CurtPalme.com Home Theater Forum

[JustGreg]

[Sparky015]

I've got an ESD setup on my bench, so I'm safe, or should I say loose components are! Many people don't think too much about ESD and what it an do to a component. If it doesn't take out a component, it can certainly weaken one. The static discharge you can feel is in the kV range. It takes less than a 100V to kill sensitive ICs. You can't feel that amount of discharge. I don't take any chances. A mat and ground strap is cheap enough.

[Sparky015]

Alright guys, I finally got back to the pj and picked up a spare HDM from Dragan. I fixed my grounding issues and tossed the HDM in the pj and behold, the nice sound of static as the tubes powered up!! Then a few seconds later, an arc on red. I then frantically hit the power button, but alas, it was too slow to power down, the HV collected itself and promply arced again, giving me an H-fail and V-fail light. Arrrrgggggggggggh!

THe v-fail is not that big a deal. It smoked a resistor on the red channel, so that one won't be hard to diagnose. I now have two failed 08P Ultra HDMs though, that so far have proven to be not so easy to diagnose.

To add to it, the arc is still present on red, so my originating problem has not been resolved. thinking out loud here, possible failure modes:
1) I checked my yokes and they measure OK with an ohm meter. I suppose a high pot test would fully vet it, but I would think a bad yoke would be seen with a simple resistance measurement, no?
2)Would an improperly seated HV wire cause these symptoms?
3)The last thing is a bad tube, although I think Terry said he tested them all before they went out the door. If it were a bad tube would it arc as it has been doing? HV comes on, tubes start to power up by the sound of static, then an arc, a pause, then a second arc.

Let me know what you guys think.

[Sparky015]

thinking some more, since my failure on the vertical board is on the red channel, the arc went through the focus coil as well. Static build up on the tube, transferring to the yokes and coils, causing the board failures. Soooo, what would cause static build up? Improper grounding (aquadag straps), improper seated HV anode lead (??not sure).

Scratch the focus coil statement, I got my wires mixed. The veritical is also on the deflection yoke.

[Nashou66]

[Sparky015]

So I yanked the tube assembly and pulled the magnetics. Again, a visual inspection yielded no issues, a resistance check of the deflection yoke yields same resistance of known good yokes. So, I concentrate back on the tube. Would a bad tube cause a static arc like this? Inspection of the HV lead boot reveals some tears, probably from when I removed it from the original tube. Not sure they go all the way through. My next step is to cut away the silicone and remove it for closer inspection. I also wanted to see that it was properly seated.

[Sparky015]

Thanks Nash, sounds like that's the difinitive way to figure it out wher the arc is originating. Unfortunately for me, these arcs are being catestrophic on my boards!

I'm now confident of my grounds. I even checked from the tube all the way back to the neck board on all my tubes and my 8" red and all come back with very similar resistance values., aproximately 130 ohms. I have a hard time believing it's a bad tube, as I would think if it was, it would be an internal arc, so that leaves the HV lead, which was known good before this whole party started, so it has to be either my install, or the damage I caused when removing it. This was the first one I removed, so this boot got a little more manhandled with the channel locks than the other two. The other two have no tears, as I used needlenose and went underneath the boot to squeeze the two conductors together for removal, which was much easier and less agressive.

[JustGreg]

What a drag Paul...but I can commiserate. I installed the 'new' B&G tubes last night and......

NOTHING. Set powers up, HDM relays click with the call for HV relay latching 5 or 6 seconds after the others and no joy. No error lights...it 'should' run. No (undesired) snaps or pops, but most importantly...no (desired) crackle.

I checked most of the usual suspects but now I have to remove the red tube and check the black wires at the header connection. After putting in the red a couple weeks ago I noticed I had to reseat the HDM a couple times before HV kicked in. Could just be a coincidunce and the problem lies elsewhere.
After that I'm going to try another CLM and PS's. After that...I got nothing else I can think of to try. I already ruled out the NB's and improper connections. Even changed out the splitter block and pressed the red reset button. (Hey...it was late and I was deperate)
*sigh* The only thing I found was the white wire for the blue tube stig had been pulled out of the connector and unfortunately I powered it up with it like that before I found it whilst troubleshooting later. I don't think that would cause any harm tho as it didn't short anywhere and stig isn't 'needed' to make the set run.

Sorry for the segue but I figured this would get read by you since you're hands are already full. We'll get them working eventually. We (CRT-ers) never say never!!!!

Good luck man....you'll get it! IIRC Nash was working on figuring out how to fix HDM's so maybe they can be fixed by us non EE types. I could be wrong....I was once...but I discovered my mistake and divorced her.

[Sparky015]

Sorry to hear, Greg. I hope nothing happened to those tubes in transit. The wire pulled out of the connector is a bit disconcerting. No error lights make for even a tougher diagnosis. Just so you know, I hear the relays as well, so that doesn't mean much. Something is is not allowing the HV to kick on, it's just not giving you an error light. I'd send you an HDM to try if I had a working one! Sounds like an HDM not seating issue to me. If I read the theory of operation correctly on the HDM, it produces H-fail signal, which is processed by the DPB board on the CLM, which lights the H-fail diagnostic light. If you are having HDM seating issues, that will cause the HV not to activate, but won't produce a diagnostic light, as the HDM is not plugged in to do so. Others here more familiar with the pj than me can confirm or toss the BS flag on that, but if you had HDM seating issues to start, and you didn't rectify it, I would start there. I believe your machine is on the ceiling as well, no? I know the HDM and focus have a tendancy to unseat themselves, so many owners place a piece of foam between the board and cover to keep it seated in place.

I'm reasonably confident my issue is a bad HV boot due to my shotty install. I also think it's not seated correctly, so the entire voltage is arcing to the deflection coil, which is why it only takes two arcs to drop the horse, whereas nash's instance is able to take multiple arcs without board failure. THat's my theory, anyway. I'm getting ready to cut away the potting and have a looksy before I call it a night. I'm confident I'll figure out the HDMs, my main concern is the tube. I'll be sick if it's a bad tube. I can deal with a bad boot, just goober it with silicone. Just sucks because it's a newer style HV lead.

[Sparky015]

OK! Making progress on the arc front. I removed the HV lead and found two things. First, it was seated, BUT I used too much silicone, and I must have moved it around when trying to get it seated, as silicone rode up to the anode part, and a tiny bit was on the metal lead itself. I need to check the tube end to make sure it's free and clear of silicone. There was none at the prong, so I think I had a connection to the tube, but I'll investigate nonetheless.

The second thing I found was a hole in the boot where I saw the damage from the channel locks. Under light, I can see the metal lead through the boot, so I'm confident I found the source of the arc (thank god, because my electronics are taking a beating).

So, I need to clean up the caulking, re-install the HV lead, and booger the boot up to repair the hole. Then next up, fixing my vertical and HDM boards. Yeah buddy.

By the way, a question to you PJ experts. Is boogering up the boot with silicone a valid fix, or should I get my search on for a new HV lead (which seem to be coming up rare these days since VDC no longer sells them). Let me know your thoughts. I'm calling it a night, so I'll start in on my repairs and troubleshooting tomorrow after work.

[JustGreg]

Thanks for the info Paul; about your progress and my particular problem. I learn alot when other people post in a detailed manner like you do.
Yeah I wouldn't try to reuse the lead or boot again if given the choice but you've seen alot of the boots on tubes....the silicone is absoultely GOBBED on. I used to think it was just to reinforce the boot but who knows. It might be a good thing to do to even a new one with no known holes.

I don't think my HDM is bad either. And there is something to the HDM needing to be reseated serveral times after putting in a new red tube a couple weeks ago. I already reflowed the pins on the connector a couple weeks ago but I should look at it all again just to rule that out. It ain't rocket science after all. (good soldering).

I'm more concerned a solder joint is broken at the female HDM connector mounted to the motherboard. It's possible with all the slamming and wiggling of the HDM this pj must have gotten over the years prior to it getting to me. If the rear heatsink isn't open that end of the cages are supported by a screw through the heatsink. When it's open is the problem. I added a wire support to each one with a male/female insulated staycon connector in the middle. It still doesn't hold all that great. I'll have to squeeze the female together a bit.
As far as the covers to the cages go, I used a non ferrous screw from an old parts Marquee and drilled through the dimple of the cover to secure it throug the existing hole the dimple is "supposed" to hold it with. I got tired of the not knowing factor.

And yes...the pj is ceiling mounted so pulling it all apart to drop that mobo is gonna SUCK! It already sucks to try different PS's as I have to lower the thing down. I have an electric winch but it's still a wiggle and jiggle dance trying to keep it from gouging the boxed in I beam 4 inches in front of it.

*sigh* I 'just' want to watch a freeking movie for Pete's sake! lol

[Nashou66]

Hi Paul, I used rubber tape, the kind that you can pull and stretch out. I pulled it all around my boot and made sure it was really tight. then I put some silicon on my finger and just spread it over the tap where i knew the spark came from(hole). its held up so far. but its my test Thomas tube I am using for my Barkenstine coil testing so it doesnt get as much use as yours is.

On your HDM check the transistor that MP mentioned. i bet its that. its on the daughter board. also look at any resistors that are in the H coil circuit as well as the resitors right on the Deflection coils. With those you might have to remove the resistor to check.

Athanasios

[macgyver655]

A few RPTV service bulletins call for a nice thick layer of silicone over the entire external boot regardless of new or used, holes or not. I would just cover it with silicone and not worry about it.

[JustGreg]

[Sparky015]

THanks guys for the replies. I'll have to investigate the rubber tape. That sounds like an excellent idea coupled with the silicone.

Yes, I can attest to many frustrating times in the lab when I breadboard up a circuit only to find it doesn't work. Search and search, even rebuilding the circuit from scratch just in case I miswired, only to find that I have a transistor that looks ok, even checks out ok with a diode check, but is a dud. Only testing it in a basic circuit (or transistor checker) vets it out fully. I think I may do that here when I get to repairing both HDMs. I think I'm going to bread board up a basic circuit since the majority of the transistors are the same type and check them out. I was planning on using the new spare as a benchmark when diagnosing my original, but not any more!

It's alright, I'm just happy it was an HV boot and not a bad tube. Just sucks that my lack of experience replacing tubes is what caused this mess, but that's how you learn, right?

[Sparky015]

Question to you CRT techies. I've made repairs to my tube, and I believe I've repaired my spare HDM. I now just need to fix the vertical module. The resistor that blew is R720, which is a 1 ohm fusible on the 15V line for the vertical deflection booster IC (STV9379). So to the question, do you think the resistor blew because the arc took out the IC, or did it blow because the arc made the ground hot and blew to save the IC? I should have the resistor replaced tonight (the weather has been great this past week, so I haven't spent too much time inside to work on the pj) so I will know either way soon enough. I checked mouser, and it looks like that STV9379 IC is obsolete, probably because it was only used for CRT. Let me know what you guys think.

[Nashou66]

Id remove the IC and check it. But their should be a close replacement. I think I have a link somewhere on my Home Comp for it, maybe. When I first got into doing all the repairs I went nuts and looked up every part on mouser,newark,and digikey and looked for similar replacements.That might be one of the 3-5 i did not find.

Athanasios

[Sparky015]

I didn't do an in depth search yet, but my initial search came up empty for a subsitute. This looks like a CRT dedicated IC. I may pull it and bread board a basic circuit to check it. Looking at the datasheet, there doesn't seem to be an easy way to check it on the bench. I don't have enough spare components, so I may have to order some to make the basic circuit. I have a function generator and a DC supply, so it should be easy enough to check.

[macgyver655]

The only thing you can test out of circuit on that chip is for pin to pin short or short to gnd. Functionality can only be tested via scope while running.

Chip is still available and also crosses to TDA8179.

[macgyver655]

Oh, it also crosses to NTE7170