17" LCD Monitor - PGE 1704B/LM1704

[tmcw]

Re: 17" LCD Monitor - PGE 1704B/LM1704

Just the VGA input on the board unfortunately.

Would any of those electrolytic caps on the logic board be involved with the VGA signal?

[tom66]

Re: 17" LCD Monitor - PGE 1704B/LM1704

Just the VGA input on the board unfortunately.

Would any of those electrolytic caps on the logic board be involved with the VGA signal?

Quite possibly... do you have a pic of the logic board?

[tmcw]

Re: 17" LCD Monitor - PGE 1704B/LM1704

Yes, I posted one earlier: https://www.badcaps.net/forum/showpo...55&postcount=6

I cut that down to maybe 25-30% before posting, but can make another in higher resolution if required.

[tom66]

Re: 17" LCD Monitor - PGE 1704B/LM1704

Yes, I posted one earlier: https://www.badcaps.net/forum/showpo...55&postcount=6

I cut that down to maybe 25-30% before posting, but can make another in higher resolution if required.

Darn - looks like a dedicated IC for VGA and scaler.

I'd replace all the caps around the chip, but I don't know what else to suggest except a new logic board.

[tmcw]

Re: 17" LCD Monitor - PGE 1704B/LM1704

Thanks for the help.

I replaced all but the 4 caps towards the lower right corner of the logic board, but the lines remain.

I suppose it's possible that the bad 12V (15.74V) could still be causing the vertical lines? There is a 13.07V going up to the TCON board, and if it's only supposed to be about 10V, could this cause the issue I'm seeing?

Or worse, that the overvoltage caused some damage in the logic board. So maybe I should go back to the powerboard and see if that can be sorted.

All I've done on the powerboard is replace the caps, and I took off the diode supplying the 15.74V, and it tested at 0.411 and OL, so I guess it's ok. What else is involved in generating the 12V?

I've had a quick look for a replacement logic board, but haven't seen any that are the same, most only have 1 ribbon connection.

EDIT: would it be worth getting a PC power supply, and connecting a 12V line up to the logic board instead of the 15.74V from the powerboard?

[Th3_uN1Qu3]

Re: 17" LCD Monitor - PGE 1704B/LM1704

The high voltages aren't going to the logic chip itself. The chip runs on 5v, 3.3v and 1.8v, the latter two being produced by those regulator ICs you said are okay.

Do replace the output caps of those regulators though. On a Bestview HD17A i've found a bad cap after the 1.8v regulator causing some really funky behavior.

[tmcw]

Re: 17" LCD Monitor - PGE 1704B/LM1704

Thanks, yes, I can see that now on the data sheet for the RTD2523.

I have replaced them though, although how important is it to use quality caps here? They were 220uF/6.3V Capxon originally, and I replaced most of them with some cheapos I had to hand, except the very first (the one before the first regulator), which is a Panasonic. All caps I used were new, so even if they aren't the best, shouldn't they be ok to use short term anyway?

The 3 smaller caps near the green speaker input, is it possible they're used in the VGA signal? I didn't change them.

[tom66]

Re: 17" LCD Monitor - PGE 1704B/LM1704

Thanks, yes, I can see that now on the data sheet for the RTD2523.

I have replaced them though, although how important is it to use quality caps here? They were 220uF/6.3V Capxon originally, and I replaced most of them with some cheapos I had to hand, except the very first (the one before the first regulator), which is a Panasonic. All caps I used were new, so even if they aren't the best, shouldn't they be ok to use short term anyway?

The 3 smaller caps near the green speaker input, is it possible they're used in the VGA signal? I didn't change them.

Ideally you should use low-ESR quality caps, but it shouldn't make too much of a difference for general decoupling. If it was the output of the switching power supply itself you would need to use low ESR caps.

Note down any numbers on the board and look on eBay for a replacement. If you take uncommon combinations you could get a lower price. For example, one PSU I replaced was 17PW22.2. Those were in the £20 - £30 range. So I searched for 17PW22 2 (no dot) and found someone selling one as 17PW22 v2 for £10 including postage.