Franken-Champ

[mattm]

Hey guys,

The other day I got an amp from a buddy. Fender Vibro Champ that looks to be from 1968. A bit closer inspection shows that this thing has been heavily modified and I'm really curious as to how or why.

Backstory (ignore if you want): A friend died suddenly last year and his family gave all of his music gear to another friend. They were going to donate it but he happened to show up at the apartment before the Salvation Army did and the brother of our friend who passed let him grab what he wanted before the rest got donated (the entire apartment was being donated, he was a hoarder). Anyway, no one knows where/how/why he got any of the stuff, if he did anything to it or what he did, etc. All a mystery, he was a bit of a loner. He was also part of building the internet back in the 90's, bell labs type stuff and very versed in electronics and sound and being paid to research it. Not sure if he did the mods or not but I could see him hacking the amp at some point.

Ok, the amp. First I noticed it's missing the aluminum edge stuff and has a bunch of screws in the front. Turns out someone took out the old 8" speaker and installed a 10", 8ohm one. I guess the trim didn't fit. They also front mounted it which makes sense since there's no way it would fit rear mounted unless the baffle was quite a bit thinner. Since it was modded I decided to open up the amp and sure enough it's heavily modded.

Looks like a new transformer was added to it, or a second one. It's a fender from 1968 (original black one is 1967, not sure of brand). The original black one was removed and turned 90 degrees, the chassis cut to accommodate. This was done so that a bunch more stuff could be added to it including some giant capacitors (I think that's what they are, lol, have to admit my knowledge is very basic here). Looking at the circuit without even comparing it to the original it's easy to see that there are new modifications like some new resistors that have the dent in the middle vs the straight sided cylinders that are original.

The chassis is also damaged, dented in, which I'll fix since it's messing up a knob turn and also might be causing metal contact that shouldn't (or I'll get whoever fixes the amp, if I get it looked at, to do it since I don't want to kill myself, lol).

Anyway, it'd be really cool to shed some light on this thing (and also know if I should tube it up and turn it on, lol, don't want to do any damage).

Google drive with full size versions a bunch of images (zoom way in): https://drive.google.com/open?id=1B6...KZ4cT7T3NMIF_W

I was going to link a schematic but there seem to be different ones in google and I have no idea how to identify what would be an original vs mod vs someone drew one up, etc.

Fender Vibro Champ AA764, pretty sure it's 1968 because of the vertical lines that were abandoned after '68 but there could have been some face plates left over in '69 that got used so it could be a '69.

Picture of an original vibro champ (from web, not mine)


Back when I got it. Two 6L6 tubes, no 12ax7's. One 6l6 in the power, people are doing it. A 6l6 instead of a 5y3? Also notice the extra transformer on the right? Has Fender stamped into the metal but I don't see it on original vibro champs


What's left of the original paper inside


The small transformer in the middle (I think it's a transformer??)


Original black one that's in images of vibro champs online


The one that looks to be extra and has Fender stamped into it


The original transformer, chassis cuts can be seen and it's been turned.

[mattm]

Here are some pictures of the circuit:

The rest are pictures of the circuit. Loads of extra in there...

[eschertron]

That's some crazy work in there! You really aught to chart it all out before putting the circuit back to stock.

edit: and welcome to the place

[Justin Thomas]

Without a schematic it's hard to say, but my beat guess is someone added a 6L6 & made it a push-pull amp, hence the addition of the larger output tranny on the right. I see the power tranny is replaced as well.The small one is likely the original miniscule OT. 2x12AX7 & 2x6L6 is all tgatsneeded for a standard Fender "Normal" channel.

I personally would get a schematic drawn up before tubing it & firing it up, although as hacked as it's been you probably won't hurt any value if you do... I personally would rather have a Vibro-Champ though.

Justin

[mattm]

Thanks guys. I think this is beyond going back. The chassis has been drilled and cut, for one thing.

Along those lines: Technically there should be two jacks on the bottom of the amp, one for the speaker and one for the vibrato pedal. Someone removed them and drilled two holes in the back of the amp (one of them through the words "Vibrato Pedal" and the other to it's right) and put them in there. The transformer on the right is attached to the left of the two jacks and it's attached to the right hand one. I'm guessing that speaker in left and the right was added for an external cab.

Could that be the reason for the mod? Add an external cab, more power? It was my buddy's and he passed so I'm wondering did he do it? Why modify a vibro in this way vs a regular amp and keep the vibro? Also, given the vertical lines of the faceplate, it's a rare amp so why mod it at all?

The black transformer. Looking at it closer I don't think it's the original, it's too big (looking at pictures there is supposed to be a black on there but not that big, there's no way that one would fit in the original hole).

[Justin Thomas]

Why mod this amp? Because a design with 2x6L6 will put out at least 4x as much power as a measly little old Vibro-Champ at 6W. Randall Smith of Messa-Boogers started out making 50 & 100W monsters out of 15W Princetons...

I still say draw out a schenatic of it as is & put it here so it can be scrutinized for sound & reliable design. Look at any Normal channel on a blackface or silverface Fender, and I'll bet you have something similar. But that takes both 12AX7s to do.

Justin

[Justin Thomas]

Adding extra speakers does not add power. Adding two much larger transformers and an extra power tube does. I have to ask, are you up to the task of working on this yourself? And are you aware of the potential danger & safety concerns working on this yourself? What's your experience level with high voltage, tube circuits? What tools do you have? Destroying an amp, serious bodily injury, or death to amp &/or self, although possible, well, we really don't want them to be an option...

Justin

[Leo_Gnardo]

It was my buddy's and he passed so I'm wondering did he do it? Why modify a vibro in this way vs a regular amp and keep the vibro? Also, given the vertical lines of the faceplate, it's a rare amp so why mod it at all?

There was a time, believe it or not, when Champs didn't get much respect. And they sold for small money well into the 80's. I bought two working Vibrochamps then, mid 60's blackies, for $60 each. Broken ones could be had for $20.

Looks like your friend went full "Boogie" on his. Crikeys, he wedged in some BIG transformers! Given the cheap price, the fact that back then they were common as crap, nobody much wanted 'em, they were prime for drilling up. One of mine served as my workbench test amp with a minor mod, a switch near the input that selected normal, bright, mellow. When the Champ craze took over, I removed that one from bench service worried it might get smacked with a tool or splashed with paint or blood. A customer gave me $600 for it and that paid the rent for a month. The other one, I confess I boogied it up but no huge transformers. Just put in a Deluxe OT, pair of 6V6, solid state power supply, cascaded preamp stages for rippin' gain, and wedged in a 10" Peavey Jaguar speaker. 19 watts at clip. It was a little box of dynamite, and served as the rock star's dressing room warmup amp for many tours. Finally another customer bought that one for $800. What happened after that, is between him and his neighbors.

Since then I don't drill up blackies anymore. Well not much anyway... And in recent times I'll spare the silvers if they haven't already been boogered up. What mods I do are "stealth" that is hardly noticeable to the eye, and easily reversed should the owner decide to go back to stock, sometimes in an effort to pry more loot out of the buyer's pocket. It's happened a couple times.

[mattm]

Yeah that's what I was thinking, when it was done it was when they were just cheap amps. The only thing that makes this one special is that it's one of the first of the silverface models.

As for working on it? I definitely won't. I'd kill myself and burn the house down at the same time. I think I'm going to get someone to make it work as is. I have a feeling my buddy did it and it'd be neat to have his mod around. Sentimental value vs vintage amp value.

I put some tubes in it and turned it on. It turns on, the tubes light up but there's no sound at all. No smoke either, though, so that's good I hope. That's as far as I'll go with it. I was more curious as to how it was modded and why it would have been done. As in, as is, what is the current design intended to be/do? Why modify it so much? There must have been a purpose...

And yeah, adding speakers doesn't add power. I meant would the reason for the mod be to add more power to the amp so that it could power an external cab, more sound from an amp someone had lying around? Or would this mod have some tonal reason?

[mattm]

Just noticed the 4x more power comment. Maybe I will try to draw it out myself. It's been a long time since I switched from electrical engineering to programming but hey, I just hit my 40's, why not? As long as I'm not the one playing with power, lol.

One thing I keep thinking: Would someone buy it like this? Outside of a blind buy it's very obvious that it's been modified so you'd have to be really dumb to be ripped off in that regard and my buddy was definitely not dumb. That leads me to wonder: Did he do it?

On the chance that he did and since it's so hacked anyway, I think it would be fun to get it working as is. Even just pretend he did it. A little piece of himself that will last forever type deal... Worth way more than any monetary value.

[Leo_Gnardo]

And yeah, adding speakers doesn't add power. I meant would the reason for the mod be to add more power to the amp so that it could power an external cab, more sound from an amp someone had lying around? Or would this mod have some tonal reason?

No "extra power" from ext speakers, BUT different speakers, and cabs, do sound different. Run that amp through a closed back 4x12 for instance, it would probably blow your socks off. Even an unmodified Champ sounds way more awesome through most any kind of external speaker that's bigger than a tissue box. For the nonbelievers who visit here, I'll plug a Champ or any other tiny amp into my Ampeg V4 4x12 loaded with Altec 417's and they become believers real fast. Even in spite of the impedance mismatch .

Should you decide to sell, don't neglect our own "Flea Market," costs nothing to advertise & maybe some MEFster might like to take on the project. Or pry those big transformers out to use on something more appropriate. With all the photos & explanation you gave here, it would save having to do it all over on Reverb, ebay or craigslist. And if you decide to tackle it yourself, you could not possibly be among better company to give hints & help right here.

[shortcircuit]

All this modification yet no grounded plug ??

[Justin Thomas]

I will still bet that your buddy was trying to turn it into a 2x6L6 Fender "Normal" channel bare-bones amp. That would be somewhere between 35-50W depending on what actual transformers & power supply was put in. So yeah, way better than a 6W Champ. As for any vintage value, toast likely unless you part it out. Have a schematic drawn out & get it going - you'll have a firebreather for sure.

Justin

[Chuck H]

I have to question the viability of 6l6 tubes (particularly of dissimilar make?) in such a small cabinet. The sheer wattage two such tubes can make would beat the innards to smithereens Perhaps if the voltages and OT primary impedance are suitable a pair of 6v6's might be better??? Just thinking out loud. But it's pretty clear that someone that knew what they were doing did this work. For that reason I would fix the amp up as it is and see how it rolls. Who knows? Maybe this was an early Randall effort!?!

As to any damage to a vintage collectible, I wouldn't sweat it. Not for an SF VC. That is, it's not a '59 Les Paul. More like a '78 "The Paul" No offence intended. Still a cool, vintage model. Just extremely oversold and outshined by other stuff. I've (heavily) modded SF VC's myself without a second thought. The likelihood that they will ever become coveted classics in the high dollar category is about the same as the Ford Pinto or Chevy Nova making the same leap. JMHO

[mattm]

"All this modification yet no grounded plug ??"

I thought about that as well when I was trying to figure out when the modification happened. Maybe it indicates that the modification was done before ground plugs on amps. Looking at the extra parts in there it's hard to believe if he had those lying around and used silicone or whatever to hold the big caps, surely he'd have had a ground plug lying around as well...

One thing is for sure: This is a lot of fun and thanks guys for helping me with the little mystery. I can't wait to hear the thing. I'm tempted to just take it in but another part of me wants to try to draw the schematic myself. It's not a complicated circuit on a printed board, it's just wires. Follow them and the direction, connect the lines to the part numbers except on a computer...

Anyone know any decent free schematic programs for windows?