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Aopen/Acer AP43 - need VRM info

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First post, by quicknick

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Hi folks,

Got this board today:

http://jippel.de/boards/board22-1.jpg

Well, not my photo but it's identical. It looks almost brand new, and i love its looks and the way that it seems more advanced than the usual boards from the era (SOIC instead of DIP chips, SMD and even a few that look like solid electrolytic capacitors). Just that someone before me had to harvest all the jumpers, the battery socket and the VRM!
Thanks to the manual found on the net i was able to set the jumpers for a DX-33 which works great, but for 3.45v CPUs i will need to solder a VRM and i have no idea what was originally in that place. So i kindly ask anyone that got this board to check and tell me the VRM type (i think there is a heatsink on it which might have to be removed, but from the pic it seems a simple clip-on).

Thanks!

Reply 1 of 8, by Deksor

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If nobody answers until this week-end, I'll try to find the time to take a picture of mine

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Reply 2 of 8, by Deksor

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Whoops, sorry for the late answer, I took the photo yesterday and completely forgot about posting it ^^

There you have it !

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Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 3 of 8, by PCBONEZ

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@ quicknick
Those are most likely just wet lytics in SMD cans.
Solid Poly caps cost in the vicinity of $20 each in the 90's so they were rare outside of server equipment or very high end.

I'm not sure what you are trying to do. You want to change the LDO Regulator?
I fiddled with Deksor's photo and I can read that one is an LT1085CT.
http://www.analog.com/media/en/technical-docu … =www.linear.com

I don't know the circuit or for sure but I suspect all you have to do is change the biasing resistors.
That's basically what happens when you use different jumper settings for voltage on boards like that.
.

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Reply 4 of 8, by quicknick

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Deksor - Thank you very much, really really appreciate your effort! I happen to have one LT1085 in my parts box, bought it for installing it on another Socket 3 board (TK8948F) but i had no time to fiddle with that. And now it will go on the AP43.

PCBONEZ - I'm not trying to mod anything, it's just that my board is missing some components (someone took them out), among them is the VRM. So until now i could only test it with 5v CPUs, and it works fine. Thanks for the advice and the info about capacitors, i wasn't very sure that they were solid, now i know they aren't 😀

Reply 5 of 8, by quicknick

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After fitting the missing parts (minus the molex plug, for which i have no use) and a mandatory BIOS update, the board works fine with an Am5x86-133. I was even able to run Landmark, Norton Sysinfo and Speedsys at 160MHz (but Topbench crashed with a divide overflow). Thanks again for your help!

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Reply 6 of 8, by PCBONEZ

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This might be a non-issue for that board because I dunno the actual purpose of the molex connector.
If it's used for power IN to the board it could be important.
If it's power IN then it is backing up the power from the AT power connector which is done to reduce the current load through the traces on the board.
If my guesses are right you might fry a trace or two by not using it.
.
That's a nice board. Wouldn't want that to happen.
.

GRUMPY OLD FART - On Hiatus, sort'a
Mann-Made Global Warming. - We should be more concerned about the Intellectual Climate.
You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.

Reply 7 of 8, by Eleanor1967

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PCBONEZ wrote:
This might be a non-issue for that board because I dunno the actual purpose of the molex connector. If it's used for power IN to […]
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This might be a non-issue for that board because I dunno the actual purpose of the molex connector.
If it's used for power IN to the board it could be important.
If it's power IN then it is backing up the power from the AT power connector which is done to reduce the current load through the traces on the board.
If my guesses are right you might fry a trace or two by not using it.
.
That's a nice board. Wouldn't want that to happen.
.

That molex is just a fan header on this board.

Reply 8 of 8, by PCBONEZ

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No worries then.

GRUMPY OLD FART - On Hiatus, sort'a
Mann-Made Global Warming. - We should be more concerned about the Intellectual Climate.
You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.

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