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Discussion Starter · #1 ·
My project for this weekend is going to be attempting to repair a PG-series power supply. I know all about the properiatery switching chips but I've also read a few people have found other problems in them. I have a basic electronics backround so I plan on checking all of the "normal" components first, resistors, diodes, caps, etc. I do have access to a high quality oscilloscope but I'm not sure what i'd check with it. I do also have the schematics and service manual.


Does anyone have any suggestions as to common repairable failures that I can check for, or other diagnosis suggestions?


Thanks,

Chris
 

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Is that a "GP" or "PG" power supply? BIG difference.


Marc
 

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I don't believe that the PG supply uses special chips like the GP. I have not had a failed PG supply, so I can't help you there. But at least it is repairable.


Marc
 

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I've got a PG6200 that I suspect may have a Power Supply problem. When I was trying to to fault find this projector (comes up with Fd error which is supposed to indicate HV problem) I did some measurements on the PSU that did not match what the Service Manual said. I imagine the PSU would be very similar although mine will be for 240V input. I'd be happy to do some comparative measurements, although as I say, I supect mine may be faulty. Mostly discreet components from what I could see, but wound components could be a problem for repair/replacement.

Mike
 

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When a local tech here back traced and compared a working HVPS from an NEC PG to one I had that didn't work, he found the following components blown and replaced them, they were between the main power input, and the first daughter board, and on the first daughter board. The were the 7watt 4.7ohm big white resistors, a zener diode just before the daughter board, and these parts as well, not totally sure where they were located as I'm going from the extra spare parts I have left over,4N35 LITEON N2 FD 6 leg IC(?maybe an OP AMP) a transistor, 2SK1512 7001 and a 16 pin Mitsubishi IC(maybe OP AMP), I'm not sure)A208000, M51977P. This last part was on the daughter board for sure, I remember. He had a real ***** of a time getting it off as it was 16 pins and soldered both sides. Hope this helps, its all I know about it.
 

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Discussion Starter · #7 ·
I thought the "special chip" applied to the PG ones as well... if not all the better then. If all of the components are available, then I should be able to track the problem down and repair it.


Paul, thanks for the information. This is the LV power supply I'm working on here, but I'm sure your information will be useful to someone later on, unless you made a typo and you were referring to the LV as well. This is the power supply from the "parts" unit I bought from you a few months back, btw. The other one is still running strong.


Mike,

Thanks for the offer of comparing measurements. I do however also have a working power supply in my main projector that I can pull out if I need to take measurements. If there's any measurements you need feel free to ask.


BTW, this failure in this power supply is no standby power. In case anyone's fought that battle before.


Any other comments welcomed... I'm going to be starting on this tomorrow morning; I'll be sure to post any successes, questions, or catastrophes.



Thanks,

Chris
 

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I mean the box under the lenses. The power supply which was repaired was the same condition, no standby power at all, seemed dead.


PS: AFAIK the specially manufactured transistor which fails in the GP series power supply is NOT used in the PG power supply. Currently AFAIK, the PG and XG power supplies are totally rebuildable.
 

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Thanks for the offer Chris. It will probably be some time before I get to look at the PG again, but I would like to get it going as it has half decent tubes. I working on my XG75 at the moment getting ceiling mount and HTPC sorted.


Mike
 

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Discussion Starter · #10 ·
Well so far I've found one of the large 4.7 ohm resistors blown, replaces that (jumpered actually) and got the standby power back, but I'm still not getting the projector to power up properly. When you hit the power button, the power light comes on but theres no other indication that the pj turns on. I then turns off after 2 seconds, then turns back "on" after a few more seconds, and cycles like this.


Unfortunately i'm in a little over my head now and I don't really have the electronics background (yet) to further diagnose this. I think I'm just going to hang onto the power supply for spare parts in case my good one blows.
 

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Check the items I said were blown on my power supply, they are between the resistor and the first daughter board. Perhaps they were blown in the same manner. The transistor is the first thing in the line, I think, with the Mistubishi chip the last thng.
 

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Discussion Starter · #12 ·
If I were in a position that I needed this power supply repaired right now, I'd probably just replace all those items you listed and hope for the best. Unfortunately I dont know how to test the mitsubishi chip and the transistor. For now, I'll just hold on to it as a parts power supply.


Thanks for the advice,

Chris
 

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THe way the guy who repaired mine tested them was to use his oscilloscope to check the waveform each component in the good ps made, with the waveform the components in the bad ps made. If they weren't exactly the same, we replaced the component.
 
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