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Old 4th March 2013, 07:38 PM   #11
Enzo is offline Enzo  United States
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I am assuming that is a Peavey PV900 amp. It shares the schematic with the PV1500. COntact them - customerservice@peavey.com - and ask for the schemtic.

Is there a second one of these parts right next to the bad one, called R2?

Schematic identifies them as a 1 ohm 30A for 120v mains and 2 ohm 15A for 240v mains. The 1 ohm 30A one has a Peavey part number of 70250123, and I am sure they could provide the number for the other one.

If you are in the USA, you can call Peavey and order th exact part direct from them at a reasonable cost. Otherwise any inrush limiting thermistor of similar characteristics will work.
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Old 4th March 2013, 08:01 PM   #12
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To me,it looks like it says "1R030". Which makes sense,considering what Enzo says above (1ohm,30A)
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Old 6th March 2013, 01:12 AM   #13
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thanks DF96 for the suggestion. Built one tonight and about to see what happens.

DigitalJunkie and ENZO seem to be right about the part being the 1R030. It's just really hard to read but I'll look into getting that schematic. On the PV900 the R2 insert on the cb is just bridged with no thermistor in that spot.

Thanks for all the help. Even if I don't get it going, I'm learning a good bit. I'll post a pic of the lamp test.
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Old 6th March 2013, 02:39 AM   #14
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Default lamp test and toroidal transformer

so I hooked the lamp test directly to the transformer.
(pics wouldn't upload for some reason)

the bulb stayed off and it was definitely getting voltage, no over heating no funky smell, nothing but measured voltage at 117.8

I'm planning on ordering the thermistor (or 2 or 3) and putting everything back together then run the lamp test. If it fails then (most likely it will) I suppose it's probably toast without a new circuit board.

history to this point: I had to remove the transformer to check out the damage. Wire leads were melted to the copper. dug these out and temporarily taped so there was no contact. (It's lame but I was just planning on butt splicing it back into the board instead of fooling with resoldering everything to find out it still doesn't work) removed circuit board and repaired small short with a wire bridged (learned solder doesn't stick to plastic, duh) hooked it back up and it seemed to work for a few seconds and then breaker on amp tripped. Tried it one more time, because I'm brilliant, and saw the heat fry through this thermistor and crack it.
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Old 6th March 2013, 03:04 AM   #15
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ah, here we are, some pics. I see that in some cases smaller is better
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Old 6th March 2013, 07:08 PM   #16
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Well, the thermistor is there to sort of gently let things warm up (it is still pretty quick though) instead of having this massive blob of voltage go through to your transformer and parts downstream. You might be able to use it without a thermistor to see if the amp is going or not as the value of the resistance goes down dramatically as the thermistor heats up.

Other than that, wow, did the transformer look like that before or after the incident?
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Old 6th March 2013, 07:12 PM   #17
Enzo is offline Enzo  United States
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It is a power amp, and when fuses or breakers blow, or inrush limiters burn, by far the most common reason is a blown amp channel, and that means shorted output transistors. Check your outputs for shorted condition.
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Old 7th March 2013, 01:29 PM   #18
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great, thanks for the tips. The transformer came with some serious tape melting and I removed about half of it to get access and see if it had a short. Unfortunately, the center of that trans is filled with epoxy and a metal tube to receive the bolt through. The trans could still be shorted but the lamp test did not reveal that.
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Old 7th March 2013, 01:45 PM   #19
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The transformer came looking like that before the blow up? Wow... I have touched many a toroidal transformer and they most of the time run much cooler than the big iron. I am sure you have checked it properly and been very careful about it, but the possibility of an intermittent short? Who knows? I would be careful.

Check the outputs for a short like Enzo recommends. If this doesn't happen to be the case and none are found then take care with that transformer.

One doesn't usually see that in a normal working transformer (Chinese or Canadian made). How much would it cost to replace a like transformer from Piltron or going with big iron from Edcor USA or Lundahl in Europe?
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Old 7th March 2013, 01:55 PM   #20
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I'd be into replacing it if it's not crazy expensive. I haven't been able to find one like this one but I don't know the exact specs but I'm hoping it'll be in the schematics. I'll check the companies you mentioned and see what the cost is.

I ordered a new thermistor.
Then I suppose I'll figure out how to test outputs with Speakon connectors.

After that it's the scrap heap.
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