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Full Version: What Can Litherish Do With His 50" Rptv?
Lumenlab > Audio Video Sciences > Advanced Projector Builder > RPTV
Litherish
Well, I found an old 1991 Hitachi RPTV listed on craigslist for 50$ and I decided to buy it.

Everything appears to be sound except for convergence, the only reason he was selling it was that he just upgraded to a big LCD flat panel.

The convergence on the TV is screwed up, so first I went into the menu's convergence setting's which were minimal and didn't help me much. Then I downloaded the service manual for it and found where the convergence controls were.

Convergence control board->


At first I was terrible at convergence, my picture got worse and worse...But then I got better and slowly but surely the image started to become converged.

One problem though, something about the convergence is really screwed up, sometimes the screen will flicker and the image will become much darker, and then all the colors will be mis-aligned. But it will pop back in a bit to the original convergence.

As of now convergence is a slow process because the screen keeps "popping" back and forth between the dark screen and light screen. I'm unsure as to whether this problem will persist once the convergence is fixed and nothing touches the board.

When I put pressure on the convergence board, or parts of it, this problem seems to occur.

Does anyone have any knowledge about fixing this sort of thing? Would a heat gun maybe loosen up some solder joints? And the internals of the actual RPTV are really dusty, do you cleaning the dust out might help?

I'm thinking it might be better to just salvage any parts and put a DIY in there like SPK did. But that is a lot of work, and money.
Litherish
Well it looks like one of the transistors or something on the convergence board just completely died. The picture is now very dark, and does not get brighter, even for a second. I have spotted the broken thing I believe, the only problem is I dont really know where to find the parts, and the places Ive looked are really for big quantity orders...

I think that if I don't find an easy fix soon, the CRT tubes go up on Ebay, and I gut the monster, it is spacious inside so no need to do any modifications to the case except taking out the controller boards and what not.
DAZZZLA
QUOTE (Litherish @ Oct 17 2006, 10:30 AM) *
Well it looks like one of the transistors or something on the convergence board just completely died. The picture is now very dark, and does not get brighter, even for a second. I have spotted the broken thing I believe, the only problem is I dont really know where to find the parts, and the places Ive looked are really for big quantity orders...

I think that if I don't find an easy fix soon, the CRT tubes go up on Ebay, and I gut the monster, it is spacious inside so no need to do any modifications to the case except taking out the controller boards and what not.

Do you have a pic of the component or it's code?

DJ
Litherish
QUOTE (DAZZZLA @ Oct 17 2006, 02:21 AM) *
Do you have a pic of the component or it's code?

DJ

One part is-> 0700048 And the component is -> CF 3.9K OHM +-5% 1/16W
The other is part-> 0150136 And the component is -> VR 5K OHM-B

I got these directly from the service manual replacement parts based on the number near the broken part on the convergence board. Do you know of anywhere I might be able to order these in just one quantity? Google didn't turn up much small businesses selling these.
DAZZZLA
The first component is a carbon film resistor, 3.9k ohms, 5% tolerance ¼ Watt will do, I don’t think I’ve seen one that is 1/16th of a watt unless it’s a surface mount type.
The second component is a variable resistor or potentiometer, 5k ohms, linear.
Both of these components are very common. Try an online electronics shop in the US or give me a link to one and I’ll look them up for you. A pic would help to confirm their mechanical sizes.

DJ

Edit:
What makes you think the components are burnt out?
Litherish
Thanks for the responses DAZZLA smile.gif , I've taken some pictures including both broken parts.

Here is the mammoth... ->

Convergence Board ->

Here is one of the broken parts (at least I think it's broken) ->

Close-up of the other broken part, it is an adjustable convergence thing ->

Different part of the convergence board ->

I actually don't know if either of these parts are the cause of the TV fluttering from dark to light, which it does now...How do I figure out what is broken? I have the service PDF with all the wiring diagrams, do you think that checking all the voltages on the convergence board would be the way to test what's working and what's not? That would take a while...

A quick search found me this site http://www.electrospec.com

Btw, how did you edit your post without having edited appear at the bottom of your post?
DAZZZLA
Two possible sources:
Mouser
Trimmer
Resistor


Digi-Key
Trimmer
Resistor


Just check that the mechanical sizes are simular.

DJ
Litherish
QUOTE (DAZZZLA @ Oct 18 2006, 08:21 PM) *
Two possible sources:
Mouser
Trimmer
Resistor
Digi-Key
Trimmer
Resistor
Just check that the mechanical sizes are simular.

DJ

Thanks for those sources, they are really cheap! One problem though, I don't know if these parts are the problems, the one "Trimmer" is off and the TV still turns on and switches between light and dark. I'm beginning to doubt I'll find a way too fix the convergence board without a full replacement, which becomes expensive and hard to find. sad.gif

I think it might be time to throw the CRT tubes up on Ebay and build a DIY into it? I mean I could take all the numbers from the Convergence board in the PDF and find every single replacement part for them and do it that way, but for 640x480 not so good resolution I don't think that's likely...

Input?
DAZZZLA
You mentioned that the flicker happened when you put pressure on the board. If this is the case then it sounds like either a dry solder joint, a worn trimmer or broken component. The easiest way to fix a dry joint is to re-solder all the components in the section of the board that you think it is located. A worn trimmer usually shows when you turn it. Try using a toothpick to poke and prod different parts.

DJ
paladin
I don't like the look of the white connector in the bottom left of this pic. The area near the black wire seems to be
discolored, possibly a bad connection.

http://img208.imageshack.us/img208/5932/imga0042af3.jpg
Litherish
Thanks for the input, I'll try taking a toothpick to the board! I'll also take a look at that spot you suggested Paladin, it might be trouble.

Btw, I just bought a Proxima DP9260+ ! I got the whole package for 350$ shipped.

http://www.projectorcentral.com/Proxima-DP9260+.htm
Litherish
I took a heat gun too the convergence board...didn't really do much! I also resoldered on the two connecters that were broken off. Since I don't really think they were broken anyways.

I'm going to clean out all the dust and crap inside that has accumulated inside the RPTV, and see if that does anything.
Litherish
Cleaned out the dust and crap on all of the internal boards! Once again to no effect! The picture is now doing all sorts of strange things...on the good side convergence looks to be doing better! I've been reading up on SPK's plog, looks like it shouldn't be too hard to build a DIY into it...Just a regular projector with a mirror after the triplet to deflect it into the big mirror then onto the screen.

I just don't know about all the lining up of the picture to make sure it fits in the screen and is focused...
Khun Jean
You might try some 'cooling' spray. I don't know the right word for it but it is a spraycan with a small tube, it sprays something that evaporates quickly and cools down the object you sprayed.
If you have a display that switches between good and bad you probably have a bad component. With the cold spray you have a good change of locating it, just spray on every component one by one.
It is worth at least a try.
Litherish
QUOTE (Khun Jean @ Oct 23 2006, 04:18 PM) *
You might try some 'cooling' spray. I don't know the right word for it but it is a spraycan with a small tube, it sprays something that evaporates quickly and cools down the object you sprayed.
If you have a display that switches between good and bad you probably have a bad component. With the cold spray you have a good change of locating it, just spray on every component one by one.
It is worth at least a try.

Thanks for the advice, I'll have to pick some of this stuff up. I googled it, but I'm not quite sure what I'm looking for, do you have a link to somewhere that sells it? smile.gif

Thanks!
HDTVaddict
QUOTE (Litherish @ Oct 28 2006, 01:03 PM) *
Thanks for the advice, I'll have to pick some of this stuff up. I googled it, but I'm not quite sure what I'm looking for, do you have a link to somewhere that sells it? smile.gif

Thanks!

I believe this is the stuff:
http://scientificsonline.com/product.asp?p...hcd2=1162136210
http://www.mcminone.com/product.asp?catalo...amp;ATT=froogle
http://www.all-spec.com/1/viewitem/MCCFRZA/ALLSPEC/prodinfo/

Never actually bought from any of them.
Litherish
QUOTE (HDTVaddict @ Oct 29 2006, 09:42 AM) *

Thanks HDTVAddict for the links!

Apparently you are better at googling then me!

I'll probably order some later this week.
Khun Jean
Yep, that is the stuff i mean.

Your local electronics shop should have it, it is quite common.

Try to get one with a small tube you can attach to the nozzle. That way you can cool single components easy and can keep the container vertical and out of the way of other electronics. This has to be used while you have the circuit board your testing switched on. Having some distance between the board and the spraying can is a lot easier with a tube.

Good luck.
Litherish
No I did not die! And neither did this RPTV. I'm actually spending a little bit on replacement parts for some of the IC STKs that were damaged and need to be replaced. I just bought them today, and hope to get them soon.

I want to see what it looks like regular before I actually take it apart, and attempt to do what SPK did and retro-fit a DIY into it.

~Lith
Litherish
I bought a few STK-7274 chips. And one STK-7275 chip, the STK-7275 arrived today, once I get the other 3 I'll fire up my soldering iron and see what I can do.
Allen
QUOTE (Litherish @ Dec 14 2006, 04:08 PM) *
I bought a few STK-7274 chips. And one STK-7275 chip, the STK-7275 arrived today, once I get the other 3 I'll fire up my soldering iron and see what I can do.


Any results?
Litherish
QUOTE (Allen @ Dec 30 2006, 10:07 PM) *
Any results?

I'm not the best solderer, so I'm going pretty slow, and I have desoldered 2/4 STKs. I'm going to desolder the rest then see what I can do about puting in the new ones.
Litherish
Once I got the hang of puting in the first STK, I was able to do the rest. Right now I'm waiting for some glue to dry and then I'll be able to put the board back in the RPTV and see what happens.

Who knows, I may end up going DIY after all smile.gif
Litherish
QUOTE (Litherish @ Jan 10 2007, 07:41 PM) *
Once I got the hang of puting in the first STK, I was able to do the rest. Right now I'm waiting for some glue to dry and then I'll be able to put the board back in the RPTV and see what happens.

Who knows, I may end up going DIY after all smile.gif

Argh...I got everything back together, put the board back into the TV, screwed in everything, turn on the TV. AND BANG, same problem. Didn't change a damn thing. I'm thinking of selling this for what I got it for 50$.

Looks like I'm a pretty bad TV repairman.

Anyone interested it is $50 in the trading post, Madison, WI area buyers welcome to buy it. http://www.lumenlab.com/forums/index.php?showtopic=17602

~Litherish
kakureru
does it still flicker?
Litherish
QUOTE (kakureru @ Jan 12 2007, 11:53 PM) *
does it still flicker?

Yeah, it flickers from light to dark, but right now I'm working on trying to fix it with the help of pjgibbs. smile.gif
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