204B freezes after caps replace

[ztrekr]

I've replaced all 820, 330 and 47 uF caps in my Samsung SyncMaster 204B and now the back-light turns on.

But as soon as it turns on, the monitor "freezes", i.e. doesn't respond to the power button on the front panel and no image is displayed - just blackness.

Before the light goes on the power button is operational, but I can't see the menu or anything. But as soon as the back-light activates, the button stops working (the blue light on the button still on).

Also the humming noise inside the monitor stops as soon as the light goes on.

What could be the problem?

[vinceroger69]

Re: 204B freezes after caps replace

i would remove clean and reseat all the cables could just be a bad connection. re check your soldering on the capacitors just incase you have bridged 2 tracks together by accident

[selldoor]

Re: 204B freezes after caps replace

Hi - please can you update your country and mains voltage in your profile.What problems did your monitor have before your replaced the caps.
What make/series of caps did you use for replacements.
Please check your soldering for cold joints and make sure caps are the correct
way round.(Polarity)
Try disconnecting the lvds cable - video board to panel and see if the back lights stay on.
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

It will be useful if you can say a bit about yourself - skills tools etc.

[ztrekr]

Re: 204B freezes after caps replace

Of course I've checked all the trivial things before posting
Polarity, soldering, wires...

I even went so far as to replace the capacitors yet again with a new bunch of fresh ones, in case there was a factory defect in one of them or bad soldering.

Anyway, the back-light now works perfectly, so I guess the power supply unit is now Ok and the problem is probably in that other board that is responsible for actual displaying. I think some internal microcode or settings got corrupted.

I've seen posts here where people reported bad colors or corrupted image after capacitors replace and it was solved by reseting to factory defaults. Unfortunately, I can't reset to factory default because I can't see the menu.

And holding the front panel's "Enter" button doesn't work either because the back-light goes on in about 2 seconds (then monitor freezes) and you need to hold the button for 5.

So is there a hardware way to reset to factory defaults, like shortening some pin on the board or something?

[selldoor]

Re: 204B freezes after caps replace

Please can you update your country and mains voltage in your profile.
What problems did your monitor have before you replaced the caps.
What make/series of caps did you use for replacements.

We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attachm...1&d=1290283049

https://www.badcaps.net/forum/attachm...7&d=1280167246

It will be useful if you can say a bit about yourself - skills tools etc.

[ztrekr]

Re: 204B freezes after caps replace

Today I've found out that my replacement caps are probably not low ESR

They are Jamicon TK series:

http://www.icd-sales.com/Manufacture...ies-table.aspx

How critical is low ESR? Is it possible that this can cause freezing of the microcontroller board in my case? As I said, the back-light seems to be working fine...

[selldoor]

Re: 204B freezes after caps replace

Well, one out of three requests answered - this is going to be a long thread.
Short term,low esr caps will work but will be short lived and may take out other components as they fail - they are also only 85deg caps so will react badly with heat.


Please can you update your country and mains voltage in your profile.
What problems did your monitor have before you replaced the caps.


We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attachm...1&d=1290283049

https://www.badcaps.net/forum/attachm...7&d=1280167246

It will be useful if you can say a bit about yourself - skills tools etc.

[ztrekr]

Re: 204B freezes after caps replace

Please can you update your country and mains voltage in your profile.
What problems did your monitor have before you replaced the caps.

What my country and mains voltage have to do with anything?

The problem was standard "2 seconds to blackness" problem.

[mariushm]

Re: 204B freezes after caps replace

What my country and mains voltage have to do with anything?

The problem was standard "2 seconds to blackness" problem.

If we have to recommend some components for you to buy to fix your monitor, it helps to know where you're from, so we can give you links for the more convenient store.

Ex. If you're in Malaysia, I could give you links to Digikey and be charged 40$ for shipping from US to you, or I could give you links to element14/newark which has warehouse in Singapore and have free shipping or you pay only a few dollars to ship.

Post pictures of the boards if you can, sometimes experienced people can spot areas with problems that you may not think about or spot by yourself or can suggest to do some measurements on some components in case something else is the problem in your case.

[selldoor]

Re: 204B freezes after caps replace

Well country was one of the compulsary fields when you applied to be a forum member.

The Mains voltage in my opinion is actually more important as it tells us what to expect
as a result of certain tests. It is also important from a safety point of view 240 volts is more likely to kill you than 120 volts.

Less important. If you dont supply the information I will not try to assist you, which I guess will not bother you in the least.

[ztrekr]

Re: 204B freezes after caps replace

It is also important from a safety point of view 240 volts is more likely to kill you than 120 volts.

Yeah, like you're gonna be liable if I die poking inside my monitor... Let me worry about my own safety.

Less important. If you dont supply the information I will not try to assist you, which I guess will not bother you in the least.

What are you, some kind of racist? What's with this laughable blackmail?

[mariushm]

Re: 204B freezes after caps replace

He's not employed here to help everyone, and you're not paying him anything.

It's not blackmail, it's just his personal decision to not help anyone that doesn't follow instructions designed to keep things running smoothly.

[ztrekr]

Re: 204B freezes after caps replace

He's not employed here to help everyone, and you're not paying him anything.

It's not blackmail, it's just his personal decision to not help anyone that doesn't follow instructions designed to keep things running smoothly.

"If you don't provide info I won't help" IS blackmail.

Childish, unreasonable blackmail, because my country and mains voltage have nothing to do with the problem at hand.

[t.j.]

Re: 204B freezes after caps replace

no blackmail! your just ignorant! what was asked was to make helping you easier ! you seem to know everything, good luck!

[tom66]

Re: 204B freezes after caps replace

Trust me 115V hurts just as much as 230V and both will quite easily kill you in the wrong circumstances. But it's quite difficult to do if you're careful.

Let's guess that you are using 115V AC because as far as I know the Syncmaster "B" series was a US only model.

Your Jamicon TK caps probably won't do the job and are likely to at least be part of the problem.

[ztrekr]

Re: 204B freezes after caps replace

Let's guess that you are using 115V AC because as far as I know the Syncmaster "B" series was a US only model.

Well, you guested wrong It seems that the B model is also available outside US - I have a 220 V grid.

Your Jamicon TK caps probably won't do the job and are likely to at least be part of the problem.

Ok, got it, thanks. I will try to find proper replacement caps here.

Until then - is there a way to reset EEPROM on the board somehow? I think its settings just got corrupted and that's why it freezes. I have 0.1 rev board.

[tom66]

Re: 204B freezes after caps replace

Well, you guested wrong It seems that the B model is also available outside US - I have a 220 V grid.

Another reason to specify line voltage... Since you refer to it as "220" are you in Europe (excluding UK?)

Ok, got it, thanks. I will try to find proper replacement caps here.

Until then - is there a way to reset EEPROM on the board somehow? I think its settings just got corrupted and that's why it freezes. I have 0.1 rev board.

On Samsung TVs the procedure is to short pins #5 and #6 of the 8 pin EEPROM together while the monitor is starting up. I don't think your EEPROM is corrupt though, I think it's more likely it's not booting because the power supply is not stable.

[ztrekr]

Re: 204B freezes after caps replace

Another reason to specify line voltage... Since you refer to it as "220" are you in Europe (excluding UK?)

Yes, I'm in Europe, but not in the UK.

On Samsung TVs the procedure is to short pins #5 and #6 of the 8 pin EEPROM together while the monitor is starting up. I don't think your EEPROM is corrupt though, I think it's more likely it's not booting because the power supply is not stable.

Ok, then I will try to find proper capacitors, replace them and see what's going to happen.

[ztrekr]

Re: 204B freezes after caps replace

UPDATE: I haven't replaced the caps with low ESR ones, but managed to measure the voltage from the power supply to the microcontroller board - it stays the same all the time (from turning on to "freezing") - 13.06-13.07 V (specs require 13 V).

[ztrekr]

Re: 204B freezes after caps replace

Hooray, I've fixed it! I was right all along - EEPROM A81SC (24C08) got corrupted (probably due to the wild voltage swings because of bad caps).

So shorting pins 5 and 6 while turning the monitor on, cleared it and the monitor stopped freezing!

tom66, thanks for the info!