I have a Carver M-400 power amplifier that has died. When you plug it in, you can see a sizable spark at the base of one of the large capacitors behind the power transformer. The amp then pops (if you have a speaker connected) and causes the LEDs on the front of the amp to flicker and jump to all various levels.
I cannot see any components that are destroyed (IE - bulging cap etc), but I have not tried replacing the cap that sparks (because I'm not sure if that's the issue or a symptom).
I bought the amp for under $50 some years ago and have an estimate of a significant amount more to have it fixed, so I'd rather try myself.
Sizable sparks at a cap~ base?? That sounds like there may be a dead short somewhere and/or catastrophic failure of the caps~ (not always visible on the components, use a multimeter to check the terminals if they are shorted.) If there is noting else that has failed in the amplifier other than the power supply* (*if applicable), it is repairable. Otherwise good luck finding the other fault(s)*.
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I have a Carver amp which developed a "hum" also. As a troubleshooting step only (long term this is NOT a solution) you can use a ground plug adapter that removes the ground lug from the unit. This is an adapter that has THREE (Line, Neutral, Ground) female sockets for the amp to be plugged into, and TWO male plugs to go into a wall socket. If the buzz goes away, you've got a leaky capacitor in the Power Supply section of the amp. It will take some doing to actually fix the problem, but this will narrow down the cause.
If the hum disappears when you unplug the input audio cables, you need to use BALANCED lines to the amp. Read up on balanced lines and XLR connectors and TRS connectors. Find the subjects of those on google.
Carver designs in general are not easy to repair. I would recommend that you send this unit into a Carver authorized service center. The likely problem is the output transistors, but the driver circuits and predrivers are not simple designs and if there is a problem there, it could effect the outputs. Tracing this will require equipment and schematics that I don't believe are available on the net.
You need an amplifier with at least 200 wpc to get the most out of your BOSE. Look into getting a NAD, ADCOM or CARVER amplifier. I prefer CARVER myself. I am running a CARVER M-500T(251 wpc) on my 901's and they sound incredible.
I can think of no reason any amp pushing 120 watts would not work with 901-VI's. They're very efficent and will probably play louder and cleaner than you would ever need. As I recall, my old series IV's have no maximum amplifier rating specified, but I did blow up a bridged Carver M-400 Cube (pushing 400 watts to one speaker with a DVD-Audio of Yes - Fragile cranked dangerously high) with them. I'm convinced my speakers are indestructible in any home application.
Keep in mind that whatever you decide to use as your control/amplifier section, a pair of 901's need a dedicated stereo amplifier. I suspect you're thinking surround sound so a receiver with separable preamp/amp channels, due to the Activbe EQ, would be needed and as far as I know they don't exist. A separate stereo amp for the 901's was my solution. I run a Carver AV-406 (5-channel amp) for my 901's in Front, 2 Subwoofers and the Rear Surround channel, with the Active EQ between the receiver and the 901's amp channels. My receiver controls everything and just drives the Center and Surrounds.
Modest amps would work but at very loud volumes may go into clipping, which is bad for any speaker. 120 clean watts is good. I'm using only 110W for mine.
A Carver M-200 is a fine, efficient amplifier that would have you cooking just fine (2x100W).
I found out through the Carver Audio forums that metal shavings inside the case are an issue with this unit. So I used an achohol based spray and cleaned the switchs and the circuit board, (there was a fair amount of shavings found). It has been running for 14 hours with no problems.