I would guess the lower voltages are generated from a switcher off the 85 or 42 volt lines.
First check with an ohm meter in those lines to look for a dead short. Dwight ________________________________ From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Philipp Pap via cctalk <cctalk@classiccmp.org> Sent: Tuesday, May 9, 2017 6:26:43 AM To: michael.new...@gmail.com; cctalk@classiccmp.org Subject: Re: HP Draftmaster RX pen plotter needs love Hi Michael, dear board Did you solve your power supply problem? My Draftmaster I did work for 1 hour, I did even manage to do a demo plot. Then it died, right before my eyes the display got brighter and brighter and now - nothing when powering on, except a humming sound. I think that I’m responsible for the dead, as the plotter stood in an attic for 20 years, meanwhile power was raised from 220 to 230v (+-10%) in Europe. I realized that the input power can be adjusted between 220 and 240v at the power inlet of the plotter (on the top there is a small stage for a screwdriver, then the cover opens and the rotating think can be taken out)!! Anyhow, now I have 41 and 83 Volts at the 42 and 85V test points, but always 0 Volts at the +5,-12,+12,+15V test points. The fuses are good and the secondary transformer seems good as well. Right now I am waiting for an esr-meter to test the capacitors, any clue would be extremely helpful for me! With nice greetings Philipp PS: tinkering with this masterpiece of engineering is fun, but now my back hurts, but it is worth it
