Saturday, January 10, 2015

Repurposing an Ampeg SJ12T combo Part 1

A while ago I acquired an Ampeg (SLM) SJ12T combo because it sounded interesting. In a word, it turned out to be a complete dud. The reverb and vibrato went out to lunch and they haven't been seen since then, and no amount of endearment could get them to come back and behave.

I mean, the idea sounded good-an all American made tube amp, 50w, single Eminence speaker, reverb and vibrato. Who wouldn't have loved it? Of course, as I mentioned the reverb and vibrato were dodgy, they went out for lunch and never came back despite all my efforts, not to mention intermittent crackling and pops, and there was absolutely no way this amp could deliver 50w-not now, not ever.

So back in behind the water softener it went, to do its term of incarceration for felonious misconduct while I figured out what on earth I was going to do with the thing.

I pretty soon came up with the idea of repurposing it, and it's turned out into an all out project, which means that this is going to be in several installments. There are a number of reworks that are needed so I've had to figure these out as I went along.

After a lot of study I decided to ditch the cheesy reverb and build something close to a 6G3 Deluxe with octal preamp tubes and vibrato. There was room to broach another socket hole so in it went.

Next, I had to figure out how to get dual volume and tone controls. That was easier than I thought as I had two stacked dual 1 meg audio taper pots. Between that and a couple of switches I could have normal and bright channels and bridge them as well with the existing holes, opened up a little.

Considering that the output transformer seemed stingy on the iron for anything close to 50w, I decided a ClassicTone Bassman output transformer I had was just the thing, and it could be located more or less in the same neighborhood as the old one which can find a home in some other project.

No comments:

Post a Comment