Need help to repair two phase 400 amps

laatsch55

laatsch55

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Goin to bed. Gotta be outta the house by 5am. Good Nite....


In the meantime. Remount the caps, tape off the ends of all exposed wires off the boards. And build a cap discharger , consisting of a 50 to 100 ohm, 5 to 10 watt resistor with a 6" or so piece of wire soldered to each end, and then solder an alligator clip to each end. Then heatshrink or tape any exposed wire on that assembly.

See ya tomorrow....
 
LarryD

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laatsch55 said:
Goin to bed. Gotta be outta the house by 5am. Good Nite....


In the meantime. Remount the caps, tape off the ends of all exposed wires off the boards. And build a cap discharger , consisting of a 50 to 100 ohm, 5 to 10 watt resistor with a 6" or so piece of wire soldered to each end, and then solder an alligator clip to each end. Then heatshrink or tape any exposed wire on that assembly.

See ya tomorrow....
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I have to drive a good distance to purchase the resistor and clips . I will have it done the next time I log in.
 
LarryD

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laatsch55 said:
Lookin good Larry. Have you checked all your fuses??
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I just got back from a 44 mile drive to get the resistor. Radio shack did not have anything close! So I asked Siri for a fry's. The nearest fry's is 96 miles one way. So if it is needed for the test we will have to put it off. But if it were for my safety screw it, I will be carful.
 
laatsch55

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I'll send one with the care package, won't really need it till then...


Do a quick visual again to make sure no bare wires are hangin around and plug it in.....use the DBT the first time. Then we want to measure DC volts by putting the negative lead on the bus bar between the caps, and the red lead on the other cap terminal, one on each cap, one at a time....you should see 60 volts +(plus) on the cap terminal closest to the fuses and 60 volts DC- (minus) at the other cap terminal furthest from the fuses. That 60 figure should be 80 WITHOUT the DBT in line....
 
laatsch55

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LarryD said:
I just got back from a 44 mile drive to get the resistor. Radio shack did not have anything close! So I asked Siri for a fry's. The nearest fry's is 96 miles one way. So if it is needed for the test we will have to put it off. But if it were for my safety screw it, I will be carful.
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You can check voltage in the caps with your meter to see if it's safe to do any work in the chassis....
 
LarryD

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Lee, I wanted to check some components on the board because we did not find any problems with all of our other checks. Just to rule out any possible screw ups on my checking. The last thing I want to do is hurt the new board or outputs!
 
laatsch55

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That's what we are doing with the power supply checks.....but you can do what you want....it's your amp.....but you're chasing your tail until you know a little more. It is a good way to gain experience in testing components, but once again, I don't remember which component has to be out of circuit without checking a good PL14 board right along with you and I don't have the time for that right now. I can tell you that all transistors can be checked on the board for shorts and opens, but not all for reverse biased operation, so you can weed out the more obvious problems. On those that get a reading in reverse bias mode you will have to pull and test, and by reverse bias I mean putting negative on the base on an NPN, or positive on base on a PNP. You also need to download data sheets for each transistor on the board to get the pinouts or study the schematic for each one. The transistor symbol gives plenty of cues for NPN, or PNP identification, and then by comparing which components connect to each lead you can identify pinouts.

Read this post twice before replying....it really does make sense, and I'm not saying I won't help with the board, but I do have 6 amps sitting here that I need to get done too..so it might be awhile before I can pull out an old PL 14 and give you a definitive answer, and that's if the one I have has a similiar failure mode ( there's always that to consider too, when comparing board readings is mine as F*&^%$# up as yours is)....
 
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