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Peavey pv1500 weird noise after shutdown on channel b
Peavey pv1500 weird noise after shutdown on channel b
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Old 26th June 2019, 03:10 AM   #1
mrflex65 is offline mrflex65  United States
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Default Peavey pv1500 weird noise after shutdown on channel b

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.
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Old 26th June 2019, 01:22 PM   #2
indianajo is offline indianajo  United States
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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.
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Last edited by indianajo; 26th June 2019 at 01:33 PM.
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Old 27th June 2019, 03:11 AM   #3
mrflex65 is offline mrflex65  United States
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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!


peavey_pv-1500.pdf
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Old 3rd July 2019, 02:21 AM   #4
indianajo is offline indianajo  United States
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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.
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Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 3rd July 2019 at 02:24 AM.
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