PV 1.3K won't drive 2 ohms with DDT on

[booj]

Working on a PV 1.3k that works perfectly except that apparently, the DDT circuit prevents full output into 2 ohms. It doesn’t want to put out more than 20 volts at that load. With the DDT off, all is fine. If you happen to know something about this circuit. (I can't find it on the scat) like where it is in the amp, I would very much appreciate hearing from youPeavey-PV1.3K amp.pdf

[Steve Conner]

The DDT circuit detects distortion in the power amp and reduces the gain until it goes away. So probably something is wrong with the power amp causing excessive distortion when driving a 2 ohm load, and the DDT is just doing its job.

Are all of the output transistors functioning? Check for loose wires, bad solder joints on the output PCB, blown emitter ballast resistors, and the like.

IIRC, the DDT circuit is based around a CA3080 voltage controlled amplifier chip, except it appears on the schematic under Peavey's house part number.

[J M Fahey]

What do you mean by

won't drive 2 ohms

?
2 ohms per channel or 2 ohms mono bridged?
Not the same.

[soundguruman]

Don't load a solid state amp with 2 ohms.
Manufacturers rate them at 2 ohms, but they won't last. They get too hot.
Call the PV service department and ask for all the service notes on that amplifier.

No, not 2 ohms bridged. 8 ohms bridged.

The DDT turns on because the amp has reached the current limit. The output is overloaded.

[booj]

Thankyou very much for your responses guys! I meant 2 ohms per side, not bridged. Steve, I should have remembered about the CA3080, or would it be the CA-3094 / 70487478? Anyway the thing looks out of the box new. I'll continue the search.

[soundguruman]

Working on a PV 1.3k that works perfectly except that apparently, the DDT circuit prevents full output into 2 ohms. It doesn’t want to put out more than 20 volts at that load. With the DDT off, all is fine. If you happen to know something about this circuit. (I can't find it on the scat) like where it is in the amp, I would very much appreciate hearing from you[ATTACH]20706[/ATTACH]

There may be a substitute circuit for the DDT
CALL the PV parts department.
601 483 5365
On some models they changed that DDT to a different part.

[booj]

Problem solved. The AC plug blades were pinched too tightly together. I spread them apart with a sharp kinife for better contact with the outlet. Puts out full power with the DDT on at 2 ohms each channel.

[Jazz P Bass]

Get the heck out!

[g1]

I've heard of stranger things, but it makes no sense to me that the AC plug was only a problem if the DDT was on?

[Steve Conner]

Bear in mind the DDT probably triggers at distortion levels that aren't quite visible on a scope trace.

the argument goes something like this: Misshapen plug pins - high resistance - slight drop in line voltage to amp - premature clipping - DDT kicks in.

If the plug pins happened to be sparking, the electrical noise from that could maybe trigger the DDT too.

[Steve Conner]

Bear in mind the DDT probably triggers at distortion levels that aren't quite visible on a scope trace.

the argument goes something like this: Misshapen plug pins - high resistance - slight drop in line voltage to amp - premature clipping - DDT kicks in.

If the plug pins happened to be sparking, the electrical noise from that could maybe trigger the DDT too.