Reference Post - Cooper "Vibrochamp" fix-up

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In this thread, I'll post the details of the repairs that this amp will require. Having some time available last night, I went over it a bit and took some pictures. The seller on ebay purchased a number of amps from the Indigo Ranch recording studio and had them shipped to the east coast, by Allied Van Lines. The blue labels are Allied inventory tags.
First pic has my Rotovibe leaning against it for scale.

 

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Left and right views of the faceplate. The faceplate has been bent out resulting in a concave aspect. Whether this was to stop a rattle or a result of pulling the chassis out for service, I can't say. One thing to keep in mind, many times when an amp has a footswitch or extension speaker on the front, the chassis may just be a piece of folded metal rather than a box, like Fender or Marshall. In this case, they folded the edge of a piece of aluminum to make the front. Interestingly, there are two #6 machine screws that pass through the side of the cabinet and through two tabs to hold the chassis down.

 

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Here's a couple shots of the back. Dues to the holiday weekend, I have to skip working on it. Dang visitors!

Here you can see the control pots.
Typical for an inexpensive amp, the volume control has a switch on the back to turn on the juice. there is also a switch on the vibrato control. On some Fender amps, the vibrato doesn't work unless a footswitch is plugged in.

 

[JerryR]

Jeesh - I'm so glad I only play acoustic - have enough trouble with the strings without all those wires n'things :shock:

 

[Guildmark]

Jeesh - I'm so glad I only play acoustic - have enough trouble with the strings without all those wires n'things :shock:

That was my mantra, too, Cryo-Jer. But here I am planning an amp re-build with my kids as our summer project. In fact, the one we bought on eBay just arrived yesterday. I'm afraid to even plug it in and see if it works, though, after Default and capnjuan's warnings!
I guess the real irony, however, is that your strings are wires, too!

 

[capnjuan]

I'm afraid to even plug it in and see if it works, though, after Default and capnjuan's warnings!

C'mon ... that's part of the fun! If nothing else, can plug it in and bump it on with a chopstick ... if nothing (bad) happens ... turn off ... plug in ... turn on! (sheesh ... sounds like something T. Leary would say ... :shock: ) CJ

 

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I was really hoping to get this one done in time for tomorrow. We have friends coming over and his son plays guitar. My oldest just started a little bit ago. I'll have the Dirt Road Special, the Maverick, the GA1 all set up in the living room.

Parents will be outside with some adult beverages. :wink:

 

[JerryR]

Jeesh - I'm so glad I only play acoustic - have enough trouble with the strings without all those wires n'things :shock:

That was my mantra, too, Cryo-Jer. But here I am planning an amp re-build with my kids as our summer project. In fact, the one we bought on eBay just arrived yesterday. I'm afraid to even plug it in and see if it works, though, after Default and capnjuan's warnings!
I guess the real irony, however, is that your strings are wires, too!

Hey, maybe that explains why I have so much trouble with them. Last night's practice was cut short when my G string snapped (no Grammy, not THAT one ) - thought elixers were supposed to last for ever, but didn't last any longer than my D'addarios :roll:

 

[Guildmark]

I'm afraid to even plug it in and see if it works, though, after Default and capnjuan's warnings!

C'mon ... that's part of the fun! If nothing else, can plug it in and bump it on with a chopstick ... if nothing (bad) happens ... turn off ... plug in ... turn on! (sheesh ... sounds like something T. Leary would say ... :shock: ) CJ

Well, I plugged it in. It worked surprisingly well. I plugged in my daughter's Squier Strat and it sounded okay! It's not loud, but it doesn't have a lot of heart, either. I actually had trouble getting it to distort, and winding down the Tone control just made it sound like someone sat down in front of it.
I showed my son the glowing heaters. "Cool!", he said. "Can I touch 'em?" I guess everyone has to once. After the ouch he asked, "Can I take it apart."
"Yeah. That's the idea," I told him. His eyes lit up brighter than the tubes!
We may start on the disassembly today. Will keep you posted.

 

[capnjuan]

Hi Mark; pics will help us cheerlead from the sidelines. Larger top-down views and others close enough up to read the colored coding bands on the resistors. And from this LTG thread Cleaner / lube for pots might want to get some of this CAIG stuff Can clean on/off switch, volume/tone controls, tube pins and sockets, and brush your teeth with it. Might straighten out the tone control nicely ... or not ... :wink:

 

[Guildmark]

Thanks, John! I'll be sure to use a tripod, too. Getting a good chronicle of this project is imperative for Huck's Creative Memories scrapbook.
I'm going to my local electronics store today, after stopping by to place a flag on my mom's grave. She was a veteran (AirForce - Korean Conflict) but the cemetery doesn't seem to know that. I will look for the cleaner while gathering some components, and I sure hope it's cheaper than Crest Whitening Strips!

 

[capnjuan]

... I will look for the cleaner while gathering some components, and I sure hope it's cheaper than Crest Whitening Strips!

... but keep in mind that Crest Strips won't clean your white wall tires!

 

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Haven't forgotten about this thread, but I have a metric crapload of stuff going on in the next couple of weeks. Benchtime should be available after the 22.

 

[capnjuan]

hmmm .... this may take a while ...

 

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I said metric not Imperial! :roll: :lol:

 

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Oh, HERE'S the thread I was looking for!

 

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After waaaaayyyyy too much time, I've got the tacochamp recapped, rewired and ready to go. Seeing as it's after 12, I don't think it would be wise to fire it up. :lol: I don't know whether to fire it up with the tubes that it came with, seeing as how they never took them out of the sockets when they shipped it. :evil: Still, I'm looking forward to some class A, Sylvania powered, tubey goodness sometime after 8am.

 

[BluesDan]

After waaaaayyyyy too much time, I've got the tacochamp recapped, rewired and ready to go. Seeing as it's after 12, I don't think it would be wise to fire it up. :lol: I don't know whether to fire it up with the tubes that it came with, seeing as how they never took them out of the sockets when they shipped it. :evil: Still, I'm looking forward to some class A, Sylvania powered, tubey goodness sometime after 8am.

It's now 10:30 AM......do you know where your tubey goodness is?? :wink:
Or did the fire dept. just leave?? :lol:

 

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Erk, I'm running it up on the variac now.

 

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It's up and.....

Tremelo is borked. If I have a tube plugged in the socket, I get no signal, just background hum. However there is fairly little of that. One of the tricks I've learned is to completely shield the chassis. Sometimes, the manufacturer cheaped out on the chassis and just uses a "tray" instead of a "box" for the chassis. This leaves the top, back and sides completely unshielded. The cure for that is metal repair tape, a thin metal foil with a very sticky adhesive on the back. You tape this over the cab and viola! instant shielding. It really made an audible difference. Replaced the woodscrews holding the handle on with a proper set of t-nuts.

Like I said, the tremelo is borked, but you don't need it. I have the old rectifier tube and a sovtek 12ax7 and 6v6 in the amp temporarily (yeah,yeah, I know, supposed to be the Sylvania :roll: :wink: ). I can see why No one wants to give up their Champ. Low volumes, very clean, pretty tone, get past 1 o'clock and it gets aggressive in a hurry. Dime it and it sustains for days.

This lil mammal comes with an 8" Jensen and the speaker overdrives fairly quickly. Speaking of overdrive...

My Starfire III pwnes this amp. The pickups just pummel the imputs. The Astrojet can put a pretty good hurting on it too. Haven't tried the Strat or my son's Tele on it yet. :wink: I didn't take any pictures, due to the high camera fatality rate around here. I'll take some when I fix the tremelo.
Got to get to the honeydew list....