I have a PV1500 that has been messed with after a child stuck pennies in vent slots in back of amp, shorted across two adjoining wire jumpers some traces have been damaged and I suspect the 3 legged critters close by have been damaged that being said I repaired jumpers (not on schematic) and powered up with light bulb and variac. R234 gets real hot and r235 gets hot q203,205and 207 all are hotter than everything else Q207 is on heatsink. I suspect an output or 4 are shorted nothing on the speaker jacks as I suspect its in protection mode ...I'm attempting to post schematic.
This amp has a similar design philosophy to the PV-1.3k I have repaired, but different output transistors and crowbar components. If your amp does not blow the breaker with DC on the output, then the protection components are not working, as they didn't in my amp. My amp crowbar (SCR) melted the traces off the circuit board instead of blowing the breaker like it is supposed to. Twice, once while I was looking at it.
I find the double diode DVM test can find totally shorted output transistors, but they keep blowing up at rail voltage unless you perform a better test for damaged ones. I put a capacitor across the output of a car battery charger to produce 17 VDC. I put a 47k resistor in series with it. Then I rigged the power supply in series with the 2 ma scale of a DVM, to test current flow backwards against 17 VDC. I short the base to emitter then put plus to collector on the NPN's, and minus to collector on the PNP's. Eliminating the transistors that leak more than new ones, stopped the OT blowing up problem. I was able to reuse some Output Transistors in the driver position.
If your SCR is not blown up, disconnect the SCR's from the trigger MAC224 while testing. I used 5 ohms at 225 watts for an output test, paralleled with a 4 ohm car speaker protected from DC by back to back 4700 uf 100 V capacitors. My amp had a problem with a solder joint on the input op amp, that kept whanging it to 160 VDC on output if I touched the wrong thing. The car speaker would sound funny when this happened, saved me from having to measure output DC all the time.
Your SCR trigger may be blown up too, one of mine was. I found driver transistors blown, the limiters blown (Q102,103), the sense resistors and many emitter resistors blown, the 3080's blown, one of the input op amps blown, lots of blown diodes and 50 v capacitors and a few other resistors. I replaced 113 parts, total cost under $100, mostly for output transistors. I replaced every electrolytic cap also for that price, 1994 was too long ago.
I found 2SC5200 quite pricey at newark and 2sa1943 not available, the CA3080 available only at jameco, and the j174's just went unavailable at newark also. Peavey itself is probably the best source for parts, but I never used them because they respond best to telephone calls, and I don't have long distance service. The amp doesn't seem sensitive to alternate transistors, I used MPS8099-98 for Q102-103, different output transistors (all of them, not just some) different driver transistors, etc etc. Check the double diode temp sensor, one of mine was blown, and another Peavey only part. Edit you are in luck, your temp sense is common 1n4148, and you have a idle current set pot, which is something I'm having to rig up. Mine shows no idle current cold right now.
Do read the high voltage sticky on tube amp forum about safety around high voltage; with the flying ground this amp could be quite dangerous to newbies if you wear jewelry or use two hands making power on measurements. Wear safety glasses at turn on, exploding output transistors sometimes blow a die up to the ceiling. Mine went through the steel case of the TO3 package.
Good luck. I found fixing mine a fun puzzle. I'm putting in a FET speaker disconnect "relay" in mine now instead of the useless SCR crowbar. I'm reusing the Peavey DC fault circuit.
I find the double diode DVM test can find totally shorted output transistors, but they keep blowing up at rail voltage unless you perform a better test for damaged ones. I put a capacitor across the output of a car battery charger to produce 17 VDC. I put a 47k resistor in series with it. Then I rigged the power supply in series with the 2 ma scale of a DVM, to test current flow backwards against 17 VDC. I short the base to emitter then put plus to collector on the NPN's, and minus to collector on the PNP's. Eliminating the transistors that leak more than new ones, stopped the OT blowing up problem. I was able to reuse some Output Transistors in the driver position.
If your SCR is not blown up, disconnect the SCR's from the trigger MAC224 while testing. I used 5 ohms at 225 watts for an output test, paralleled with a 4 ohm car speaker protected from DC by back to back 4700 uf 100 V capacitors. My amp had a problem with a solder joint on the input op amp, that kept whanging it to 160 VDC on output if I touched the wrong thing. The car speaker would sound funny when this happened, saved me from having to measure output DC all the time.
Your SCR trigger may be blown up too, one of mine was. I found driver transistors blown, the limiters blown (Q102,103), the sense resistors and many emitter resistors blown, the 3080's blown, one of the input op amps blown, lots of blown diodes and 50 v capacitors and a few other resistors. I replaced 113 parts, total cost under $100, mostly for output transistors. I replaced every electrolytic cap also for that price, 1994 was too long ago.
I found 2SC5200 quite pricey at newark and 2sa1943 not available, the CA3080 available only at jameco, and the j174's just went unavailable at newark also. Peavey itself is probably the best source for parts, but I never used them because they respond best to telephone calls, and I don't have long distance service. The amp doesn't seem sensitive to alternate transistors, I used MPS8099-98 for Q102-103, different output transistors (all of them, not just some) different driver transistors, etc etc. Check the double diode temp sensor, one of mine was blown, and another Peavey only part. Edit you are in luck, your temp sense is common 1n4148, and you have a idle current set pot, which is something I'm having to rig up. Mine shows no idle current cold right now.
Do read the high voltage sticky on tube amp forum about safety around high voltage; with the flying ground this amp could be quite dangerous to newbies if you wear jewelry or use two hands making power on measurements. Wear safety glasses at turn on, exploding output transistors sometimes blow a die up to the ceiling. Mine went through the steel case of the TO3 package.
Good luck. I found fixing mine a fun puzzle. I'm putting in a FET speaker disconnect "relay" in mine now instead of the useless SCR crowbar. I'm reusing the Peavey DC fault circuit.
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Peavey has toll free phone numbers. You have to order by phone in the USA, parts emails are for information only.
I expect Peavey to have those transistors in stock, or reasonable substitutions. IT would be unusual for them not to have it covered.
Before you continue, measure with power off for resistance across the output of each channel - right at the speaker connections. If the channel output appears to be shorted, you probably have a shorted crowbar MAC224, CR228. Remove it if so, the amp will work without it during tests.
And DO NOT connect a speaker or load to the output until the amp is stable.
Note there are two sets of 15v rails. There are the dedicated regulated +/-15vg rails for general use in the amp, but each power amp section ALSO has its own pair of zener derived +/-15v rails. it is important they all be OK. CR215 CR224.
While you are at it, just check every darn diode on the channel. A bunch of them are involved in making bias for the later stages. Only takes a minute or so to do them all. And transistors, you have the six outputs, and only six more smaller ones. That is only 12 transistors, just check them all.
ANy transistor you discover to be shorted has a good possibility it damaged a resistor. Always check any resistors associated with dead transistors. And going the other way, any time you have a resistor getting real hot, look to the semiconductor that draws current through the resistor, probably faulty.
I expect Peavey to have those transistors in stock, or reasonable substitutions. IT would be unusual for them not to have it covered.
Before you continue, measure with power off for resistance across the output of each channel - right at the speaker connections. If the channel output appears to be shorted, you probably have a shorted crowbar MAC224, CR228. Remove it if so, the amp will work without it during tests.
And DO NOT connect a speaker or load to the output until the amp is stable.
Note there are two sets of 15v rails. There are the dedicated regulated +/-15vg rails for general use in the amp, but each power amp section ALSO has its own pair of zener derived +/-15v rails. it is important they all be OK. CR215 CR224.
While you are at it, just check every darn diode on the channel. A bunch of them are involved in making bias for the later stages. Only takes a minute or so to do them all. And transistors, you have the six outputs, and only six more smaller ones. That is only 12 transistors, just check them all.
ANy transistor you discover to be shorted has a good possibility it damaged a resistor. Always check any resistors associated with dead transistors. And going the other way, any time you have a resistor getting real hot, look to the semiconductor that draws current through the resistor, probably faulty.
Thanks for all the responses , Peavy cust svc was nice enough to send schematics to my email. Now to get down to work ...It may be a couple of days to get back to it as i have a Marshall amp on the bench and a headphone amp I'm working on. I will keep you all posted as I find all of the parts that the smoke got out of...
Regards , Elwood
Regards , Elwood
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