Schematic for Compaq Portable II please ?

[zippysticks]

Hi,

anyone have a schematic for this machine please ?
Particularly interested in a diagram for the power supply.

Photo of the offending article below - the eagle eyed among you might spot that resistor R21 (bottom right corner) has got very hot and burned its covering off.

 

[Trapani]

It's 22 ohm. I just looked it up.
I happen to be in what looks like exactly the same circumstances as you (Portable II)

There's a guy online who has photographed the boards of running machines which is extremely helpful as in the case of this resistor, one can reference the color bands

Compaq Portable II - Old Crap Vintage Computing

Wikiseasip.info (HDD configuration)

oldcrap.org

It's red red black gold, which would indicate 22 ohm
I suspect it's actually the tantalum upstream (orange guy to the right) that has gone bad. (15uf @25v)
When these go, they typically short which would transfer all the power to that resistor, and boom, low wattage resistor maek smok.

Will update if this brings old boy back online

 

[Trapani]

Got it DONE. She's alive once again

 

[mikerofone]

Hi zippysticks and Trapani,

just chiming in that I just repaired my Portable II which had the exact same problem. It still turned on but something smelled burnt after 2-3 seconds, and I eventually spotted that the same resistor was quite crispy, but still measured a perfect 22 ohms. The tantalum cap next to it measured 20-30 ohms DC - not a dead short, but enough to cook that poor R21. Replaced the few tantalum caps on the board and R21, and it's been working well since!

Maybe it'll be of help to someone in the future: I found this Vogons thread useful, though my European PSU board and the one in there had some different cap values and placements.

Thanks again for your post and documenting the success of your repair! It boosted my confidence that I found the right problem.

Cheers
mikerofone