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A new PDP-8 in the collection!

pbirkel@gmail.com said:
Thank you for the explanation. What was the benefit to using this configuration with both front/control panels in play?
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Just to test parts, one by one and verify them.

DougIngraham said:
I always wondered if you could plug an E front panel into an A chassis with an A front panel connected. It looks like it does work! What I am questioning is why the displays are not showing the same thing. The E panel shows the MD as 6232 and the A shows it as 232. What am I missing?
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Just as gnupublic wrote, thge exposure time is to shot to catch all numbers.
 
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Well, I have now added a second serial port into this machine. I would like to boot OS/8 with serialdisk. This would make it much easier to run maindecs. But for this I need 8K of memory so I added a MS8 M8311-YD (4K) PDP-8A MOS memory module configured for field 1, but it didn't work. I tried two different boards that I know I have fixed and tested before, but in a 8A with KK8A. Are those know to work in a 8/E? I will test them in my 8A, but I just made space on the lab bench by lifting it down and put it on the floor. Back it goes.

I do have an extended memory control board (M837) in the machine, tested good.

Maybe it's just time to build another omni32K memory board. I have an empty PCB, but then I found Vince new version that includes Rolands boot loader. So many choices.

And I must admitt, my BC01 serial card, yea, that didn't fit...
IMG_2780.JPG
 
I don't remember exactly what the issue with the M8311 is when used with the KK8E cpu board set but I think you are correct and it won't work. The KK8A is a 1.5 us memory cycle and the KK8E is normally a 1.2 us cycle for the fast cycle. You can jumper it to do 1.4 us for all cycles but I am not sure that will be slow enough. The KK8A CPU drives many of the bus signals with tri-state outputs instead of open collector. I have several of the hex width dynamic boards for the A, none of which are without errors. I have a note that these won't work with the early KK8E cpu's because the cpu does not support the memory stall signal. Presumably this might be required during DRAM refresh cycles. The M8311 might also need the memory stall signal to work correctly. I don't have any of the M8311 boards although I have been looking for one for a while now.

From the 8's standpoint you only need three wires in your serial cable. The 8 with M865, M8650, or M8655 as the console don't look at any of the extra RS-232 signals but they do generate voltages so the devices they connect to will wake up.

You could also use my CSD (Console Serial Disk) program and then you only need one serial card. You can find it on GitHub. It uses a different boot than Kyle's Serial disk but it is only 8 instructions long so not to onerous to use. You still need at least 8k though.
 
Next question, where can I find a matching connector? This sits on the power supply, and I need to build a power cable harness to the second backplane.
IMG_2781.JPG
 
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:)
 
anders_bzn said:
Wow! Thanks!
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Quick caution - you probably aren't going to build enough of these to make buying even the least expensive crimper for the pins worthwhile. In addition to closing the "u" where the stripped wire goes with needle-nose pliers, you should solder the wire to the pin or you'll eventually develop high resistance which will be a Bad Thing.
 
Terri Kennedy said:
Quick caution - you probably aren't going to build enough of these to make buying even the least expensive crimper for the pins worthwhile. In addition to closing the "u" where the stripped wire goes with needle-nose pliers, you should solder the wire to the pin or you'll eventually develop high resistance which will be a Bad Thing.
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I would buy a cheap but half decent manual crimper. It lasts a lifetime and pays for itself many times over.
 
I have a decent crimper that I think should work for those pins. I will order 100 pins, so I can waste some so I can evalute...

Which wire gauge sould be used? I guess on something between 14-16.
 
thunter0512 said:
I would buy a cheap but half decent manual crimper. It lasts a lifetime and pays for itself many times over.
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Have you looked at the price of "cheap" Molex brand crimpers?😱

Many of the clones either only work with the same clone manufacturer's pins or pretty much not at all.
 
Terri Kennedy said:
Have you looked at the price of "cheap" Molex brand crimpers?😱

Many of the clones either only work with the same clone manufacturer's pins or pretty much not at all.
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Unless your work in safety critical aerospace or medical devices industries or do a lot of crimping you don't need the manufacturer's crimping tools.
For the hobbyist the generic crimping tools are absolutely sufficient.
They may require a bit practice, but if properly used make perfect crimps which are infinitely better than trying to do it with pliers and/or soldering.

One of many examples is: https://www.amazon.com/ENGINEER-AWG32-AWG20-Connectors-Oil-Resistant-PA-09/dp/B002AVVO7K

That specific one is US$33. This is a quality Japanese tool.
There are many others, some under US$20.

To learn how to use a crimping tool properly watch some YouTube videos.
Google something like "youtube how to use a generic crimping tool for molex connectors".

One of many examples is:
 
While I'm waiting for cabels to the power cable assemby I built replacements for the M935. I used a pair of BC08H cables in my version. I kept them really short.
IMG_2794.JPG
 
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