65 Fender Silver Blackface Dual BoogieMaster Reverb... Need a little Help!!

[OneTwo3]

So I have this.... uh, Fender amp that has a Boogie MKII (562003) OPT and a '65 Twin/Showman PT, with 4x5881 power tubes, 7 preamp tubes...
Reverb, Effects Loop, ( with relays?) 3 push/pull pots, Vibrato, Neg Feedback pot, Bias test points x2 with 2 Trimpots, Half power switch on the back, one input with a gain and master, and a second channel with a gain and another gain.... and a pot under the chassis that I can't figure out yet, might be for setting the center power tubes voltage? or maybe for the transformer or something underneath the chassis that seems to have a transistor or two mounted on the doghouse.

So I pick it up last Sunday for a song, with a bandmaster head cab sitting next to it I couldn't even turn it on, took a chance and brought it home.

It works.... to a point, but has a couple of problems that I could use some help with; the tone stack seems to work okay and other times it's wonky..
There is a blue wire coming from the bass pot ( push pull) that is coming from a cap/resistor and is just hanging loose, no idea where it should go..or if it is one of the reasons the bass pot doesn't do much.
There is another white wire coming from under the board thru a hole near the opto-bug that is -1 volts leading nowhere.
There is a cap on the back of the second pot that is not connected on one end, the other end is on the 1st tab, then the next tab has the lead from the treble pot.

It's kind of a nightmare for my skill level. Without a schematic, it's really tough tracing things because of all the extra wires and two extra circuit boards and all.
The input jack lead is to the 3rd preamp tube, pin 2.

The 2nd gain channel is very hot and tasty, as is the first when it's working well. The reverb and trem work. The plate voltage is 440V and the bias tested across the resistor is at only 16mv.

I twirled the pot under the chassis, next to the power tubes, and the voltage changes from 25 to 75 volts on the output terminal, but it's hard to tell why and where that is used...

What I'm hoping for is a little advice, encouragement and direction in what to do to get it up to it's full potential... maybe you recognize something that tells you what schematics were followed or something ridiculous like maybe YOU built it

I realize that I should pull all these pots on the front and clean the mounts for good ground, I think some may need replacement, but I also think it's got something going on with the wiring that isn't quite right- on the 1st channel, the volume can drop out if the tone pots are turned too far one way or the other, but not in the 2nd hotter channel. I sprayed them all today and it's not much of an improvement. It gets louder with the treble pot on 0, same with the bass pot. The 2nd channel never has a volume drop issue but no response to speak of from the tone pots.

I think this one has some real potential, but it might take me all winter long to rewire it from scratch or something.

I've got some pics and if nothing else you'll enjoy looking at this and telling me "good luck, buddy !"

[distorto]

Wow. My house caught on fire just looking at the pictures. I'd probably gut it, access the damage and rebuild to something that resembled a guitar amp using the transformers, sockets etc. (and build a jukebox, a pinball machine and a model train set with the left over parts) Wow. Welcome to the forum BTW.

[OneTwo3]

Thanks, for the welcome and the laughs
I hear the relays click on the small breadboard when I power it on.. I think maybe those are there to switch the effects loop on and off, or maybe reverb too, otherwise why would they be there?
There are 2 push pulls that don't seem to do anything, and with that blue wire loose it could be you pull the bass pot and switch something, or else it's a tone shaper... but the third gain knob wich works on ch2 doesn't switch anything noticeable either, tonewise or any other.
I just want the jukebox in the amp to work!
There is a lot of hum on ch2 with that 2nd gain knob turned up all the way... need to fix that.
It sounds Really good with a Greenback, like nothing I've heard before. Sort of Dumble type gain, smooth clean tone too, rounded and compressed slightly, and the neg feedback responds well.
It might even be Simul-Class potential, not sure yet but I see that some of the leads from the Boogie transformer are not in use and coiled up near the choke.
Maybe that pot near the power tubes change plate voltage on the center pair of tubes or something.
I have a lot of work to do, don't I?

[Enzo]

Oh, it looks like someone installed an extra heater transformer over inthe corner, either to power extra tubes or to make a low voltage supply for those relays yo mention. Probably the latter. That would be the thing on the cap vault lid. If I had to guess, the little square board with the pair of 10-turn trim pots is probably dual bias controls. See if there is something in the neighborhood of -50VDC on those trimmers.

But really, it would be a Herculean task to fathom what all has been done to this, so unless you can find who did it, you may never find out where some loose wire should go.

New PT and OT shouldn't matter much, they'd be wired the same. If that is the original eyelet board down under all the other spaghetti, then the amp could be restored to stock pretty easily.

I have no idea what they did, but all those shielded cables are carrying signal, I would bet, so perhaps there is some sort of channel switching added. Maybe the Normal channel, which no one uses was wired to be extra gain stages that can switch in and out of the reverb channel.

[Chuck H]

FWIW this looks like Torres boards, component brand choices and relay assy. Probably done by the owner with "kits" bought from the Mac printed catalog that Dan use to distribute. If Dan had done the mods there would be a "Torres" sticker inside the chassis.

What is your goal? do you want to keep the amp the way it is and make it work or do you want to return it to stock or do you want to change something about the way it is but not keep it stock???

[OneTwo3]

Well that helps a lot, thanks for taking a look-

I checked the Torres pages and found a link to the older mods, here:
Older Torres Kits - the basis of it all!

This amp has a master with 4 wires on it, might be something like this, it does tie into the PI section:

"Provides superior tone at high and low volumes. Can be a new installation or replace an existing master volume. One of the most amazing kits you can install on any amp, even if it already has a master volume.

For Fender amps made before 1986 (Two or four power tubes) and the Marshall JCM 800, JMP, Super Lead, Super Bass Original Plexi, Reissue Plexi, JTM45

The dual stage master is installed in the Phase Inverter section of the amp. Here the signal has been split into in phase and out of phase signals to drive the power tubes in push pull.

Since it is now controlling two signals the tone is much fuller and not thin at all. It also allows you to overdrive the Phase inverter tube - which other masters do not. Quite a bit more overdrive available"

No Torres schematic found yet, might help.

I think the extra pot near the power tubes may be for the parrallel loop level, have to check that out.

My goal? Make it work so I can use it or sell it! Reverting back to stock is not going to be a big help in selling with all the extra holes in the chassis, and the one extra hole in the "Dual Showman" silver faceplate...

I originally thought some builder may have done this who stamps their own serial number on it, if you look at the back there is a riveted serial number plate with "123854" on it, no letters, and behind that there is 3 holes drilled, maybe thru the original serial stamped in the chassis?

Now I realize it's just a hack butcher job that has good ideas poorly executed.

The little transformer on the doghouse buzzes, maybe that's where the hum comes from.

I feel better about my cluelessness hearing Enzo chime in that's it's a Herculean task.

[distorto]

"My goal? Make it work so I can use it or sell it! Reverting back to stock is not going to be a big help in selling with all the extra holes in the chassis, and the one extra hole in the "Dual Showman" silver faceplate..."

If you did decide to revert it, a new faceplate available from Mojo Musical Supply or some other repro. amp parts supplier could cover the extra holes and make make it more attractive to potential buyers. I could be wrong but I sorta feel that unless you resell it for a song it's not going to garner much $$$ as a mystery science project. Just something to consider while you gather your options. I for one would love to restore something like that but that's just me and I tend to dig restoring stuff in general. Good luck with whatever route take and keep us posted.

[OneTwo3]

Yeah, maybe a blackface faceplate to match the long tail Fender emblem.
I really dig the extra gain stages but there could be one less knob
I think that maybe the transistors on the doghouse are another gain stage, the buzzy one getting noise from the failing transformer.
I just plugged a cord in the loop, and the amp is louder that way, but the knob underneath by the power tubes has no effect there either.
It's also a short head with no room for the reverb tank, so it's really in need of a combo cab or tall head.

Does anyone have an idea where the Torres pull bass boost lead is supposed to connect?
If I get the tone stack working right and loose wires in place I'll leave it alone while I figure out what to do with it in the long run.
It sounds seriously good, never heard a Twin with this much gain!

[OneTwo3]

I figured out that the extra pot on the bottom near the power tubes varies the heater voltage!
I get 4+ volts on the power tube heaters and 10 volts on the pre's, if I increase the pot to 6.3 on the PT's I go from 10+ volts at the pre's... to 12+ volts- whacked!
And the bias trimpots don't do a thing, must be wired wrong... there are 2 220K resistors on that little board, and two 4K ohm resistors? I would have expected two 1 Ohm resistors there.
The extra white wire is for the tremelo on off footswitch that's missing it's jack.
The blue wire from the bass pot could be used to turn the loop on and off I hope, it jumps from .1 volts to 3.8 volts if I pull it...
Biggest problem it has is the tone stack has crappy pots and sketchy wiring.
It's a damn shame they drilled a hole in the faceplate just for a negative fedback knob when it's not all that useful and could have been switched by the ground switch or a pot on the unused trem jack hole would have been much better.

[OneTwo3]

Also like Enzo suggested maybe one of the transformers added underneath were for extra heaters for the extra preamp tube...well it is a 6.3 volt transformer.
However the Twin reverb PT should have been enough for 6 preamp tubes, what about adding a 7th pre without an additional transformer?
Shouldn't that be do-able?
If they were trying to heat one tube with an extra transformer, they really goofed that up.

[Enzo]

Don't overlook I also suggest it could be to make a small supply for the relays.

[OneTwo3]

Pins 4&5 are not connected on the preamp tubes.
I better strip this down and start over.

[Bruce / Mission Amps]

Pins 4&5 are not connected on the preamp tubes.
I better strip this down and start over.

As dear old dad used to say... looks like a bucket a smashed assholes.
Gut it and build a good amp out of it. There are lots of real Fender mods out there that will make you very happy.

[Prairie Dawg]

@Bruce you left out the second part of the statement: "-with all the pretty ones picked out."