Looking for info on Ampeg B4

[MarkusBass]

I'm looking for info about Ampeg B4 bass amp - the old version, not the new one B4R. I need schematic and information on power handling. I've got one here with a complain that it looses power when used in a bridge mode. Each of the power amps uses 4 pairs of IRFP240/9240. In stereo mode I can get 38V@4 Ohms, and in bridge mode I get 76V@8 Ohms. It seems to me that this are reasonable figures. And I doubt that with only 4 pair of MOSFETs the amp can be used @2 Ohms stereo and @4 Ohms mono. I cannot test the amp for a longer period of time because I don't have a dummy load that could handle such power. Within 2-3 minutes nothing wrong happens.

Mark

[Jazz P Bass]

This is all that I could find.
"the amp is rated rms power ouput (2ohms) 500-watts x2
(4ohms) 340-watts x2/1000 watt
(8ohms) 205-watt x2/700 watt mono"
76 volts at 8 ohms sounds correct.

[MarkusBass]

Thanks,

This is exactly what I've seen. I get 340Wx2@4Ohms and 700W@8Ohms mono. The main question is whether the amp can work @2 Ohms stereo, or @4 Ohms mono. Looking at 4 pairs of MOSFETs I doubt it. The owner of the amp tries to run it @4 Ohms in bridged mode.

Mark