12 Jan
2008
12 Jan
'08
11:51 p.m.
Hi, all,
I've been collecting various classic bits to work on over the winter,
including a pre-CTRC 32K PET board (2001-N/3032) and a Static PET
board. I don't have any cases or accessories, but I do have a C2N232,
a single bare keyboard, and a C=Key converter enroute. For video, I
was planning on trying that ancient XOR circuit to make composite video
from sync and video, and feed that to an old Panasonic
mono CRT I saved
from scrap. What I'm lacking at this point is a power supply.
Obviously, I'm unlikely to find a suitable mains transformer, so I was
going to cobble up some form of switcher that puts out enough of the
right voltages to make this all work. Poring over the schematics for
the 2001-N board on zimmers.net (e.g. 320349-9.gif), I'm guessing that
the onboard regulator circuit is pumping out +5VDC at over 5A, +12VDC
at a couple of amps, and a miniscule amount of -5VDC. I'm not running
a real tape drive, so I'm not as worried about the +9VDC unreg.
Does anyone have any reasonable estimates or real-world measurements
for the current draw on the various supply lines? Has anyone out there
ever gotten a PET to run from externally regulated DC?
Thanks,
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 12-Jan-2008 at 23:30 Z
South Pole Station
PSC 468 Box 400 Temp -13.9 F (-25.5 C) Windchill -32.7 F (-36.0 C)
APO AP 96598 Wind 8.3 kts Grid 23 Barometer 686.2 mb (10395 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
13 Jan
13 Jan
5:55 p.m.
Hi, all,
I've been collecting various classic bits to work on over the winter,
including a pre-CTRC 32K PET board (2001-N/3032) and a Static PET
board. I don't have any cases or accessories, but I do have a C2N232,
a single bare keyboard, and a C=Key converter enroute. For video, I
was planning on trying that ancient XOR circuit to make composite video
from sync and video, and feed that to an old Panasonic mono CRT I saved
from scrap. What I'm lacking at this point is a power supply.
I elieve the 8296D (internal floppy drives) PET used a switching supply.
Do any docs for that machine exist, I wonder...
Obviously, I'm unlikely to find a suitable mains transformer, so I was
Actually, I do have a 'spare' PET mains transformer somewhere, from
sombody who converterd a PET to the intenral drive model. The problems
would be (a) getting it to you and (b) it's the 240V-input version, and
(c) finding the darn thing.
You could consider winding the transformer. You can get 'transformer
kits' I believe that come with pre-wound primary windings to suit mains,
and a set of laminations. You wind the secodnaries (the instructions tell
you how many turns/volt to use) with suitable wire and put it together.
Said kits come in differnt total power ratings, either work out the total
power used by the PET, or estimate it from the size of the origjnal
transformer.
-tony
10:22 p.m.
On Sun, Jan 13, 2008 at 05:55:28PM +0000, Tony Duell wrote:
Well... we are getting down to the end of the season here, so things
sent from this week onward have a decreasing chance of arriving before
the last plane.
Ethan Dicks wrote:
> Hi, all,
>
> I've been collecting various classic bits to work on over the winter,
> including a pre-CTRC 32K PET board (2001-N/3032) and a Static PET...
I elieve the 8296D (internal floppy drives) PET used a
switching supply.
Do any docs for that machine exist, I wonder...
Interesting. I can check zimmers.net when I'm connected to the 'net
tonight.
Obviously,
I'm unlikely to find a suitable mains transformer, so I was
Actually, I do have a 'spare' PET mains transformer somewhere, from
sombody who converterd a PET to the intenral drive model. The problems
would be (a) getting it to you and (b) it's the 240V-input version, and
(c) finding the darn thing. You could consider winding the transformer. You can
get 'transformer
kits' I believe that come with pre-wound primary windings to suit mains,
and a set of laminations. You wind the secodnaries (the instructions tell
you how many turns/volt to use) with suitable wire and put it together.
Said kits come in differnt total power ratings, either work out the total
power used by the PET, or estimate it from the size of the origjnal
transformer.
I have plenty of time to wind a transformer, but I probably don't have
time to get a kit like that in. I don't happen to know the exact power
draw of a PET board - according to the 2001-N/3032 schematic on zimmers.net,
there are a pair of LM340s for +5V, a 7812 for +12V, and a 7905 for -5V,
but then off of the transformer, there's a tap for AC for the monitor
(which gets immediately regulated down to +12V with a local 7812), and
the cassette motor is powered by switched unregulated +9V, tapped off
between the bridge rectifier and the LM340s. I don't plan on running a
_real_ cassette drive, but I think the latest versions of the C2N232
can use MOTOR-ON as another input line, so I'll need some small amount
of power for the motor circuit.
To get rolling, I was planning on building either the NAND-4066 or the
XOR video circuit that's been floating around for decades, then directly
connect a couple of bench supplies past the regulators which will give
me the benefit of being able to sample the current draws while
simultaneously running the board. I don't have a keyboard here yet,
but I did just receive the C=Key, so I can build that up and get a
PET-friendly keymatrix downloaded to it. After that, it's just a
packaging and storage-device issue.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 13-Jan-2008 at 22:10 Z
South Pole Station
PSC 468 Box 400 Temp -14.6 F (-25.9 C) Windchill -38.4 F (-39.1 C)
APO AP 96598 Wind 13.4 kts Grid 33 Barometer 687.6 mb (10343 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
14 Jan
14 Jan
11:18 p.m.
_real_ cassette drive, but I think the latest versions
of the C2N232
can use MOTOR-ON as another input line, so I'll need some small amount
of power for the motor circuit.
I thought that the Motor-On signal was just a swtich to ground inside the
tape recorder that signaled to the PET that the play or record keys had
been pressed. IIRC it goes to a TTL-level input somewhere. It's
independant of the actual motor control circuit, which IIRC is a power
transistor connecting the unregulared 9V line to the motor.
About 20 years ago (is it that long???) I built an interface between a
PET casstte port and a Radio Shack tape recorder, The recorder i used had
the useful design feature that the internal power switch (operated by the
keys on the recorder) was 'before' the remote control socket. That means
I could use a relay conencted to the socekt to control the motor (relay
coil driven from the motor drive output on the PET) and could sense the
power voltage on one side of that socket wrt ground (outside of the audio
sockets) to determine if the keys were pressed. So my interface worked
just like a real CBM tape unit.
I should still have the scheamtics, etc for that, but they will take some
finding...
-tony
6197
days inactive
6199
days old
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