Richard's PL Beastie Rework

Gepetto

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jbeckva said:
Well.... (gulp).... folks we had an "incident" tonight.... And JOE.. dagnabit.... you're like the "Prophet of PLWO" sometimes. You had some reservations on those 100V caps, and seeing as how this guy's been "clocked" at close to 108 yup.... :banghead:

(sad story to follow)...

So there I was... just chilling with the amp on.. barely anything... and then I hear my UPS "click" and hear this funny sound from it at the same time. Music was still going... hmmm.. wtf? Then my UPS pops up that warning.... "you have overloaded your UPS"...

OH SHIT

As soon as I hit the power on the amp, PWOOOOOOSSSSHHHHH!!! I hear something like a steam valve go off.. then all this nasty ass smoke pours out of the top. FWUUUUUCK!

Get it apart... one of the cap's spooged a good amount of electrolyte, and man .. it's HOT AS HELL...

DAMN DAMN DAMN.. Well Richard, it was good it was still here! But we're looking at new caps again. I'll take the hit for that.

BUT... I think guys I'm going to have to go with what I can get, and also NOT put anything in this "hottie" below 150 wvdc! Can't take that chance.

I see 11,000 uF's available right now that are 150V and will fit. Think that ought to be "enough" guys? Again, I can't take the chance of this happening again. I probably should replace the BR for good measure, too.

(dang... yep Lee... we gotta "keep em" for a week or so sometimes, eh??)
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I hate being that kind of prophet Jer. Hope you did not ruin too much stuff inside the amp when it spewed on you. It is always good to do the forming/leakage test at higher than the application voltage to ensure that the caps do not have a runaway problem.
 
NavLinear

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Gepetto said:
I hate being that kind of prophet Jer. Hope you did not ruin too much stuff inside the amp when it spewed on you. It is always good to do the forming/leakage test at higher than the application voltage to ensure that the caps do not have a runaway problem.
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Joe,

Is it ok to run electrolytic capacitors with a voltage rating of 100 V in this application? It seems that the voltage is less than 10% greater than the max voltage specified. Most of my experience was with Mil-Spec components and now with industrial grade hardware so this is still a little foreign to me - (commercial components).
 
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NavLinear said:
Joe,

Is it ok to run electrolytic capacitors with a voltage rating of 100 V in this application? It seems that the voltage is less than 10% greater than the max voltage specified. Most of my experience was with Mil-Spec components and now with industrial grade hardware so this is still a little foreign to me - (commercial components).
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Not really Dennis. Electrolytics should be derated by 20% from their rated voltage. Phase got away with it but they probably told GE, CDE and Sangamo that they would be running them at 100V so they manufactured them to that C-V formula. 9800uF is not exactly a household capacitance rating after all (nor is 5900uF at 85V).

Caps in this application should really be rated for 125V or higher...
 
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laatsch55 said:
Why derated Joe?? Surges??
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De-rating is always done for reliability purposes Lee. The percentage de-rating varies depending on component type. When you work in high-rel electronic applications as Dennis and I do, it is common practice.
 
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Joe, I have some Holden and Fischer toroids and don't know the secondary amp rating. How do I determine that??
 
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Without knowing the design specs Lee it is not straightforward. Can be approximated by measurement.

Can you measure the size of the secondary wire to determine the wire gauge? That is one important parameter.

Put an AC current probe in the primary and load the secondary with a resistive load. You should see a nice sine wave current on the primary. Increase the secondary resistive load until you start to see a distorted current waveform on primary, this will tell you where core saturation is starting to occur. Core saturation = bad. Measure the secondary AC voltage and figure the AC secondary current by dividing the voltage by the resistive load on it. Now you have the saturation current, multiply it by 0.8 to get a safe operating maximum current.
 
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Isolate the scope first--correct? And my 2,000 watt load bank should do, I can go from 4 ohms to 16.
 
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If wire on secondary is only 22 AWG, that is not much current capability on the output. I^2*R losses will cause heating effects in the core and windings. Would guess 2-3A based on the wire size.
 
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In any case, I'll have two 150V rated caps in my hands probably by weds this week. Even at 11K instead of the 22K's I've been used to using, it's the hope that we still have enough reserve to make the build "WOPL Worthy". I think it will... but yeah, kind of a gamble here.

BUT.. if it turns out good, then at least I know (a) I have caps in there rated ABOVE the average 700's rail voltages and (b) Where to get 'em "new" and "guaranteed".
 
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jbeckva said:
In any case, I'll have two 150V rated caps in my hands probably by weds this week. Even at 11K instead of the 22K's I've been used to using, it's the hope that we still have enough reserve to make the build "WOPL Worthy". I think it will... but yeah, kind of a gamble here.

BUT.. if it turns out good, then at least I know (a) I have caps in there rated ABOVE the average 700's rail voltages and (b) Where to get 'em "new" and "guaranteed".
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Wish they weren't so expensive but at least they are properly rated for the task.
 
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Ok, they're in and the beast has survived what amounts to a heart and lung transplant, heheh.

Listening now... still a whole lotta power as far as I can tell. Obviously I can't make a conclusion yet til we REALLY get some ampin' going on in here, but it's past midnight... and I'd wake the dead (and the she-bear, which wouldn't be a good thing... :angryfire:)

Whew... glad the cap blow didn't take anything with it.. and we gots a good 40+ volts of rated headroom over the 107.6 this guys putting out on the rails. Will be torturing it (and the neighbors.. and the dogz... and the catz... and the she-bearz...) this weekend again. :thumbright:
 
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