9 May
2017
9 May
'17
9:26 a.m.
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
9 May
9 May
12:10 p.m.
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
transformer?
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.
Jon
2:23 p.m.
Am 09.05.2017 um 18:10 schrieb Jon Elson <elson at
pico-systems.com>:
On 05/09/2017 08:26 AM, Philipp Pap via cctalk wrote:
Jon
Could you please have a quick look at the photos here
https://goo.gl/photos/m5qW1bz8kSujfK7J8 as I?m way under your skill level.
Does this look like rectifier/filter/regulator or a switching supply?
A complete schematic would make things simpler.
Thanks!!!
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 transformer?
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.
Jon
2:29 p.m.
Am 09.05.2017 um 18:10 schrieb Jon Elson <elson at
pico-systems.com>:
On 05/09/2017 08:26 AM, Philipp Pap via cctalk wrote:
OK, I just read in the service manual
?The power supple is a switching type dc supply incorporating a pulse-width modulator
(PWM).?
but I don?t know the meaning on the drawing ?+5V ref? ?vcc? ? POWER ON ??~RESET , HALT,
RESET?
Could that mean that the problem could be in this ?POWER ON? block logic???
Thanks again!
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 transformer?
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.
Jon 
8:10 p.m.
Is there 42 Volts on both sides of the 42V fuse? Seems odd that there's 42V to the
switcher but no voltage at the other end but the fuse is intact. Normally when the
switcher blows, the main switching transistor shorts and takes out the supply fuse.
The power supply transistors are on the black heatsink near the transformer with the
yellow label. I'd be checking those to make sure they are OK using a transistor
tester or multimeter on the 'diode' setting. I'd also check nearby diodes and
transistors to make sure they are OK as well. Tricky without a schematic that's for
sure.
I have an RX that powers up but don?t have access to it until the weekend but I could try
to assist with voltage checks to allow you to compare if that helps.
David Collins
HP Computer Museum
www.hpmuseum.net
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Philipp Pap via
cctalk
Sent: Wednesday, 10 May 2017 4:30 AM
To: Jon Elson <elson at pico-systems.com>
Cc: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: HP Draftmaster RX pen plotter needs love
Am 09.05.2017 um 18:10 schrieb Jon Elson <elson at
pico-systems.com>:
On 05/09/2017 08:26 AM, Philipp Pap via cctalk wrote:
OK, I just read in the service manual
?The power supple is a switching type dc supply incorporating a pulse-width modulator
(PWM).? but I don?t know the meaning on the drawing ?+5V ref? ?vcc? ? POWER ON ??~RESET ,
HALT, RESET? Could that mean that the problem could be in this ?POWER ON? block logic???
Thanks again!
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 transformer?
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.
Jon 
4:27 p.m.
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-bounces at classiccmp.org> on behalf of Philipp Pap via cctalk
<cctalk at classiccmp.org>
Sent: Tuesday, May 9, 2017 6:26:43 AM
To: michael.newton at gmail.com; cctalk at 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
2630
days inactive
2631
days old
5 comments
4 participants
participants (4)
-
david.collins＠dimensiondata.com -
dkelvey＠hotmail.com -
elson＠pico-systems.com -
philipp.pap＠gmx.net