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Old 22nd November 2010, 01:30 AM   #1
johnmik is offline johnmik  United States
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Default MPA 3250 Amp

Hi Peeps:
I have a Signature MPA 3250 Monster AMP ( 3 channel ) I'm curious to know if anyone knows of a source for a "Service Manual" not the owners manual, I have that . I have an issue with it kicking out when it's cold and suspect the relays or the overpwr trip circuit. It kicks out even when not playing with zero volts in even.
Anyway I'd be happy just to get a schematic.
I contacted Monster and they refered me to a repair center down South. I live in CT. and the AMP weighs in at 92 lbs. Yeah I'm going to ship it to them and back... Thanks for reading.

John Mik
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Old 7th December 2010, 09:38 PM   #2
johnmik is offline johnmik  United States
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Default No documentation ??? WHAT!!!!!!!!

I just got in contact with the "Authorized Monster Amp" repair people and I talked with the one tech that works on these. There is no service manual or schematic available for the MPA2250-MPA3250 great!
He only would point out that noise is generated within and that's what kicks these AMPs out. OK???

Then he said he would have to kill me if he told me ... NOT really.

I'm having a problem with the AMP kicking out when it's cold, no input or whatever input. But it works fine when it gets warmer. Oh well out comes the scope and in we go....

If someone could shed some lite on this PM me please.

Thanks peeps.

John Mik
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Old 19th July 2011, 10:34 PM   #3
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I see lots of these with the same problem. Have to turn on several times, or won't turn on. Maybe a current-inrush limiter, or soft-start circuit? Protection system? Maybe self-latching relay? Maybe the main rail filter caps are about gone and it sucks too much current at start-up?

Anyway, if you find out...please let me know! Cascode VAS, ballanced/symmetric, FET outputs, almost sounds like a Nelson Pss design but it's really dedigned by Richard Marsh. Good quality caps etc. Look at this: Marsh Sound Design ~ Experience the Sound with Marsh Sound Design Products !!!
and notice on the main page of the Marsh Sound Design website, what amp is he using in his personal system?
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Old 21st July 2011, 08:14 AM   #4
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uh, I think it's a 2250 in the pic. And they run hot, but I doubt they're biased as high as a Pass would be. Still... When they were discontinued they were discounted from $2999 list to $700 clearance new. So used they're the same as a 2250, with an extra channer for free, and anywhere from $450 to $1700. I got mine with a turn-on problem for $205 on eBay.
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Old 28th July 2011, 11:16 PM   #5
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Found the problem with my 2350. But it's not techincally really a "turn-on' problem. Nothing on my front panel works, but the amp still works without a front panel even plugged in. Displays are all '7' and buttons don't work.

Turns out that the 3 heavy toroidial transformers are eaach mounted with a bolt thu the middle. The bolt is a bit long. In transport, if it's shipped sitting o its face, the weight of the transformers causes the bolts to scratch thru the traces of the display board. Might be repairable, assuming it was powered down when the damage occured (which is likely). Yep, damage at 3 places, each lines up with a x-former mounting bolt...
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Old 29th July 2011, 06:29 AM   #6
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I repaired all the cut traces, and one solder spot, but the display and buttons still don't work. Could be blown components on the display board, or could even be the controller board. Not even the power swtich works,
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Old 20th October 2011, 07:30 PM   #7
johnmik is offline johnmik  United States
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Default MPA3250

Well to just follow up on this problem. Got a schematic and I scoped out the unit I have and the protectection stuff is quiet. So I started moving stuff around one day and hooked up my Kenwood KT-8300 FM tuner directly to the amp from the variable outputs. Turned amp on and still kicked out some. Turn tuner on and problem is gone with an input. Tuner first amp on 2nd no problem. hmmmm...
So took a wire and grounded the 3250 chassis to my Kenwood KA-9100 chassis which I use as a preamp and run all sorts of stuff into the inputs. Everything works now. Seems that this puppy (at least the one I have is sensitive to gnd noise or whatever) needs more gnd connect than just the shield of the cables. Plus running old vintage stuff with no third wire gnd and new stuff with it, seems to cause problems (sometimes).
So now from a cold start all is well in stereo land for now. Until my next configuration change.
Man this stuff is fun.

Later
John
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Old 14th November 2014, 11:57 PM   #8
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Quote:
Originally Posted by johnmik View Post
Well to just follow up on this problem. Got a schematic...
Later
John
You got a schematic?? Please please share!!
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