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New toy: Tandy DMP 132 (26-2814) printer | |
August 03rd, 2023 | |
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Picked up a new toy from a local e-waste recycler: A Tandy DMP 132 | |
(catalogue number 26-2814), Circa 1987. They let me have it after we | |
plugged it up and determined that it doesn't even idle properly; all of | |
the status LEDs light up, but it should only have the power LED lit if | |
all is well, perhaps the alert LED should blink if there's no paper too. | |
When I got home I popped it open and determined that it contains an NEC | |
D7810HCW CPU with a 14.7 MHz clock crystal. I looked up the datasheet | |
for the CPU and determined that it is normally clocked at 12 MHz, and | |
contains 256 bytes [sic] of RAM and 4K of ROM. (note: ROM and RAM are | |
both externally expandable, but Tandy definitely is using only the base | |
amount of RAM on this printer) | |
The CPU is a nominally 5 volt CPU, the onboard RAM fails to function if | |
it dips down to 3.2 volts. | |
Armed with that little bit of information, I started probing a few spots | |
on the mainboard that conveniently had voltage labels and determined | |
the +5 VDC rail of the PSU is only putting out around 2 VDC. 😱 | |
No wonder it doesn't work! | |
I found a SAMS Photofact which shows that the other rails on the PSU are | |
+24, +12 and -12; not terribly unusual for a printer of this vintage. | |
But there are not many quadruple output power supplies these days either | |
that are not expensive. I couldn't find a specification for the number | |
of amps each rail is supposed to output either, but the primary side of | |
the existing power supply surely doesn't draw more than 2 amps or about | |
20 watts according to the sticker on the bottom of the printer and the | |
manual I have been able to find online. I have decided to go with a | |
Mean-Well RQ-65D as it matches the input amperage and has the required | |
voltages on its output rails. | |
For input, the printer has a centronics port which I will not be using, | |
and an RS-232C port with a 4-pin DIN connector of some type, it is using | |
only the common ground, transmitted data, and data terminal ready parts | |
of RS-232. From what I can tell the port expects the 8-N-2 configuration | |
at a baud rate of 600, 1200, or 2400. | |
Will update again once I have the replacement power supply... | |
Owner's manual | |
CPU datasheet | |
SAMS Computerfacts Technical Service Data | |
Potential PSU datasheet | |
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I have a DMP 107 next to me now. Connected with a DIY PC-compatible LPT | |
cable it even works in modern Linux, inc gfx ~freet | |
Posted Sat Aug 5 00:58:53 UTC 2023 by 1.152.108.92 | |
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