Anybody have a schematic for a Mini Brute I

[G._Hoffman]

Yes, I said I, as in 1, or one, if you prefer.  Its the one with one volume control, a treble/bass tone stack, and a bright/normal/dark switch.  Everything I've found on-line so far is for a Mini-Brute II or latter.  Not what I'm after!  The one place I've found it is charging $20, but since I'm told that Polytone usually sends them out for free - though apparently, for some reason, not to me - I don't really like that much. 

We've got two of them in the shop that we use for testing guitars (perfect amp for it - its dead clean, so any fret buzz or such shows up instantly, and balancing pickups is quick and easy).  But one of them is on the fritz - its fine when you use it with a lower output pickup, such as a strat or tele, but if you plug in anything with a humbucker it gets a REALLY nasty distortion.  It almost sounds like cross over distortion to me.  If I had to guess, I would assume that the bias is off on something somewhere, but I don't know where.  We've had this amp for close to 40 years, and it only started doing this about 5-6 years ago (I've been very slow to get around to fixing it, since it works fine on many guitars).  Also, our other - identical - amp doesn't do it.

So I need a schematic, and I've been told that Polytone is happy to send out schematics, so I called them up.  Stone wall, for some reason.  I think he was a little offended that we weren't gigging with these things, but he wouldn't send one to me.  I've taken it to one of the local repair guys, and he couldn't find anything wrong, but his only guitar is a POS thing with low output pickups.  And none of the other guys in town have any kind of reputation for solid state work.  They all know tubes, but transistors apparently don't appeal to them.  (I get that - really I do - but it isn't helping me at the moment!)

So, if you have any suggestions for a link to the schematic, or if you have one you could send me, PLEASE let me know.  We really need this amp to work right, and right now it doesn't!


Gabriel

[PRR]

> I need a schematic

Why? You got one sick, one happy. Open both up. Compare: what's different?

Since it is related to pickup level NOT output level, I'd be looking at the first stage. Find the input jack. Where does it go? What are the voltages in that area, one amp to the other?

I don't even have a clue if this Brute is tubes or chips. But if you find a big cap (probably power bypass) with 15V in happy-amp, 2V in sick-amp, you are very close to the trouble.

[G._Hoffman]

> I need a schematic

Why? You got one sick, one happy. Open both up. Compare: what's different?

Since it is related to pickup level NOT output level, I'd be looking at the first stage. Find the input jack. Where does it go? What are the voltages in that area, one amp to the other?

I don't even have a clue if this Brute is tubes or chips. But if you find a big cap (probably power bypass) with 15V in happy-amp, 2V in sick-amp, you are very close to the trouble.

It's chips. 

The only problem with that suggestion is it means taking the good one out of service in a very busy shop.  They probably see 4-5 hours of playing time every day, spread through out the day.  It would be a BIG problem to have them both out of commission.

But I went ahead and paid the $20 for the schematic.  Now I just need to make the time to figure it all out.


Gabriel