearly had something different in mind, but I've found no documentation on what he was planning. I'm almost going to have to strip it back to a bare chassis to revert it back to the stock circuit anyway.

I noticed quickly that this amp doesn't have a choke. I'm contemplating adding one. And if I decide to go with a conventional output transformer rather than the stock ultralinear transformer, as luck would have it I do have a good spare Bassman 100 OT.

[Ten Over]

I CAN build purely from the schematic. I've only got about 35 years of experience as an electronic technician, and I've worked on every kind of equipment you can imagine. Audio, video, radio, avionics, medical, test and measurement, pretty much every category there is.

But in this case I want to rebuild the amp to its stock configuration. And as it turns out, there is more than one revision of the Bassman 135 and as luck would have it, apparently all documentation and photos I've got for it are for a different version than mine.

It doesn't help that the work that was already done to it is also not for its stock configuration. My friend clearly had something different in mind, but I've found no documentation on what he was planning. I'm almost going to have to strip it back to a bare chassis to revert it back to the stock circuit anyway.

I noticed quickly that this amp doesn't have a choke. I'm contemplating adding one. And if I decide to go with a conventional output transformer rather than the stock ultralinear transformer, as luck would have it I do have a good spare Bassman 100 OT.

I bought a Bassman 135 when they first came out for the express purpose of cascading the channels and playing it at full blast. I didn't like it.

That early 135 had a Bassman 100 board in it with unused eyelets over at the PT end where the diodes and choke used to connect. I saw later 135's with the unused eyelets deleted, but the circuit seemed to be identical in both versions, so I'm wondering what different version you have.

You don't need to replace the OT just because it has UL taps. It will work fine as a conventional output transformer with the UL taps taped-off.

[Stevem]

Unless you where going to use this amp for bass playing and your where to be using it cranked up enough to need all of it’s available RMS power, then I would not bother with stuffing a Choke onto / onto the circuit.

If you go to the Fender amp field guide site and look up a blackface Bassman you will find the schematic and a chassis layout offered.

A lot of the way that layout was done in those amps can be directly applied to your getting that amp back to very close to stock.

The main sonic up grade one can make to any amp is to make the grid runs as short as possible and placing the plate decoupling caps as close to the tubes that there
feeding

Unless your starting from scratch this does not make for a clean looking build, but it sure helps with unwanted circuit interaction!

[pdf64]

Note that power amps and their power supplies are designed as a system (hopefully at least), rather than on a mix and match basis.
The 135W has a higher HT, presumably to get a higher anode efficiency, than the previous versions.
To avoid anode over dissipation, the OT impedance is higher (about 10% as I recall), and the secondary has separate taps and a switching jack arrangement to accommodate likely load options / avoid too low a reflected impedance to the primary and the consequential potential for anode over dissipation.
The use of OT tapped primary for the g2s was probably to keep g2 dissipation reasonable, taps are at about 12% rather than typical UL values.
It may be worth bearing the above in mind if considering a different OT or output device configuration.

[Matthews Guitars]

Yeah, I'll probably just try to rebuild it to stock condition, and when it's working right, sell it and let somebody else do what they want with it.

I've got a Fender 400PS to occupy my time when I'm not busy working on my '63 Tremolux, '67 Vibrolux, and '65 Super Reverb, all of which are other project amps I'm trying to bring back to life.

[Stevem]

When you say that you have a 400PS to occupy your time, do you in regards to repairing it or playing thru it?

I have brought 2 of them back to life over the years and even thought they weigh more then a SVT, at least the amp is all on one chassis and you go not have to make jumper cable as with the SVT to get the two halves powered up on the work bench.

The SVT is a real great sounding Bass amp, the 400PS is like a huge wattage Twin reverb that needs 3 cabinets that can handle 135 watts each.

Oh, did I forget the road crew that’s needed to move either of these amps to a gig, lol!

[Matthews Guitars]

I'm bringing the 400PS back to life. It had already been rebuilt by a friend of mine but he didn't complete the job and he's dead now so I don't expect him to finish it.

It's only got a little bit of work left to do to complete it. Reinstall the reverb transformer that went missing, troubleshoot a volume issue, and then it should be ready. A couple hours of bench time should do it. As of now it functions as an amplifier so all the heavy work is in the past.

I took a few minutes to put a new output transformer into the Vibrolux to replace the bad one, and wow, did that make this amp scream! I can't believe how much overdrive it has!

[Ten Over]

Yeah, I'll probably just try to rebuild it to stock condition, and when it's working right, sell it and let somebody else do what they want with it.

In that case, this might help.

Fender Bassman 135 Layout.png

[Matthews Guitars]

Thank you! That will certainly help!

[Ten Over]

New, improved layout. Added color and made a couple of corrections.

Fender Bassman 135 Layout.png