Acer AT2602 Sound, but no display

[Vasco34]

Hi all, this is my first post on Badcaps, so will endeavour to list as much information as I can and respond with details as need to help fix my issue. Ok, firstly about me and my limited electronic experience. I first gave re-capping a go about a month ago, when I purchased about 10 Dell optiplex GX620 SFF as “salvage” units. Did some hunting on the net, found out that these were plagued with bad capacitors (both on motherboards and power supplies) and was able to fix them, no problem.. also did a re flow on an Acer 5520g laptop (typing this post on it now) and a Geforce 8800GTX video card. So in short I'm no master on electronics repair, but have given it a go with success. However I thought I would give Flat panel TV's a go, as I have seen that these also had issues with bad capacitors and assumed that I could spot the caps and replace and have a cool/cheap LCD or plasma for the “games room”.
As you can tell from me writing this post, it is not the case. Ok the details for now and i'll add some images as requested.

TV is an Acer AT2602
Symptoms: TV turns on with sound and backlight, no picture. After about 5-6 min (from cold start) image appears, I think everything is cool. Then 5-6 min's on the image freezes and fades RED – Black and I'm back to just sound and back light. Sometimes after a period the image will return, but quickly freeze again as described above.
What I have done is go with what I know, and that is replacing caps. Now on opening the TV, there were no signs of bulged or leaking Caps, but as I have read, this does not mean they are not bad. So I have started with the Power supply board and replace all CAPs on the secondary side of the board. That done I'm still in the same situation, which I was kind of expecting, but thought best to eliminate those. I have tested all power outs and these relate to the voltage values printed on the power board. It's obvious that something needs to warm up to get the image going so possibly a dry joint on the board. I tried to isolate this, by on a cool start using a heat gun to warm up an area at a time but it just switched itself off, maybe a temp sensor cut the power.

I am hoping that someone may be able to point me in the right direction on where to look to help resolve this problem.

Photo descriptions

PA320127 = TV off
PA320130 = Power on, sound working, no picture, back light on
PA320131 = after 5 mins screen shows picture (all good)
PA320132 = switched TV off and back on still all good
PA320136 = changed input mode, still ok
PA320138 = some time into screen working imge would freeze and fade RED - black (sound still working)
PA320139 = sound still working, picture completely gone, back light only.

Cheers

Vasco

[PCBONEZ]

Re: Acer AT2602 Sound, but no display

First, in the last pic, with back light only the screen would be white.
A black screen [with it on] is either no back light -or- the signal isn't getting all the way to the screen [the graphic chip IS sending and it's getting to the screen but there is no 'data' in what it's sending.]

Yes. Caps can be bad without bloating at all.
Symptoms DO strongly suggest a caps issue mucking up the power although other problems could do it too.

These things often have poor soldering - especially on the pins of large parts like the transformer[s].

Usual first steps are to:
- check all the soldering for cold joints and re-solder if needed.
- make sure all the caps are good. [Which might mean replacing depending on your situation with test equipment.]

I'm not a guru with these yet, but I'm here, and that is what the gurus will tell you to do first.

.

[retiredcaps]

Re: Acer AT2602 Sound, but no display

What I have done is go with what I know, and that is replacing caps. Now on opening the TV, there were no signs of bulged or leaking Caps, but as I have read, this does not mean they are not bad.

What caps did you use for replacement?

Please post clear focused pictures of your boards so we can see what it looks on the inside.

[Vasco34]

Re: Acer AT2602 Sound, but no display

What caps did you use for replacement?

Please post clear focused pictures of your boards so we can see what it looks on the inside.

I have used

4 x PANASONIC EEUFK1C102 16V, 1000UF
1 x ILLINOIS CAPACITOR 477KXM035M 470UF, 35V
1 x ILLINOIS CAPACITOR 108CKH035M 1000UF, 35V
1 x MULTICOMP MCRH35V337M10X16-RH 330UF, 35V
1 x ILLINOIS CAPACITOR 227CKR025M 220UF, 25V
1 x PANASONIC EEUFC1A102 1000UF, 10V
1 x RUBYCON 10ZL680M8X16 680UF, 10V

I'm having issues with uploading photos at the moment. I will try again later.

Cheers

Vasco

[PCBONEZ]

Re: Acer AT2602 Sound, but no display

1 x ILLINOIS CAPACITOR 108CKH035M 1000UF, 35V -- Not Low ESR
1 x MULTICOMP MCRH35V337M10X16-RH 330UF, 35V -- Not Low ESR
1 x ILLINOIS CAPACITOR 227CKR025M 220UF, 25V -- Not Low ESR

[Vasco34]

Re: Acer AT2602 Sound, but no display

Thanks for the responses.

I'm going to replace the above with these:

PANASONIC EEUFK1V102L 35V, 1000UF
UNITED CHEMI-CON - EKMG630ELL331MJ20S 330UF, 65V
RUBYCON 35ZLG220M10X12.5 220UF, 25V

What ESR value should i be aiming for?

Cheers

Vasco

[PCBONEZ]

Re: Acer AT2602 Sound, but no display

The proper thing to do is look up the data sheets for the old caps then get that ESR [sometimes says Impedance] or lower.
If they are GP caps ESR won't be listed in the data so use the Ripple rating and get caps that handle the same or higher Ripple.
[[Same ESR or less.
[[Same Ripple or more.
-or- (for GP)
What I [and many others] do for GP caps is to get 'entry level' low ESR caps like Panasonic FC, Nichion PW, Chemicon LXZ or similar. The cost difference is about nil and they are better caps.

If you aren't looking up the old specs then you are guessing what needs the be there.

KMG are not low ESR either.
Look at the data sheet. - ESR/Impedance is not listed.
If the ripple is higher than the original caps they will be fine though.

Also when you compare new to old specs watch what frequency they used when they show ESR/Impedance. The standard frequency is 100kHz but some caps are done at other frequencies. If the frequency is different you can't compare ESR without doing a bunch of math. Frankly it's usually easier just to get caps spec'ed at 100kHz in the first place.

.

[PlainBill]

Re: Acer AT2602 Sound, but no display

Another thing to remember about ESR is it's a 'better than' spec, just like the endurance spec. As an example, the Panasonic EEU-FC1C681 is rated at an ESR of .068 ohms and an endurance of 3000 hours at 105°C while the Panasonic EEU-FM1C681 is rated at an ESR of .026 ohms and an endurance of 4000 hours at 105°C. If you measure the ESR of a new EEU-FC1C681 it is designed to be below .068 ohms; it could be much lower, even below .026 ohms and still meet specs. After 10,000 operating hours at 50°C the ESR of both caps may have risen by 50% and still be within spec while the Lelon equivalent or a Panasonic 85°C general purpose cap would have vented.

You can waste too much time trying to match the ESR of the original cap, especially since a major criteria used to select the Capxon, Lelon, or Elite original was the cost. At the same time one factor that is often ignored is the dimensions. The best ESR and endurance specs are meaningless if the replacement works, but you can't get the back on the TV.

PlainBill

[Vasco34]

Re: Acer AT2602 Sound, but no display

Hi Guys, thanks for the responses.. WE have success!! not without a lot of stress and confusion though!

I replace the caps that mention above, fire up the TV, took about a minute to flick on. Played a full DVD (1-2hrs) and the TV shown none of the freezing symptoms as described in my first post. I let the TV continue to be on for an additional 2 hours, still working fine. I figured that it was fixed and screwed the TV back together and moved it into the lounge to try it again, after being off for half hour or so. After about a 1-2 minute warm up, it was back on and was on pretty much all night with no faults. Left it off over night and turned it back on in the morning and it was back to its little games of take 10 min to show an image and the freeze up within 5-6 mins.. Frustrated, i took the TV apart again, removed the power board and searched the back of the board for anything that looked like suspected soldering.. Had my brother (electrical engineer) come around with a fresh set of trained eyes and we added some extra solder to a couple of points and gave it another go.

Worked.. again only for about 5mins and froze again! As my brother was inspecting the DVI cable, he lent on the top of the TV frame and the picture return! As he took pressure of it froze again! Pressure on the frame, it worked again. He figured it may be a bad earthing point and suggested to go through and ensure all screws where in and tight. Fix the back on... and it’s a working Tele again.. However it has froze once in the past 2 days, but a simple push on the opposite diagonals of the TV frame return the picture and running well..

I know that it’s not a complete fix because I have not isolated the issue on where the problem point is, but after what I’ve been through with it I’d say is good enough victory, until it really plays up and I have renewed patients.

Cheers and thanks again.

Vasco