Get your Prozac.
Set 1, jungle IC (???)9330 is not putting out horizontal drive. Got the disk from RCA, defective but I can view the DWG files. Also have the specsheet for the jungle. There seems to be no reason for it not to have H drive output. Additionally on a previous repair, the connector to the CRT boards touched the standby reg heatsink while not in isolation, blew out the red channel. Red channel was repaired, it was a buffer transistor and a resistor. (lucky) The set ran otherwise or I would never have fixed the red channel. Now has no H drive. Suspect IC as there seems to be nothing else to cause loss of drive.
Set 2 , Blows the convergence PS almost immediately, perhaps 7 seconds. The rest of it runs, with the distorted raster of course. Convergence out board has been swapped out, still the same.
Set 3 works.
In both sets 1 and 2 I figure work is needed on the signal board. Well the boss wanted to take a different approach and I looked into possibly doing some board jockeying. Had a junior tech do the work while I did other things.
Now this is the fun part, all the signal boards work in the one set. Set 1's sig board in the working set has H drive and works but produces a too bright picture with retrace lines. Set 2's sig board works fine with the geometry and convergence off, but not dead. Simply as if the parameters are not set to this unit, to be expected. There is no blowing of the convergence PS. H centering is off however, which I did not expect. That being off to the right, the convergence error is just about what I expect. I think if I adjusted the centering rings (if any) the convergence would be alot closer.
I told the kid to sit tight for a bit and see if any of the convergence out heatsinks were getting hot. They are not. The ones on the left (facing the rear of the set) are just a bit warmer than the rest, but not hot. Not by any means. I figure those are the blue channels, which in most RPTVs are pushed a bit harder because of the laws of physics.
I normally do not like doing board swapping, but already have the parts to fix the conv. PS so he wanted it, he got it. But now I don't get it. In set one I was going to replace the jungle IC and in set two I was headed for the output OPAMPS for the convergence. I didn't think they were shorted, their source is fused, I figured they were driving one or more channels with high DC.
I think these to be pretty logical deductions, but both have been proven wrong. I have indeed stumbled into post hoc ergo propter hoc here. The proof is on the screen.
Set 1 is near identical to set three, but set 2 has the ATSC tuner board atop the sig board. With that SB in set 3 there is no plug on the power board for it's power, so it doesn't work, but the rest of it does, seemingly fine.
Now I have heard about the 220V scan rectifier causing no Hdrive, but that has been checked in set 1. What's more the power board has been swapped out from a working set into set 1, before set 3 ever arrived.
I know this is getting confusing, but may be revealing. To summarize and clear the confusion :
Set 1 has no Hdrive out of the jungle (IIRC IX400 ?). Using the scematic and the spec sheet for the chip I can find no reason for this except a bad chip. What's more it may have been stressed by the short I mentioned. I didn't notice the plug off of the CRT socket board and tried to fire up the set, unfortunately no isolation at the time and it was grounded through the antenna. Must be more careful with these pieces of SHIT, otherwise it gets on you. Now I did fix the red channel and know it worked. What I figured had happened was that the short that blew the red buffer out may have tranferred enough of a jolt to the jungle to damage it slightly, causing a failure later. It was the only thing that made sense, but now has been proven wrong. The spec sheet also says that the Hdrive can be turned off by the bus. I was next going to figure out if there is a way to tell if this is the case.
Set 2 blows the conv PS, even though it is current limited. Both the conv out and conv PS have been swapped out. The problem is not there. With the fuse replaced and the conv PS unplugged, this one runs fine except for no convergence. It's sig board operates in set 3 , but with no power to the ATSC tuner. I know things are getting ridiculous, like a bad speaker causing no HV, but this is even more far fetched. Should I put the sig board back in set 2 with the ATSC tuner power unplugged ? Come on now, even for RCA this is wild.
I hate this cowboy style troubleshooting, but in this case I think it paid off. At least now I know to stop and regroup. I hate wasting parts, and we are not shelling out almost $300 for boards. I don't blame you if you don't want to field these questions. I would appreciate something. I think I need someone who knows some details about version changes. Set 3 seems to me like it's older, but I only derive that from the fact that it lacks the power plug for the ATSC tuner. This might not be correct though, they put things in, but they also take things out. Some other circuitry could be omitted or redundant.
Other problem is our disk for these POSs. (screw grammar) It does not run properly, all I can get is the DWG files and the PDFs. I can view the waveforms in an image editor but the links do not work. They are in PNG format but as is, they are just a bunch of files. I also have no parts list. This disk was supposedly purchased from RCA at the premium price. It is printed like a stamped CD and looks like it is stamped, there is no evidence that it is a copy, except for one thing. There is a file on the disk named pspbrowse.jbf. I happen to know for a fact that the JBF file belongs to Paint Shop Pro and JBF mean Jasc Browser File. Jasc is the company, and the file is pretty much a bunch of thumbnails. I'll have to ask exactly where this disk came from.
At least one good thing came out of it, I had been dodging this Daewoo RPTV and after these friggin RCAs I was like "Bring it on". Screw it. After an MI-35 and a TDA6111 she will be on the road :-). A friggin Daewoo ! I'm not saying buy a Daewoo, but if it were that or one of these RCAs well, sorry. don't buy the RCA. I also noticed that the Daewoo seems to use the same flyback (HVG) as an NAP PTV900 series, which IIRC are not really expensive.
That is looking like the start of a rant, so I will stop and put it in another thread.
Anyway, I do have to deal with these things. They are not going to beat me, this is not an initialization or scan converter problem. This has to do with power. Or more aptly, normal stuff. We are not inside a metal box which is simply shown as a block on the schem. This has got to be solvable.
On set 2 I have considered the possibility of a shorted conv yoke. The only way this works is if a H winding is shorted to the V winding. As you know, conv outs are a current source, so even a dead short will not cause an overload to the PS. It will overheat the outputs, but the set should run awhile. Another thing bothers me, I see source resistor on the FET chopper of the conv PS. It is supposed to be current limited. Then why does it blow ? I KNOW the problem wasn't right on the conv PS because I swapped it out from a working set. Poof !
But not in another set with any combination of boards. And this doesn't even start to address the other set. Engineers current limit PSes so that they don't fry when they get shorted out, there is no other reason. If not, that's what they make fuses for. Or is it possible that the PS is severely underbuilt and can only stand an overload condition for 7 seconds ? Can't really discount that possibility either.
The kid will not be working on this on Wednesday, I'm off, but Thursday he is going to do an ohmmeter check on all the convergence yokes in set
- I don't know exactly where to go in set 1, but Hdrive is handled by the jungle ( a 9330), as is blanking. This has got to be a clue.
Screw thanks in advance, thanks for just reading to this point. If you think your head is spinning, well I had to get those hyperfluid bearing from the future, a way easier task than fixing an RCA. :-)
JURB