PC04 resurrection

I recently got a DEC PC04. I initially thought it was a PC05. But it is "only" a PC04. Exactly what I've been looking for. I already had the PC8E controller waiting for a suitable reader/punch.

These few pictures try to show what can be done by simply cleaning things.


One level up

1. Untouched

1024x768    Full size		What's that......
1024x768    Full size		Good used condition
1024x768    Full size		Will this ever work again? Yes, I thougt .-)
1024x768    Full size		Chad everywhere.... I hate that stuff!
1024x768    Full size		Everything full of chad - ecept the chad box which I emptied when I picked up the unit.
1024x768    Full size		Fuses are obviously stolen.
1024x768    Full size		"moving" parts
1024x768    Full size		It was nearly impossible to turn the knob or the punch's main shaft.
1024x768    Full size		img_0889.jpg
1024x768    Full size		There's something missing. I have never seen this kind of rod coming out a DEC backplane.
1024x768    Full size		The punch's immovable guts
1024x768    Full size		Dirty switches
1024x768    Full size		The reader
1024x768    Full size		img_0903.jpg
1024x768    Full size		img_0907.jpg
1024x768    Full size		There's some slight distortion at the corner
1024x768    Full size		img_0917.jpg
1024x768    Full size		img_0918.jpg
1024x768    Full size		img_0923.jpg

2. Cleaning

1024x768    Full size		The front comes off
1024x768    Full size		The reader lamp - it is intact.
1024x768    Full size		Chad is everywhere!
1024x768    Full size		Front bezel before washing
1024x768    Full size		And after. It has lost most of its gloss. I think this is caused by removing grease from the aged plastic surface. A little amount of "spit and shine" with a little bit of oil and a wet cloth fixed the problem.
1024x768    Full size		Cleaning has already begun!
1024x768    Full size		img_0950.jpg
1024x768    Full size		First improvement: The chad is mostly gone!
1024x768    Full size		The punch after a one hour treatment with a solvent and oil. Some of the plungers were nearly immovable in their holes. It took a lot of force and patience to get them sliding easily again. The rest of the mechanics was easier to make moving. (I forgot to take pictures of the unit partially disassembled - Must have been too concentrated)
1024x768    Full size		Getting "on line" with the PDP-8/e. The reader does simply nothing without a powered PC8E controller. The reader is driven by a stepper motor. This motor has four windings which must be controlled by the PC8E. The PC04 does not have any means to sequence the reader motor. So a "local" feed (key on the PC04) commands the PC8E to advance the tape.
1024x768    Full size		img_0969.jpg
1024x768    Full size		img_0970.jpg
1024x768    Full size		When trying out the reader (punch worked fine), I had the problem that the reader always skipped one character. After looking at the schematics, I suspected three 7400 to be possibly bad (already marked them). And then I saw it: My PC8E was heavily patched. I don't know why. Could imagine that it was to use a more capable reader which doesn't need the stepper motor control.
1024x768    Full size		There had been a bridge inserted (already opened by me) and one of the signals cut (picture above) so that the data strobe would be generated on the second of two steps.
1024x768    Full size		These wires are patches, too. They look very factory installed. I think My PC8E is some more modern version which has been made compatible to something else than a PC04. I had to remove all those wires and close the cut tracks. That resulted in the wiring as shown in the schematics which I found around the web (bitsavers). Et voilà: It works fine now!
1024x768    Full size		Already a bit cleaner!
1024x768    Full size		img_0998.jpg
1024x768    Full size		img_0999.jpg
1024x768    Full size		Clean cards
1024x768    Full size		Easily movable mechanics
1024x768    Full size		No chad around the box
1024x768    Full size		Most work is done

3. Ready to rock!

1024x768    Full size		Everything except the cables is reassembled, the last reachable corner has been cleaned.
1024x768    Full size		img_1008.jpg
1024x768    Full size		img_1009.jpg
1024x768    Full size		img_1010.jpg
1024x768    Full size		img_1011.jpg
1024x768    Full size		It just makes another impression now....
1024x768    Full size		img_1020.jpg
1024x768    Full size		img_1022.jpg
1024x768    Full size		Clean punch
1024x768    Full size		The front. - As half-glossy as before. Looks nice.
1024x768    Full size		img_1027.jpg
1024x768    Full size		Clean keys
1024x768    Full size		And a cleaner backplane. That's it.