Looking for HP Laserjet IIp+ power supply

Charles charlesmorris800 at centurytel.net
Wed Oct 31 17:14:29 CDT 2018


Actually I just fixed it ;) <Emily Litella> Never Mind.

I took the supply all the way apart and found one secondary filter cap that
had leaked electrolyte. Cleaned and fixed that, but still no luck. 155 volts
on the main filter cap. Then I noticed that occasionally it would try to
start for a blink but then the voltages would just drop to zero. So I
started looking around the section that had to be for bootstrap power to the
switching regulator, a common TL494 chip with datasheets online. Sure
enough, a small electrolytic on the primary side had blown its bottom out.
The diodes around it were still good. Changed that cap and a couple more
suspicious looking small ones and the voltages came right up (including the
24V once I pushed the cover-open microswitch).
Put it back in the printer, screwed it all together (a very modular design
for easier field servicing) and fired it up. Test page printed perfectly.
Saved some $ on a new laser printer. For now :)

I like these old cinder-block-sized (and weight) printers too. They last
ALMOST forever...

Charles 



More information about the cctech mailing list