I just bought this rare Stage Lead. There's is very little information about it. I read that it is a simple version of the Beta Lead. Is there somebody who knows anything about this amp?
There's VERY LITTLE available on the non-standard Sunn SS amps, I talked to Fender's dudette in charge of the brand in the late 90s who had worked at the company from the 70s to the early 2000s (when I lost track of her) trying to get a schematic on a Solos II.
Be aware there are very few techs who touch these SS amps, and cost of repair will almost certainly exceed value if it's something more than jack/pot/basic 'failure through use.'
Saw a bunch of that model in Chicago in the old days but it was a bottom-end backline item at grungy clubs etc and nobody cared. They do survive the apocalypse though, but won't be particularly loud by today's SS amp standards in the same package a lot of the time.
One thing I do recall from the Solos II I first got that carried over to any of that era's stuff: some models and variants will require you if effects loop is present to jumper the in/out to get any sound. The second one didn't care, so it could have been a jack issue but it was one of the first things I was told to try when #1 died.
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My pedalboard costs approximately 191 Metal Zones.