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PDP-11/34 CPU PROMS

P

Panelman

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Joined
Apr 21, 2016
Messages
39
Hi
Jerry Walker and I have an 11/34 under restoration.
We have run into a bit of a problem.
On the M8266 CPU control board a defective 7404 (E111) has killed a bunch of the PROMs holding the microcode.
Does anybody have or can get images of the PROMs on this board so replacement devices an be programmed.
Rod
 
Did you see the files on bitsavers? Don't know how useful these are for you.

I checked the M8266 schematic, but I don't understand how a defective 7404 could
damage the ROMs. The 7404 has only a 5V supply. So the outputs can only be between 0 and 5V.
Even with a completely fried 7404 the output will not exceed the 5V. So it will not kill the ROMs.
So I'm curious what really happened.
 
Jerry's video is up with a little more detail. He indicates that an input to the 7404 is shorted to 5V and believes that one of the open collector outputs was damaged trying to pull that line to ground. I've never seen that particular failure on an input but I am sure it could happen.
 
I thought the 11/34 CPU ROMs had been archived online somewhere but perhaps I'm muddling it up with something else like the M9301..?
If nothing turns up I'm happy to lend you a spare M8266, assuming one of you has the ability to dump them.
 
TJ_Mossman said:
I thought the 11/34 CPU ROMs had been archived online somewhere but perhaps I'm muddling it up with something else like the M9301..?
If nothing turns up I'm happy to lend you a spare M8266, assuming one of you has the ability to dump them.
Click to expand...
Yes please .. Jerry is in Hereford not far from you.
 
I've sent Jerry an email. I have a couple complete boardsets for the 34a as well as memory, serial, and disk I/O (RX01, RL02, RK05) too if they're of any help.
 
Sorry to dig this up. I am also restoring a PDP-11/34, and I strongly suspect that one of the CPU ROM is faulty. Has there been any progress regarding the dumps? I don't think Jerry made any mention of it since his video.
 
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