HP Draftmaster RX pen plotter needs love
elson at pico-systems.com
Tue May 9 11:10:18 CDT 2017
On 05/09/2017 08:26 AM, Philipp Pap via cctalk wrote:
> 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.
Does this have a switching power supply for the logic (5,
12, 15V) or is it a rectifier/filter/regulator off the
If rectifier/filter/regulator, it seems odd that FOUR
voltages would quit at once. So, I'm guessing it might have
a switching supply for those voltages. It sounds like the
regulation circuit failed (display got brighter) and then a
crowbar circuit tripped to shut it down. Unless you are
pretty skilled, switchers can be a bit hard to
troubleshoot. It might be easier to get a supply with the
needed voltages and just patch it in.
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