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prosigna 11th February 2019 05:48 PM

PV-1500 smoke and fire
 
I wired my Peavey PV-1500 into the sound system of the theatre at the local college to add my subs for a show. I placed the amp in the alcove with the rest of the theatre equipment and used the speaker cable patch panel to send the signal into the orchestra pit. The amp appears to have not liked that configuration. I was running bridge mono to a 1/4" cable. The patch panel for the speaker sends does not isolate the sleeve from the 1/4" jacks. All the -neg terminals are bound together. According to my meter - these -neg terminals bound to the patch panel are also grounded. So my amp was wired in - bridge mono - with the sleeve grounded. There is no way of knowing now which of the amp terminals was connected to the sleeve. I was using a banana-to-1/4" adapter but was not looking closely at which red was tip and which was sleeve.

The amp sat with no input waiting for me to get the rest of the system configured when I smelled smoke then saw fire. I am going from memory (the amp is back home) but it seems to have burned up R136 and R236.

What else would you check for before replacing these two resisters and testing?

Enzo 11th February 2019 07:48 PM

SO we ran the amp with a short across one of the channel outputs. I suspect it has blown your outputs.

Resistors never burn up on their own, so check any semiconductor associated with those resistors in any way. Look for shorted output transistors. Check the crowbar triac across the output for shorted.

prosigna 12th February 2019 12:01 AM

Whichever red post was linked to sleeve was run to earth ground. The other red post, which was linked to tip was open. Both boards show identical damage to R136, R137,and R139 (R236, R237, and R239). There does not seem to be any damage to the crowbar triac circuits - BUT - I have not removed the board and isolated any of the crowbay triac components NOR tested any of the diodes. This is just a preliminary list of obviously damaged components.

This amp has in the past shown small issues with a cold-solder joint type low-output until you really drive the input. I moved the amp from one location to another to do this installation. It is possible the failure was not due to the speaker patch panel. BTW There was no speaker connected to the other end of the line. It was an open circuit - other than the sleeves all having continuity to each other and earth ground.

prosigna 12th February 2019 12:50 AM

The circuit is open between the output terminals - does that mean the crowbar triac is not shorted?

Enzo 12th February 2019 02:03 AM

There is nothing in a circuit that will make a shorted triac appear not to be. Measure them right where they sit, They either appear shorted or not. If one DOES seem shorted, THEN remove it for further tests. They usually are gross failures, or they are good.

Please check your output transistors for shorts as well as the drivers. (Q106,107)


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