Acer AL1917 restarting

[Behemot]

Re: Acer AL1917 restarting

Tried CCFL from the other display, still restarting, seems that problem is in the inverter itself.

Will ask friend of mine for camera, I left mine at home and as you see withotu camera it would be difficult to take pictures

[Behemot]

Re: Acer AL1917 restarting

Here are the images finaly, if you can advice comething from it, would be cool

ATM, there are some caps recapped, some original as I tried if the problem is not in in too low ESR of replacements and so

[Rtech]

Re: Acer AL1917 restarting

The two Mosfets fail regularly on DAC Boards,and thats probably the problem.

[Behemot]

Re: Acer AL1917 restarting

Those DIP-8 chips? They're actually the lately comon two-transistors-in-one-package? I haven't checked them, thought they are some drivers actually

[Rtech]

Re: Acer AL1917 restarting

Chances are it is them.

[Lumberjack777]

Re: Acer AL1917 restarting

These boards also have SMD fuses on the bottom. Check the one I circled in red, and any others you might find on the bottom.

[selldoor]

Re: Acer AL1917 restarting

You also need to remove that yellowing glue

[Behemot]

Re: Acer AL1917 restarting

You also need to remove that yellowing glue

Isn't it there like additional protection against high-voltage short? It is not any way burned to be conductive.

[selldoor]

Re: Acer AL1917 restarting

Chances are it is them.

Id vote for them as well

See here

https://www.badcaps.net/forum/showpo...&postcount=204

has restarting problem also, but cant read what chips you have and you did not say.

[sabre504]

Re: Acer AL1917 restarting

If memory serves they should be AOP605

[selldoor]

Re: Acer AL1917 restarting

Isn't it there like additional protection against high-voltage short? It is not any way burned to be conductive.

You are right I thought it was white turned yellow - next step would be brown and conductive but it was never white on closer look it is a sort of semi see through lacquer. - sorry.

[Behemot]

Re: Acer AL1917 restarting

Bot FETs as well as all fuses are fine.

[selldoor]

Re: Acer AL1917 restarting

Just curious, what voltages do you get across the

1) big filter cap? Is it stable?
2) little startup cap? Is it stable?
3) 5V SB?

when the problem happens?

Did you check these? I was trying to look for the startup cap but you have clipped the picture?

Can you try with it all connected up but with the ribbon cables to the lcd panel disconnected

[Behemot]

Re: Acer AL1917 restarting

Have you even read the thread? It works fine without CCFLs connected. Tried backlight from another display, same behaviour.

Voltage accross input capacitor is good. Problems persist no matter what capacitors I use so here is not the problem, the original ones were not the soruce of the problem. Everything now leads me to bad inverter transformers.

ADD// I've replaced input cap with no change. If it helps anything, I hear strange buzzing for all the time, except when it turns off. It comes from the main transformer.

If I disconnect one of the CCFLs on the B/W cable side, the other flashes for a fraction of second, but it seems the whole power supply stays turned on. So can it be bad transformer after all? It may be some problem on primary when the rectifier and fuse were blown, right?

[Behemot]

Re: Acer AL1917 restarting

I think I have found the problem. When changing one small capacitor, I have burned tiny path near to it. I have connected the cap to one joint of the path but didn't notice it was actually interconenction between two parts of some circuit. After joining it with piece of wire, it behaves more normally. Now I need to get some VGA cable to test it

ADD/ oh, here is one in a drawer

[selldoor]

Re: Acer AL1917 restarting

Behemet - can you recall where the damaged trace was - perhaps mark it on a picture?
There are a couple of threads with restarting problems so might be relevant.

[Amraks]

Re: Acer AL1917 restarting

I just realized what u was doing selldoor thanks.

I hope it was the 220uf 50v cap trace.

[Behemot]

Re: Acer AL1917 restarting

Behemet - can you recall where the damaged trace was - perhaps mark it on a picture?
There are a couple of threads with restarting problems so might be relevant.

It's on the picture 4 of 5, bottom left corner with the SSOP-8 chip. You see there is the bad soldering with crystalized dump of solder, several centimeters north from the chip in them iddle between three SMD diodes? That's where I've burned the trace. As the problem was with el'cheapo PCB combined with my 125W soldering pistol, I think it is not usual actually

[selldoor]

Re: Acer AL1917 restarting

Thanks for that - just to be sure - you mean the area in the yellow box?
Surprised with a 125W there wasnt a hole right through
Amraks has a similar problem - destroyed the same trace - I think.

[Amraks]

Re: Acer AL1917 restarting

both sides are destroyed.

so negative side.

wondering were the negative side leads too.