Proview Pro576 (Model 568) delays to start when cold.

[EGuevarae]

I have a Proview LCD 568 that has no bad caps on a visual inspection, but it delays to start on cold. Checking my notes, all the caps are su'scon (in the bad list), so maybe your problem is similar to mine. I had this since the beggining of the last year, and I had forgotten about it when I was cleaning this morning and found it. I didn't open it again, but went straight to my notes. On them, I saw that (as mentioned) all the caps are su'scon. It has:
07 - 220uf 16v
03 - 22uf 16v
07 - 100uf 16v

All are Su'Scon @ 105C (no series. I was not aware of such things back then).
The problem with the monitor is : When it is turned on after being off for a while, the power led starts blinking and if you press the On/Off button, it won't respond. After a while, the screen starts up and you can turn it on/off and it works perfectly, until you let it off for a while (an hour and a half is enough). If I disconnect the ribbon from the VBoard to the LCD Panel, the power led goes to solid green as soon as you press the ON button, even if cold. The behavior is present only with the LCD panel actually connected to the VBoard (according to my notes). The PSU is an external 12v 3.5a brick, and besides the VBoard, there is only a standalone inverter (not same board). I have tested the inverter using a 12v PSU (a cable adapter from an unused ribbon and an extension for a molex cable of a n ATX PSU) and it starts OK everytime. Any suggestion?
Will dissasembly the LCD tomorrow and will take pictures to post if necessary.
Eduardo

[PCBONEZ]

Re: Proview Pro576 (Model 568) delays to start when cold.

It sounds like one of those caps is responsible to charge up to a point to turn on a transistor and for whatever reason after a full discharge that cap is taking too long to charge up.
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Might be the cap itself or might be a degraded resistor or diode in it's charge/discharge path that is either restricting the charge path or opening up a discharge path that shouldn't be that large during start up.
.

[PCBONEZ]

Re: Proview Pro576 (Model 568) delays to start when cold.

I'm working on a Proview power board/inverter out of a TV right now.
I'm not real impressed.
It is silk screened for two fuses and both fuses are missing with soldered in jumpers installed in their place.
.

[FIXITNOW]

1

[FIXITNOW]

Re: Proview Pro576 (Model 568) delays to start when cold.

I HAVE KNOW THE PSU external 12v 3.5a brick to be faulty voltage kept droping so i replaced it

[Wizard]

Re: Proview Pro576 (Model 568) delays to start when cold.

Don't keep using the unit till capacitors are replaced and install fuses.

Cheers, Wizard

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

Don't keep using the unit till capacitors are replaced and install fuses.

Cheers, Wizard

That was my original plan, but the caps I have will not clear the tight space. I will post a pic of the board so you can see them. They have no vents, and all of them look OK. I suspected when I checked my notes, that the panel turned on after a cap charged fully, but which one (or ones)?
My 2nd idea was to change them one by one until I found the culprit instead of buying the whole set from Digikey (I would really be happy to change only the bad ones instead of all, just for the sake of knowing which were bad)

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

I HAVE KNOW THE PSU external 12v 3.5a brick to be faulty voltage kept dropping so i replaced it

One of the first things I did. I took a good known, working brick from another Proview, and same result.

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

Here are some pics. You can see the Su'scon brand, and the size of the caps.

[PCBONEZ]

Re: Proview Pro576 (Model 568) delays to start when cold.

What is with the missing cap with a circle around the spot?
Did you pull that or is one just missing there?

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

What is with the missing cap with a circle around the spot?
Did you pull that or is one just missing there?

It was not there (it looks like never was anything there) when I opened the LCD the first time. But there was almost shorted by solder, so I did that and circled it (but I don't remember why the circle ;-)

[PCBONEZ]

Re: Proview Pro576 (Model 568) delays to start when cold.

It just looks like some cap has been removed there in the pic.
Disturbed solder and a circle.

.

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

It just looks like some cap has been removed there in the pic.
Disturbed solder and a circle.
.

Yeah, but believe me, it was nothing there. There are many silk screened components including a ribbon-like screen that reads LVDS (never heard of LVDS outside of SCSI HDDs ....), but nothing is present.
And in the end, it was a cap, or all of them. I tested with the caps I had to see if it will work before ordering from Digikey, and guess what? It worked right since the first time after the recap. Now I just have to order, wait for the order and solder the ones that will be finally there, and that's it.
Now I am a happy owner of a Proview 568. See the pics of the "after".

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

Look, I found someone with my same problem, but on a 17". Now I'm stuck looking for 5mm tall caps.
Xerox Thread

[Krankshaft]

Re: Proview Pro576 (Model 568) delays to start when cold.

Glad you got it working it's times like that I'm glad I have an ESR meter.

The warm up working is a common symptom of a cap whose ESR has gone up as temperature rises ESR drops so once the monitor was warm the caps ESR was low enough for the monitor to function.

However when it was allowed to cool the ESR rose again causing the problems you encountered.

Whenever a problem is temperature related like that I always go for the caps first.

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

I'm learning new things in this forum. Honestly, I received basic electronics instruction as part of my Computer Maintenance & Repair course 15 years ago, and beyond what components are/do, and soldering skills I acquired when I made (a lot of) null modem cables. But apart from that, only reading and browsing on the forums gave me the "I can do it" idea, and thanks to people like you (PCBONEZ, Krankshaft, Wizard and all the other users/members who contribute here whose names escape my troubled mind right now... I might have cap problems myself ) I am learning. I have saved so far like 15 LCDs from the landfill, and I'm proud of that. And I'll be prouder if I can find those 5mm caps.......
And yes, an ESR meter should have saved lots of time & frustration , but then again, all Su'scon would have to go anyway for the repair/recap to last, or am I wrong?

[PCBONEZ]

Re: Proview Pro576 (Model 568) delays to start when cold.

I finally figured out how to get Mousers search to kick that back but I forgot who asked.

You can get 5mm tall 85C in 22uF and 100uF in Xircon L Series at mouser.

http://www.mouser.com/Search/Product...nIWGBVXQ%3d%3d

http://www.mouser.com/Search/Product...Xm8vRJ0w%3d%3d

L Series:
https://cdn.badcaps-static.com/pdfs/...e75ba3d0e2.pdf



If you can squeeze in 7mm you can get the same in 105C Xircon MLRH series.

http://www.mouser.com/Search/Product...H2nu4UdQ%3d%3d

http://www.mouser.com/Search/Product...agTxckjA%3d%3d

Xircon MLRH series data sheet shows a 7mm tall 220uF 16v but mouser doesn't list it.
https://cdn.badcaps-static.com/pdfs/...32fd3c9b57.pdf

[EGuevarae]

Re: Proview Pro576 (Model 568) delays to start when cold.

I ran into those (first link) but as they were 85c rated and the original were 105c, I didn't pay attention to them (I searched Digikey, and then Mouser). But now that I think about the issue, as the power supply is external, and the inverter is on a separate board, I guess heat would not build up that much, and you can use 85c. Also, as the board is feed 12v 3.5a, I think I can safely use 16v caps. I know that you should go to same V rating or higher, but in this case, 12v is the only voltage used (well, there is 5v too, but it is safe with 16v also), so you can go to 16v and have room for the unexpected (a 4v tolerance). Am I right?

[PCBONEZ]

Re: Proview Pro576 (Model 568) delays to start when cold.

Actual circuit voltage + ripple voltage must be less than cap's rated voltage.
As long as it is you are okay on that.
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If there is an SMPS section on the board then the voltage (or some of them) may be higher than what it's feed. If there is no transformer you are probably okay but it's still best to check with a meter to be 100% sure.

.

[PCBONEZ]

Re: Proview Pro576 (Model 568) delays to start when cold.

Oh DUH!
You posted photos...
I see a transformer in there.
I would check voltages.