Anyone know about the carver designed sunfire true subs?

[CJVx]

I had purchased one of these to use with my Magnepans. Bought it as a broken unit, hoping that the internet lure stating that these usually come back to life with capacitor replacement stood true. Anyway, it was a hummer, noisey and distorted sounding when I got it, replaced all of the electrolytics and the hum went away but there was crossover distortion and most of the negative sine wave was distorted and clipped as seen through my scope and generator through input through the usable range (20-100Hz)

There are two pots on the main amp board, one sort of helped with the crossover distortion and rounded the negative sine wave to an extent so I’m assuming that is the idle current, and the other pot “cleaned up” the sine wave a bit as in there was less fuzziness to it. But, when more power is pushed from this thing, it still is apparent my negative sine is clipping, and the whole signature gets nasty and fuzzy, so something is definitely wrong.

Does anyone have experience with these? Apparently any technical info is non-existent.

Thanks!

 

[blhagstrom]

No direct details.
Some gut feeling from experience with amps.
Clipped output signal always turned out to be a flacky transistor on the audio signal path.
Which one? Could be any. Output, driver, pre-driver, diff pair.

Tracing the signal path without a schematic sucks.

 

[Hobie1dog]

Lots of amplifier issues with these, it's what they are famous for.

 

[Ray Gianelli]

@CJVx , Does the sub look like this?


And does the waveform look like this?


If so, I had luck by cleaning all the pots and then hitting the solder joints on them.

Note that these subs were never designed to have a continuous sine wave run through them. I blew the fuse on this one doing that.

 

[CJVx]

@CJVx , Does the sub look like this?
View attachment 1351683

And does the waveform look like this?
View attachment 1351689

If so, I had luck by cleaning all the pots and then hitting the solder joints on them.

Note that these subs were never designed to have a continuous sine wave run through them. I blew the fuse on this one doing that.

Yes it is a very similar model, and the wave looks very similar to yours. It’s a bit dirtyer though. Thanks for the tip, I’ll defilitely check out the pots, thanks for the info, I’m excited to try!

 

[toddalin]

If you get it working properly again, pull the amp out of the cabinet and put it in its own cabinet and make a block-off plate for the speaker. These literally shake themselves to death and I did this after having mine repaired twice, first by Sunfire then by Rita's. (Rita was an employee there.) Haven't had a problem since.

 

[onwardjames]

T'was some guy on ebay selling those for absurdly low prices about a year ago.

I almost pulled the trigger, but I am no tech, so I didn't.

Wicked little bitches when they work.

 

[CJVx]

Well I checked out the pots, resoldered and cleaned, torqued down the nuts, but my symptoms remain. Slightly different than Rays, my clip on the bottom isn’t as apparent, plus now the crossover distortion is gone with some careful adjustment of what I think is the idle current pot. Here is the output of a 20Hz sine wave. Also, if I switch it to a square or triangle wave input, the output still looks similar to a clipped sine wave as shown.