Tagged As: Peavey Power Amp
Question:
I run a professional amplifier service shop. I've seen most different topologies used for high power audio amplification. But, this Peavey amp really confuses me. It's a Peavey PV-1.3k massive 4U high stereo power amp. It came into my shop with one channel badly blown, looked like a disaster. 10pcs of blown output-devices, generally all emitter-resistors were open, pcb traces exploded, driver-board severly damaged. Customer refused repair and let me keep the unit for scrapping parts. As I really enjoy audio power amps I decided to repair it just for fun, in case I some day need 1000W per channel into 2 ohms. Said and done, all defective parts replaced, but I can't figure out how the stereo output-stage is configured. I'll try to explain it. The power-supply has dual centertapped secondaries, each channel uses its own supply of +/- 90V rails. The rails are applied to the output stage collectors like a standard emitter-follower output stage. Now the hocus pocus begins. Each output-device has its own pair of emitter-resistors connected to a COMMON rail on the output-board. This rail is actually used by both channels, so appearently both channels are in parallel. And this rail is connected to chassis ground. This rail is also connected to one side of the speaker output jacks. I haven't seen anything like this before. The other side of speaker output jacks goes straight to the centertap of the transformer. (channel power ground) These centertaps are not connected together. Most preferably, I would like to see the schematics for this amp, secondly, if anyone could tell me what's going on in this hocus pocus output stage.
Answer:
Obviously this would dump the rails directly to ground thru the output devices and the emitter resistors right? You must have made a mistake tracing this out, somebody rewired this incorrectly, or you are still measuring a short across the outputs. Are you familiar with a bridged output? That might be a bit confusing if you've never seen one before, but there still should be no path to ground from an output.
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