CurtPalme.com Home Theater Forum

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

My boss has two minty PG9000s one is in the closet and one on his ceiling, the closet model has sat there for years in it's box, waiting for some action, now he got it...
The unit is almost never used, however it has some spot-burn like thing on the red tube face, but not in the middle of the tube, long story short: I replaced a bounch of leaking caps on various boards, before thinking of turning it on, now as I finished my work thought it's time to power up the machine (I didn't touch the HVPS board before).
So everything seemed just right except for two power resistors on the HVPS board blew up (R5566, R5576) right after the HV came alive. Actually I have a full set of NEC plain PG HVPS, but I am hesitant to throw that in, 'cause I don't want to blow that up too, so any ideas what to look for: LVPS, tubes, ... ? I've never heard of such a problem in a NEC.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

You may want to check the 110v supply with the HV board removed.

Did you do anything in the LVPS?

What's the board number on that HV board?

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

No, I didn't touch the LVPS, however I planned...
It's a PWC3714A, 72137142 board with 1E7-243AJ inkstamp number, this is exactly the same to what I have here as a spare board.
I'll look at the 110V line tomorrow.

**Curt Palme** · Posted: Mon Dec 10, 2012 11:06 pm Post subject:

I have a zillion of those. Throw the spare in, I'll bet it will work, however it may shut down, as the boards are calibrated to the sets, like all NECs. You'd need an HV probe and the knowledge not to blow yourself up to calibrate the board. Try it though, and see what happens.

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

Ok here is the plan: I'll check the 110V first if it is right will put in the spare board, but will unplug all tubes from splitter and then plug them back one at a time.
I do have acces to HV probe, and have the service manual with the procedure of recalibrating, so that's not a problem, however I never did such a thing yet...

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

Ok, this beast is still acting. In the meantime I recapped the LVPS, checked the 110V supply, and it is fine. I put my spare board in and that blowed up too!
-So repaired the burned resistors, and pulled the KA,KB connectors (flyback transformes), then the HVPS seemed to work (at least it didn't blow up).
-pulled out the tubes from the splitter, the HVPS still wanted to blow up.
-I replaced the whole HV stuff (Flyback assy, merger, splitter) to my known working ones, the HVPS still wanted to blow up.

At the end I think I did a mistake, because I thought it will be a good idea to connect only one FBT to the board, then the whole FBT assy arced to the ground.... after that the R5517 also blew up, I guess that nuked the UPC494 this time.

But the question still remains, why is the HVPS still blowing up, albeit replaced all parts (and the parts came from the same set, so the parts were trimmed

**Curt Palme** · Posted: Fri Sep 13, 2013 5:23 pm Post subject:

the NEC HV sections are very reliable. I've only had one set in 13 years that popped the HV section, and that was intermittent, about every 20 hours. I suspect a shorted HV transformer or HV splitter. In fact, the last thing I heard from Doug baisey, the NEC expert, was that NEC said to replace the HV board, splitter and transformer all at the same time, then calibrate the Hv board to the new parts installed.

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

stefuel · Posted: Fri Sep 13, 2013 10:42 pm Post subject:

I really feel the need to ask this. Why did you start replacing parts BEFORE you even tried to run the projector?
The HV board did not blow until you tried it after the fact. At least you would know if it was something you did or not. I don't do anything without trying it first.

1. Confirm that it is broken.
2. Locate and repair the problem
3. Get the device running reliably
4. Then play cap boy.

**Curt Palme** · Posted: Sat Sep 14, 2013 12:34 am Post subject:

Chip, this is a no win situation. Frankly, if I was determined to get an old NEC running, where everyone said that capacitors go bad often on these sets, I'd probably recap any suspicious looking/measuring caps as well before firing it up. It's sort of like replacing a bunch of hoses and maybe the oil pump in an old engine.

As I've said a few times here now, I will sell boards dirt cheap for NECs at this point due to massive problems with these PG sets. Best case I'll test them in a set before shipping, but I've now stopped servicing them due to all these issues.

I have no idea why two HV boards died in the PG, and violently so. Because I really can't add anything to this troubleshooting process, I'll bail out on this one, sorry!

zxh398 · Joined: 05 Nov 2009 Posts: 55 Location: china guangzhou

I think you put the machine replaced, the effect is really too bad 9000

zxh398 · Joined: 05 Nov 2009 Posts: 55 Location: china guangzhou

9000 Too many capacitors need to be replaced. Various boards vulnerable,

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

Ok, just rechecked the 110V supply line, and now it's not ok... Without the HVPS board connected to the PK connector I measure as high as 160V right after switching on, then goes down to 140V. In the LVPS I've found the adjustment of the 110V line, but that only allows me to set between 138-142V.

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

What is it like in the other set?

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

130V right from start up, without HV board attached. But that set is somewhat older I think, that has slightly different HV board too, it doesn't have the long life/high bight switch on it.

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Seems quite high...

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

I put the other LVPS in it, without the flyback block attached to the HV board the 110V line settled at 113V (note: without the HV board it was 130V). Then I connected the rest of the HV parts (except the tubes) and voila the set fired up without blowing up the HVPS, so the LVPS which is sick.