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PPX failure

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GAZ. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GAZ. Quote  Post ReplyReply Direct Link To This Post Topic: PPX failure
    Posted: 15 April 2018 at 9:47am
For the first time ever, had one of my PPX go down last night. 1600 on bass. Lost one channel, clip light constantly lit. Fearing the worst swapped a cable and ran both subs off the one channel. Carried on for about 30 seconds more then click! No more bass. Both clip lights lit. Could smell something was hot so had a look with a torch and saw the fan wasn’t working and realised it had overheated and cut out. Managed to get a desk fan, gaffa taped that round the front of the amp rack. Felt like the heat from a P3000 out the back! Left it for 5 minutes, switched it back on and away it went again! Carried on all night like that no problem! you can depend on your PPX that’s for sure!
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djeddie View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote djeddie Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2018 at 2:53pm
Thermal switches! Also, while you've got the top off to fit the thermals, check the caps for bulging. Had a 1200 that did that and it kind of roasted them!
Chas n Dave : it's like Drum and Bass but with beards.             E=mc² ±3dB
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dub Specialist Sound Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2018 at 4:04pm
Wow Gaz

just shows ya man , real amps lol
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GAZ. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GAZ. Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2018 at 4:29pm
Yeah I’m expecting the thermal switches. Undecided about replacing them or just re wiring the fan to run constantly.
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GAZ. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GAZ. Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2018 at 4:36pm
Definitely. I can’t see any of these modern amps still going in the future like a PPX does.
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jammin75 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jammin75 Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2018 at 5:09pm
shud carry an inuke 6000 put that in front of your amprack and that will keep it cool  LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2018 at 12:28pm
Probably best to wire the fan permantly on as it's a 1600 Gaz, you wont get the same problem again. Get really hot these 1600's. It wont do it any harm having the fan on continuely.
Be seeing you.
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GAZ. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GAZ. Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2018 at 2:23pm
Got another problem with the same PPX now
Switch on no problem works for a few minute then trips the breaker.
Still trips with the channel pcb's disconnected. So I'm guessing I've got a problem with one of the toroidals leaking to earth intermittently. Anyone had this problem before? I'm going to have a better look at it shortly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2018 at 6:05pm
Problem could still be a faulty rectifier or a smoothing capacitor.

Disconnect the transformers AC secondary cables from both bridge rectifiers, if the problem goes then it's a rectifier / cap problem if it's still there then this confirms a transformer fault / short on one or both transformers.

Wink


Edited by simonp1100 - 29 April 2018 at 6:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2018 at 6:40pm
Gaz, is the fan actually working now? From memory, the pair of transfomers,one has a 115v tap that feeds the fan,just check to make sure it has voltage ( see if you have voltage at the thermal switches) ,and is not snagged/shorted somewhere. There is also a thermal trip built into the top of the torrids,this may be faulty on one of them.  Will a bit of elimination you should be able to sort it ok.
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GAZ. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GAZ. Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2018 at 8:25pm
Think I might have the problem, looks like it’s the fan. The amp ran ok last gig when the fan wasn’t working so I thought I’d try that first and disconnected it, (fan rewired to run constantly since previous failure) then the power supply ran the rest of the afternoon no problem (pcb’s unplugged so they didn’t overheat) whereas before it would only run briefly before tripping the RCD. It appears it’s a mains fan rather than than fed via the transformer.

Edited by GAZ. - 29 April 2018 at 8:33pm
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jbl_man View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2018 at 9:04pm
Glad you found it, i could have sworn it was a 115v fan, will check the schematic.

Yup,you are right,seems to be a mains fan,it's connected just after that big 50w soft-start resistor.


Edited by jbl_man - 29 April 2018 at 9:15pm
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