New to this: CRT repair (Phlips 107S)

[goodpsusearch]

I have some CRT monitors and TVs that need repairing. Having no previous experience with CRTs, I hope I could learn some basic things from you!

The first patient is a Philips 107s 17 inch display. This was my first computer screen, bought in 1999, stopped working in July 2004: One morning I powered my computer as usual and suddenly the monitor started making noises like small explosions and the display was flickering until I powered it off.

I don't care that much about that monitor, it's just a learning project to me.

I have heard many scary stories about the high voltages a CRT can keep, but this monitor was stored for nearly 7 years so I assumed it is safe and disassembled it.

I tested every diode, transistor and capacitor that I could and they were all found ok except 2 resistors near the fly-back transformer that look burned.

I attach some photos. Do you think those burned resistors were the result of another part failure or I can replace them and make it work again?

[Th3_uN1Qu3]

Re: New to this: CRT repair (Phlips 107S)

One morning I powered my computer as usual and suddenly the monitor started making noises like small explosions and the display was flickering until I powered it off.

That was the flyback arcing. Probably to the resistors you found burned. Not worth fixing.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

That was the flyback arcing. Probably to the resistors you found burned. Not worth fixing.

Thanks!

Please can you explain to me how it arced and why? I want to learn

[Th3_uN1Qu3]

Re: New to this: CRT repair (Phlips 107S)

How: It isn't too hard to find a path to ground when you're 30 kilovolts high.

Why: Manufacturing tolerances. A flyback transformer is a part that has a very high voltage winding, wound with very thin wire. That in itself is asking for trouble - but there's also half the power supply of the monitor derived from extra windings on that same transformer! They're potted in epoxy for a reason. If there are any air bubbles left, over time, the high voltage will find a way thru to the other windings and short out.

I missed something though. All the diodes and transistors (including horizontal output transistor if i understand right), checked out okay. You haven't powered up the monitor after that incident, right? If that's so, power it on now, with the cover off, and with a mirror behind it. If the flyback is arcing, you'll be able to see it as well as hear it.

There is only one other thing that could sound like "little explosions" - an overvoltage on one of the other HV lines causing the spark gaps to fire. Most likely on focus. If the anode voltage were too high (you know, the fat red wire with the suction cup), then the x-ray protection would simply shut down the monitor. If just the focus section is bad then it could act as described.

The good news is, a bad focus section can be fixed.

I used to have one of those monitors too. Mine was a 107E4. Long story short, it sucked. One of those is worth fixing just for know-how.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

Finally my exams are over!

I took out the 2 burnt resistors. Even though they look completely burnt, their measured resistance is 22kohm. Are these their nominal values or not? Cause I can't make out the color code... I attach 2 photos in case someone is able to make it out...

[Th3_uN1Qu3]

Re: New to this: CRT repair (Phlips 107S)

Don't you have a schematic for it?

[Krankshaft]

Re: New to this: CRT repair (Phlips 107S)

If those resistors are in circuit with the flyback or the Horizontal Output Transistor that drives it the flyback's shorted.

Hair thin high voltage windings with even thinner insulation. Couple that with tons of vibration and heat which eventually causes it to fail as described.

Flybacks are vacuum potted in epoxy in order to provide extra insulation and extend their life as well.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

Don't you have a schematic for it?

I found these...

I don't know if they are the right model.

If those resistors are in circuit with the flyback or the Horizontal Output Transistor that drives it the flyback's shorted.

Hair thin high voltage windings with even thinner insulation. Couple that with tons of vibration and heat which eventually causes it to fail as described.

Flybacks are vacuum potted in epoxy in order to provide extra insulation and extend their life as well.

I suppose that means they are indeed in circuit with the flyback...

[momaka]

Re: New to this: CRT repair (Phlips 107S)

I found these...
I don't know if they are the right model.

Yeah, I don't think either of the schematics you posted are the right ones.

On your monitor's board, the two resistors are 873 and 874 (note I didn't include the "3" prefix in the name because that's just a component type indicator; in the case of your monitor, anything with a "3" prefix is a resistor, "2" a capacitor, and "5" inductor - see the pattern?). The schematic in the PDF file does no list those resistors and the PCB layout in the Word file you posted does not seem to match the one in your monitor either. Moreover, the flyback in the schematic in the PDF file does not any single pins that are connected to just two resistors like that.
I also wasn't sure if those resistors were actually 673 and 674 instead of 873 and 874, so I looked for those on the schematic as well, but couldn't find anything again.

With that said, I don't know if their value is supposed to be 22 kOhms. Are they both showing 22 kOhms? Seems that their color codes are the same - if that's the case, they may not be bad yet. But I can't say for sure. The fact that they also use 5 bands rather than 4 makes them more confusing to decode (to me, at least).

From what I can tell, the lower one is brown, brown, black, brown, brown, and the other one brown, black, black, black, brown.
According to an online calculator, that would be 1.1 kOhm 1% for the first, and 100 Ohms 1% for the second.
I would say maybe keep looking for a schematic, though.

Nice pictures, by the way.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

Yeah, I don't think either of the schematics you posted are the right ones.

On your monitor's board, the two resistors are 873 and 874 (note I didn't include the "3" prefix in the name because that's just a component type indicator; in the case of your monitor, anything with a "3" prefix is a resistor, "2" a capacitor, and "5" inductor - see the pattern?). The schematic in the PDF file does no list those resistors and the PCB layout in the Word file you posted does not seem to match the one in your monitor either. Moreover, the flyback in the schematic in the PDF file does not any single pins that are connected to just two resistors like that.
I also wasn't sure if those resistors were actually 673 and 674 instead of 873 and 874, so I looked for those on the schematic as well, but couldn't find anything again.

Those schematics belong to a different model unfortunately. A really bad thing with Philips monitors is that there are some different versions named the same (107s in that situation).

With that said, I don't know if their value is supposed to be 22 kOhms. Are they both showing 22 kOhms?

Yes, they do. They also look burnt enough..

Seems that their color codes are the same - if that's the case, they may not be bad yet. But I can't say for sure. The fact that they also use 5 bands rather than 4 makes them more confusing to decode (to me, at least).

From what I can tell, the lower one is brown, brown, black, brown, brown, and the other one brown, black, black, black, brown.
According to an online calculator, that would be 1.1 kOhm 1% for the first, and 100 Ohms 1% for the second.

I think that the lower one is: red, "burnt red", "unknown burnt", "burnt red", red

and it was originally: red, red, orange, red, red (I hope so) = 2 2 x1000 ohms 2% tolerance and the last band something about temperature coefficient

or maybe: red, red, black, red, red = 2 2 0 x100 ohms 2% tolerance

and the other resistor is: red, "unknown burnt", "unknown burnt", "unknown burnt", red.

According to an online calculator, that would be 1.1 kOhm 1% for the first, and 100 Ohms 1% for the second.
I would say maybe keep looking for a schematic, though.

Nice pictures, by the way.

I bought new 22kohm resistors and I think I am going to risk powering it with those installed...

UPDATE:

They both show exactly 22.3Kohm.

Maybe it was originally: red, red, orange, red, red = 2 2 3 x100 ohms 2% tolerance.

That online calculator agrees:
http://samengstrom.com/15924820/en/r...or_Color_Codes

[Th3_uN1Qu3]

Re: New to this: CRT repair (Phlips 107S)

I bought new 22kohm resistors and I think I am going to risk powering it with those installed...

Do it. And use a mirror like i said.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

I did!

And it clicks constantly... After some time clicking you can smell something burning.. By the time it does that I disconnect it from AC. Then I reconnect it and it clicks again and again.. and then again the burning smell.. etc.

I will try to upload a video.

[Th3_uN1Qu3]

Re: New to this: CRT repair (Phlips 107S)

Clicking means power supply in protection mode. You have a short somewhere. Could be the HOT (horizontal output transistor). If you have a bad flyback it's likely to take out the HOT.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

2 short videos

http://www.youtube.com/watch?v=qNS6rtmkOso
http://www.youtube.com/watch?v=HrdULzfCyzM

[momaka]

Re: New to this: CRT repair (Phlips 107S)

I don't know if this will be of any help, but based on the videos you posted (the first one particularly), it seems that the real model of this monitor is CM2600 (based on one of the stickers on the heatsink near flyback).
I tried looking for the service manual a bit, but most websites want a fee to download it. eserviceinfo and electrotanya didn't seem to have it.
Perhaps you may find something?

I also found a post by someone who had the same problem:
http://www.network54.com/Forum/87612...600)+resistors
no answer, unfortunately.

[kc8adu]

Re: New to this: CRT repair (Phlips 107S)

iirc those resistors are on the abl pin on the fly.99.999% of the time if they burn the fly is bad.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

I don't know if this will be of any help, but based on the videos you posted (the first one particularly), it seems that the real model of this monitor is CM2600 (based on one of the stickers on the heatsink near flyback).
I tried looking for the service manual a bit, but most websites want a fee to download it. eserviceinfo and electrotanya didn't seem to have it.
Perhaps you may find something?

I also found a post by someone who had the same problem:
http://www.network54.com/Forum/87612...600)+resistors
no answer, unfortunately.

Look what I found:
http://www.electronicspoint.com/moni...00-t59073.html
http://www.edaboard.com/thread71951.html
http://www.scribd.com/doc/53049599/Service-Philips-2005
but still nothing useful I think.

iirc those resistors are on the abl pin on the fly.99.999% of the time if they burn the fly is bad.

Oh, well. Maybe it's time I let this CRT rest in peace and move to the next patient.

[momaka]

Re: New to this: CRT repair (Phlips 107S)

Look what I found:
http://www.electronicspoint.com/moni...00-t59073.html
http://www.edaboard.com/thread71951.html
http://www.scribd.com/doc/53049599/Service-Philips-2005
but still nothing useful I think.

That last link may be, but I don't have a Facebook account anymore so I can't verify.

Oh, well. Maybe it's time I let this CRT rest in peace and move to the next patient.

Sounds good. Before disposing of it, see what problems the other monitors have, though. Maybe you might need to reuse some parts from this one.

[goodpsusearch]

Re: New to this: CRT repair (Phlips 107S)

Some freebies!

Philips 107P5
A flat screen, high resolution and refresh rate 17" CRT monitor!

It's really nice looking and has an excellent display quality.

I took 3 of them for free and there are 2 more left. I wish I had space...

The reason they throw away those monitors is that the power button breaks and gets stuck, preventing the monitor from powering on! A really easy fix!

[momaka]

Re: New to this: CRT repair (Phlips 107S)

Some freebies!

Philips 107P5
A flat screen, high resolution and refresh rate 17" CRT monitor!

It's really nice looking and has an excellent display quality.

Niiiiice!

So, is the tube shadow mask or aperture grille? Maximum (readable) resolution? What about refresh rates, how far can you push it?

I didn't know CHUNGHWA made CRT tubes, though. Where is it made? I do have a 19" Wise Wing LCD monitor with a CHUNGHWA TFT. Looks almost as good as my family's Dell (BenQ). I guess CHUNGHWA makes decent stuff.

I took 3 of them for free and there are 2 more left. I wish I had space...

Yeah, I have that problem too. Today I saw a flat screen Samsung CRT thrown out by one of the dumpsters I check every Friday. It looked pretty good and clean, but I really have no space (well I do, but my family will kill me ). Not sure if it was 17" or 19". I might go check it out again tomorrow, just out of curiosity (hopefully it will still be there). If it's a SyncMaster 997DF, I'll be very tempted to take it. Right now, I have a SyncMaster 955DF - it looks good, but image quality is only okay (too bright and thus colors are a bit washed out). The 997DF is the more expensive version of the 955DF, and has a much higher resolution and better features.

That aside, you should have taken 4 of them and done a quad-monitor setup .