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Old 04-18-2010, 12:22 AM   #1
pedro
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Exclamation Acer AL1715, Delta ADP-40AF power board

This monitor was heading for landfill, owner re-routed it to me. Case showed signs of a prior (and ROUGH) entry. Described symptoms - "no pic".

Tested, and main (video) board function OK, flashlight showed desktop after logo. No backlight attempt. Ripped open and found Delta board, same as in thread http://www.badcaps.net/forum/showthread.php?t=5447

All 2SC5706's checked OK, no real hotspots, all caps (LTEC) showed no leaks/bulging and ESR's acceptable. No circuit found but similar enough to others which use 4x2SC5707 and two transformers.

Then I spotted the problem - the solder joints on the 6-pin inter-board connector had fracture lines on three of them. I'll attribute it to the previous entry (or the original fault occasioning it), as I'm a *lot* more careful than that. Resoldered, reassembled, now in burn-in.

I'm only posting this to remind people to not over-think fault-finding. I've been doing LCD montors for a while, and other servicing for waay too long, and every so often the fault is trivial but not found following the well-beaten path of experience.
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Old 04-18-2010, 11:41 AM   #2
PlainBill
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Default Re: Acer AL1715, Delta ADP-40AF power board

Quote:
Originally Posted by pedro
This monitor was heading for landfill, owner re-routed it to me. Case showed signs of a prior (and ROUGH) entry. Described symptoms - "no pic".

Tested, and main (video) board function OK, flashlight showed desktop after logo. No backlight attempt. Ripped open and found Delta board, same as in thread http://www.badcaps.net/forum/showthread.php?t=5447

All 2SC5706's checked OK, no real hotspots, all caps (LTEC) showed no leaks/bulging and ESR's acceptable. No circuit found but similar enough to others which use 4x2SC5707 and two transformers.

Then I spotted the problem - the solder joints on the 6-pin inter-board connector had fracture lines on three of them. I'll attribute it to the previous entry (or the original fault occasioning it), as I'm a *lot* more careful than that. Resoldered, reassembled, now in burn-in.

I'm only posting this to remind people to not over-think fault-finding. I've been doing LCD montors for a while, and other servicing for waay too long, and every so often the fault is trivial but not found following the well-beaten path of experience.
Good job troubleshooting!!!

This reminds me of a couple of situations I encountered about 20 years ago. At that time I was teh Lead Technician in the production test area of a major manufacturer of commercial modems. One method of rating our technicians was on their productivity. One guy let the system beat him, another figured out how to legitimately beat the system.

'Joe' was very proud of his theoretical electronic knowledge. He insisted on knowing the intimate details of the design of any card he worked on. He could take measurements and within 10 minutes isolate the cause of just about any failure. He had great scorn for the other techs (he referred to them as 'eye techs') who would spend 2-3 minutes looking for manufacturing defects (reversed IC, solder short, etc) before even plugging the card into the test fixture. Of course, 'Joe' failed to realize his productivity was well below that of the 'eye techs'. As a result he was stuck in grade well after the other techs had gone on to cushy jobs as a field service tech.

On the other hand, Ron would spend the first half the day testing cards. If they failed, he gave them a cursory exam for common problems, noted the test they failed, and went on to a new board. Buy lunch time he had met - or exceeded - the average day's productivity. The rest of the day he would spend troubleshooting cards. When he fixed one that had failed at a particular step, he would check at the other boards that had failed at that step; if they had the same defect, he had a some easy fixes. In general, his daily output was DOUBLE the average. He wound up promoted to a job with much better pay and (responsibility).

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