
What we have... (well, we... I) are two Fender Vibrosonic Reverbs from the mid-70s. 100 W master volume model. One I've owned since 1989/1990 or so, the other since last year. The one I've had for aeons was modded before I got it; it has no reverb but instead it has an extra gain stage. The other is more or less stock, save a horrid carpet upholstery job which will be tackled at some later date.
All 100W Fender guitar amps from this period are the same except for the face plate; the difference lies in the speaker combos. All but this one, I should add... the Vibrosonic has a different output transformer. But that should be the only difference. Anyway, this pictorial should be of equal use for a Twin, a Quad reverb, a super 6, etc.
Both my amps still have the original Mallory caps, and since they've been playing up over the past year, some servicing is in order, if not long overdue. Unfortunately, I've always been scared shitless of big tube amps due to horror stories about stored voltages. Brad was very effective in replacing my fear by some knowledge, to the extent I now know how to safely discharge these amps. I actually did that months ago already, so no pics of that. I'm the type of person to check whether I've left the oven on three times before I go out (and at least one time as soon as I'm out the door), so I checked the voltages on the caps anyway. They're empty

MIke (OffYourFace) was so kind to point me towards an eBay seller with great prices on sets of caps for this model. His shipping was insane though, so instead I paid Mike to buy me two sets and ship them to me. Yay for the Indo brotherhood

OK, first the carpet amp.
Can removed, and here are the filter caps:

Getting them out was quite easy. Just heat up the connections, and they fall out. The only tricky thing is not melting the mantle of the wires around them, but with some careful bending out of the way, that's not really hard. ONly the middle one is a bit tricky, since five different things connect to one of its eyelets.
OK, all out, first one in. Not very educational, is it?

Brief intermezzo. I'm old-fashioned, so I like to put tin on everything before I put it in a circuit. Nothing as annoying as having to work with blobs of solder when you're fucking about in a circuit. So, I cut the legs to the appropriate size, and then put tin on them, over quite some length, in case I need to trim them further (don't want to cut off the tinned bit). This probably isn't necessary, it just makes it a tad easier.

Solder one side, bend, and trim to put the other side in place. Of course, observe the correct polarity of these things, you don't want to put them in the wrong way.

Since the 20 uF Sprague caps are a bit smaller than the Mallorys, I thought it smart to bend them in place in order to trim them to the correct length. The big 100 uF caps are roughly the same size as the Mallorys, so those I just trimmed them while holding the old Mallory cap next to it.

All in place. A few good yanks on all the wires just to make sure everything is connected tightly. Final polarity check. Everything is as it should be. The can can go back on, but in general I find it smart to wait until more knowledgeable people have checked out what I did. You don't want to re-assemble your amp just so you can dismantle it again after someone points out something fatal while looking at your pics


Of course, next step is the remaining electrolytic caps on the main circuit board. Dinner first.
And oh yeah, a local tech asked € 300 to do this. I just saved about € 250.
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And on we go to the main circuit board. There are a number of electrolytic caps there. They all look fine, and one has been replaced already, but hey. The kit was a complete set, so I might as well change them out all at once.
Most of them look like the silver one in the top of the image, the black one next to it is one I already installed before taking the pic. There's also one that looks milky white on the main board.

Replaced:

Then there's the big ones. The silver one is a replacement already, and it's been glued to the board. I'm sure that's very functional, but also quite annoying, as I had to cut it off with a scalpel.

Easily replaced:

Pardon my French, but doing this really is a piece of piss as soon as you're sure the amp has been discharged. If you can follow simple instructions and now how to handle a soldering iron, you can't really go wrong (unless you have dyslexia so severe that you cannot tell a + from a - reliably)..
OK, next step is turning the balance pot into a bias pot, as per Al's instructions.