Hi folks!
I have Peavey PV 1500 that has an unusual problem on the "b" channel.
after about 7-10 secs.after shutdown it makes a "burping or farting"noise for about a sec or two
.other than that,it runs fine.If this helps,i had replaced the "a"channel board that was blown to bits with a brand new one from Peavey.I have the schematics here but i don't know what i'm looking for.Maybe the muting circuit or bad caps? I don't work on these to often.
Thank in advance.
I have Peavey PV 1500 that has an unusual problem on the "b" channel.
after about 7-10 secs.after shutdown it makes a "burping or farting"noise for about a sec or two
.other than that,it runs fine.If this helps,i had replaced the "a"channel board that was blown to bits with a brand new one from Peavey.I have the schematics here but i don't know what i'm looking for.Maybe the muting circuit or bad caps? I don't work on these to often.Thank in advance.
I'm not going to download this schematic but I have a PV2000 one. There is a 2.2 uf cap to the gate of the Jfet, the J174. I'd start by replacing that. Polyester will probably fit, look at the dimensions. Then that would last forever.
This is old enough all those little electrolytics are suspicious. If you buy 10000 hour service life rated ones from newark or digikey, you might not have to do this again for 10 years. 22 uf up you have to go electrolytic. Don't forget the non-polar cap on the input board, could go polyester too.
Also your mains caps probably are restricting your output power by this time with high ESR. 3000 hours is about the best I can find. No, you can only buy 4 post from Peavey, I use 3M windshield adhesive to glue them down. Make sure the mains are short enough. If you buy e-caps all in one order, the $8 freight bill is not so bad.
Clean the heat sink & fan while you're in there. I cut a filter & put over the inlet grill on my units, after replacing the output transistors blown by too much dirt on the sink. Tie wraps to the grill work.
This is old enough all those little electrolytics are suspicious. If you buy 10000 hour service life rated ones from newark or digikey, you might not have to do this again for 10 years. 22 uf up you have to go electrolytic. Don't forget the non-polar cap on the input board, could go polyester too.
Also your mains caps probably are restricting your output power by this time with high ESR. 3000 hours is about the best I can find. No, you can only buy 4 post from Peavey, I use 3M windshield adhesive to glue them down. Make sure the mains are short enough. If you buy e-caps all in one order, the $8 freight bill is not so bad.
Clean the heat sink & fan while you're in there. I cut a filter & put over the inlet grill on my units, after replacing the output transistors blown by too much dirt on the sink. Tie wraps to the grill work.
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Thanks for the feedback indianajo! Here's the schematic if your interested. I put a DVM on the B speaker output after shutting it down and at about 4 secs the voltage ramped up to about 1.7 volts then finally bled back down. Looks like i'll be placing an cap order with Mouser! I wonder if when the A channel PCB self destructed,it sent a surge or spike into the B channel? Hopefully not!
View attachment peavey_pv-1500.pdf
View attachment peavey_pv-1500.pdf
Your DC spike is probably just old age caps. At least they are guarenteed to be **** at this age. Bad connections like in the Peavey used punchdown blocks interboard can also cause problems, don't hesitate to remove & replace, especially on low voltage circuits like the flying ground.
What I don't like about mouser is they make you download all the cap datasheets and read them to find out what service life cap you are buying. And on the same datasheet different size caps have different service lives. All the top grade suppliers like panasonic, nichicon, rubicon, vishay, make 500 hour caps for prototypes that are going to be discarded in 3 months. Also repair shops that want the customer to come back with the same problem in one year.
Digikey & newark have the cap service life in the selector table. I like 10000 hours, but can only get 3000 hours in caps >= 1000 uf. I've done the mains cap in my ST70 4 times in 49 years. Life is too short to do stuff over & over again. I had to buy **** grade in TV repair shops the first 3 times, now we have the internet & debit cards so newark will actually sell to me.
What I don't like about mouser is they make you download all the cap datasheets and read them to find out what service life cap you are buying. And on the same datasheet different size caps have different service lives. All the top grade suppliers like panasonic, nichicon, rubicon, vishay, make 500 hour caps for prototypes that are going to be discarded in 3 months. Also repair shops that want the customer to come back with the same problem in one year.
Digikey & newark have the cap service life in the selector table. I like 10000 hours, but can only get 3000 hours in caps >= 1000 uf. I've done the mains cap in my ST70 4 times in 49 years. Life is too short to do stuff over & over again. I had to buy **** grade in TV repair shops the first 3 times, now we have the internet & debit cards so newark will actually sell to me.
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Good morning all!
I apologize for such a long delay,but life gets in the away quite often around here lately.. But the good news is that the channel b board is fixed! It was a small electrolytic cap with a bad solder joint! I decided to recap both boards with better quality caps and sounds great! The thing that concerns me is that the replacment board from Peavey i which believe is for a Crest cpx 1500! This board uses a daughter card with a different ic for the DDT circuit and a different value bipolar cap in the protection crowbar circuit.(2.2 uf cap on the original Peavey board as opposed to a 10 uf on the replacement board. This is from the Crest schematics i downloaded. It also answered a niggling question about a mod on the b board that appears to be for the bias circuit.I want to try this amp on a pair of AR9's but i'm kinda on the fence about trying it as they're known amp killers. Thanks for the help so far!
I apologize for such a long delay,but life gets in the away quite often around here lately.
. But the good news is that the channel b board is fixed! It was a small electrolytic cap with a bad solder joint! I decided to recap both boards with better quality caps and sounds great! The thing that concerns me is that the replacment board from Peavey i which believe is for a Crest cpx 1500! This board uses a daughter card with a different ic for the DDT circuit and a different value bipolar cap in the protection crowbar circuit.(2.2 uf cap on the original Peavey board as opposed to a 10 uf on the replacement board. This is from the Crest schematics i downloaded. It also answered a niggling question about a mod on the b board that appears to be for the bias circuit.I want to try this amp on a pair of AR9's but i'm kinda on the fence about trying it as they're known amp killers. Thanks for the help so far!
Another poster with as much persistance as I. Congratulations. Lucky the bad solder joint was on a doomed to fail anyway e-cap. Peavey in the 90's were hand soldered, which led to good looking joints that only worked sometimes. Takes patience to find them. 4 techs had been in my PV-1.3k, had given up and put "do not use channel A" label on it. Bad solder joint on the feedback pin of the gain op amp.
The ability to make 50 v whoops when a RCA plug falls out of the adapter is one reason I leave my PV-1.3K in the attic. The speakers might stand that, maybe. Since the speakers cost 6x what the amp did, and will never be that cheap again, I went and found a PV-4c for $28 on ebay. That one only needed output transistors & rail caps, some times you luck out.
Peavey did improve the DDT circuit as time went on, IMHO. Newer faster parts became available, the J174 and 3180 became odd and expensive as manufacturers dropped them. J174 is back in production again but $2 now, not $.33.
If the R*C time constant of the protection crowbar is the same, I wouldn't worry about it. What I worry about is the triac melting the lands off the board (as mine did) instead of tripping the main breaker. I've designed a rail cap disconnect circuit for the PV-1.3k using nfets, but never installed it because it is a bit to large to squeeze in. If I ever get popular enough to play audiences of 300, I'll put the PV-1.3k on the front burner. Right now I play for 10 people, on wood piano, no amp required.
Modern (MJ21193/4) $4 output transistors make the bias current different than the OEM $5 apiece MJ15024/25. So I modded my bias current circuit, too. Check the value, 20-40 ma apiece should be good. Actually I think only one pair needs to have idle bias current, but measuring all 8 or 10 is such a P***. Nobody on here will give me a straight opinion about letting the other 3 or 4 pairs run class B, only one pair is class AB. Since buying only 3 extra transistors leads to slightly mismatched Vbe transistors, only pitching out 3 of them. In small lots (not full rails of 25 each) I get a lot of transistors made on different days. Peavey bought lots of thousands and could match transistors extremely closely using a machine, I imagine.
Happy diyaudio.
The ability to make 50 v whoops when a RCA plug falls out of the adapter is one reason I leave my PV-1.3K in the attic. The speakers might stand that, maybe. Since the speakers cost 6x what the amp did, and will never be that cheap again, I went and found a PV-4c for $28 on ebay. That one only needed output transistors & rail caps, some times you luck out.
Peavey did improve the DDT circuit as time went on, IMHO. Newer faster parts became available, the J174 and 3180 became odd and expensive as manufacturers dropped them. J174 is back in production again but $2 now, not $.33.
If the R*C time constant of the protection crowbar is the same, I wouldn't worry about it. What I worry about is the triac melting the lands off the board (as mine did) instead of tripping the main breaker. I've designed a rail cap disconnect circuit for the PV-1.3k using nfets, but never installed it because it is a bit to large to squeeze in. If I ever get popular enough to play audiences of 300, I'll put the PV-1.3k on the front burner. Right now I play for 10 people, on wood piano, no amp required.
Modern (MJ21193/4) $4 output transistors make the bias current different than the OEM $5 apiece MJ15024/25. So I modded my bias current circuit, too. Check the value, 20-40 ma apiece should be good. Actually I think only one pair needs to have idle bias current, but measuring all 8 or 10 is such a P***. Nobody on here will give me a straight opinion about letting the other 3 or 4 pairs run class B, only one pair is class AB. Since buying only 3 extra transistors leads to slightly mismatched Vbe transistors, only pitching out 3 of them. In small lots (not full rails of 25 each) I get a lot of transistors made on different days. Peavey bought lots of thousands and could match transistors extremely closely using a machine, I imagine.
Happy diyaudio.
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Thanks indianajo!
I wonder if i should change the 2.2 uf's to 10uf's? I had already had the parts on hand before i found this discrepancy,so i changed the 10uf to the 2.2uf so that they were both equal.Do you think that was a mistake? I probably call Peavey about the DDT daughter card tomorrow. Both ic's are considered obsolete now.
The AR9's are capable of dipping below 2 ohms,that's why i'm concerned about the crowbar circuit. It's also interesting that crest used 1n4007 diodes in the -15v/
+15 power supply.
I wonder if i should change the 2.2 uf's to 10uf's? I had already had the parts on hand before i found this discrepancy,so i changed the 10uf to the 2.2uf so that they were both equal.Do you think that was a mistake? I probably call Peavey about the DDT daughter card tomorrow. Both ic's are considered obsolete now.
The AR9's are capable of dipping below 2 ohms,that's why i'm concerned about the crowbar circuit. It's also interesting that crest used 1n4007 diodes in the -15v/
+15 power supply.
Just check that the r*c time constant of both boards is 0.1 second. as 47k * 2.2 uf (microfarad, 10tominus6th) is 0.1 second.
The AR9 2 ohms shouldn't interact with the crowbar circuit. The crowbar circuit looks for 8 v dc ( value of the sbs) on speaker for 0.1 second then trips the short to blow the mains fuse. That might have been a bit too sensitive, I'd probably set crowbar trip for a quarter or half a second or so of DC.
What you should worry about on AR9 is a big burp of AC blowing the tweeter sky high. AR speaker should not have tweeter protection in it - it wasn't invented yet before AR was bankrupt. If you can get in the speaker, put a 25 v or so bidirectional protection diode (tvs) across the tweeter behind a fast blow fuse. A PTCR self reset "fuse" instead of meltout type could prevent you from having to open the box again. Those reset when power is turned off and they cool down.
Peavey.com has a forum, maybe the answer to your question has been posted on there already.
The AR9 2 ohms shouldn't interact with the crowbar circuit. The crowbar circuit looks for 8 v dc ( value of the sbs) on speaker for 0.1 second then trips the short to blow the mains fuse. That might have been a bit too sensitive, I'd probably set crowbar trip for a quarter or half a second or so of DC.
What you should worry about on AR9 is a big burp of AC blowing the tweeter sky high. AR speaker should not have tweeter protection in it - it wasn't invented yet before AR was bankrupt. If you can get in the speaker, put a 25 v or so bidirectional protection diode (tvs) across the tweeter behind a fast blow fuse. A PTCR self reset "fuse" instead of meltout type could prevent you from having to open the box again. Those reset when power is turned off and they cool down.
Peavey.com has a forum, maybe the answer to your question has been posted on there already.
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