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PDP8/A (front panels wanted)

Roland Huisman

Roland Huisman

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Joined
Mar 24, 2011
Messages
1,465
Location
The Netherlands
I've got this PDP8/A box with four boards. (I still have to pick it up) It has a CPU board, mem board, MIO board and another from which I don't know what is it yet. (probably something with boot ROMs)

8A.jpg20220909_102636.jpg20220909_102722.jpg20220909_102745.jpg20220909_102823.jpg


BUT... I'm missing both of the front panels... Can someone help me to get these panels? That would speed up the restoration story here ;)

Thanks in advance!
Regards, Roland
 
Hi Dave,

I think my question was not as clear as I thought... I was assuming the dec readers knew what an 8/A looks like... I'm looking for the boot panel and the programmers console. Both are missing. As far as I know Rod only made a few of the colourfull plastic fronts without electronics.

Regards, Roland
87338.jpeg


87339.jpeg
 
Nice looking 8/a. Looks like you have a semiconductor memory (32k maybe) in photo 2, an M8316 option 1 board in photo 3, an M8317 option 2 in photo 4 and an M8315 KK8A CPU in photo 5.

The option 1 board has the console serial port, A 12 bit parallel input port, a 12 bit parallel output port, the front panel interface and the Real time clock.

The option 2 board is the combination of the M837, M847, and M848 boards.

A lot of these machines were shipped without the programmers console. They only had the limited front panel which is the one in your second photo above. One of those switches toggles the boot rom on the Option 2 board similar to the init switch on the 8/e front panel.

I have several of the hex semiconductor memory boards and none of them will pass diagnostics. The DRAMS seem to not have survived as well the passage of time. I have several 16k core board sets and all of them work great.

The recommended placement for the cards is M8315 CPU in the top slot. The M8316 and M8317 can go in either slot 2 or 3 and the memory goes in slots 4-8 which are all 5 connector slots. The 5th connector has the extra lines to select which of the 32k boards are selected when it was equipped with up to 128k. There was also a 128k memory board but the one I have does nothing except get hot.

I hope you find a front panel. I have one that works and one that needs fixing and three machines.
 
Roland,

I was on holiday and posted with my phone - so I didn't have the luxury of looking up the panel. But now I am back, and you have posted a picture, I see what you are saying!

Ignore my post :)!

Dave
 
I believe the 8/a programmer's console shares a metal casting with the 11/34a programmer's console.
If you get really hard-up, I have a fire-damaged 11/34a panel that with some scraping, scrubbing (or sandblasting) and paint, would at least give you something to mount to the chassis and mount some electronics to. I wouldn't expect to salvage anything else off it. Yours for the (not insubstantial) cost of shipping. PM me if you want it.
 
Roland Huisman said:
I'm missing both of the front panels... Can someone help me to get these panels? That would speed up the restoration story here
Click to expand...
board1.jpg

Just making sure you're aware of the KC8A Programmer's Panel documented at VRS's site. Vince can probably drop the URL to the Eagle CAD files if you don't want to wait for a DEC one to come available.
 
Teletech said:
I believe the 8/a programmer's console shares a metal casting with the 11/34a programmer's console. If you get really hard-up, I have a fire-damaged 11/34a panel that with some scraping, scrubbing (or sandblasting) and paint, would at least give you something to mount to the chassis and mount some electronics to. I wouldn't expect to salvage anything else off it. Yours for the (not insubstantial) cost of shipping. PM me if you want it.
Click to expand...

Thanks, Jos has also an 11/34 panel for me which is coming to me. But it seems they are a bit different. The 11/34 is open for air and I'm not sure if the opening from the 11/34 is the same as the 8/A. Is the front from the 8/A also build in the same way as the one from an 11/34?
IMG_20220516_113220.jpg

ftcnet said:
Just making sure you're aware of the KC8A Programmer's Panel documented at VRS's site. Vince can probably drop the URL to the Eagle CAD files if you don't want to wait for a DEC one to come available.
Click to expand...
Thanks, that would be fun but it seems that Vince did not make a clone which is mechanically compatible with the original front. And reading his story it seems there are some bugs in the PCB's as well... So in this case I prefer an original front for the machine. I know that this can take a while...

Regards, Roland
 
FWIW DEC has two different part numbers for the bezels:
(1) E-MD-7415599-0-0 for the 11/04 or 11/34 KY11-LA or KY11-LB
(2) E-MD-7412349-3-0 for the PDP-8A KC8-A
so their are likely differences in mounting holes, key dimensions, as well as the obvious ventilation slot differences.
 
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I *might* have the boot console.
I do not have the programmer's console, and doubt (pretty sure) that the metal 11/34 programmer's console is different.
Maybe the keypad is identical, but the LEDs left of the keypad is very different (but that is obvious :) ).
 
IMG_5315.JPG


This foto was made during fixing an 8/a. From the positions of the screw holes I beg you cannot change the front. Also the front plastic frame with keyholes is glued to the front.
Volker
 
gnupublic said:
This foto was made during fixing an 8/a. From the positions of the screw holes I beg you cannot change the front. Also the front plastic frame with keyholes is glued to the front.
Volker
Click to expand...
Thanks! You confirmed what I remembered to have seen before. Totally different from the 11/34.

@Henk, I've sent you an email. Would be great if the panel you have is indeed the same as for the 8/A.
 
Roland Huisman said:
Thanks, that would be fun but it seems that Vince did not make a clone which is mechanically compatible with the original front. And reading his story it seems there are some bugs in the PCB's as well... So in this case I prefer an original front for the machine. I know that this can take a while...
Click to expand...
I didn't have a source for the keypad, so I just used bog-standard tactile switches with the little square plastic buttons that go with them.

I think the functional issues have been mostly cleaned up. It occurs to me that I've got an 8/A which I expect to be working with soon, so I'll have a chance to renew my expertise wrt. getting one of my clone panels working.

Vince
 
Last weekend I've picked up the PDP8/A. It seems to be some sort of OEM machine, used in an special application. There is no normal mains cord, but it is made to connect into some sort of bigger machine. The Blue, Brown and Yellow/Green wires are for the mains voltage supply.


PDP8A 01.jpgPDP8A 02.jpgPDP8A 03.jpg

The DIP-16 cable connector, inside the machine to connect the limited boot panel, has a jumper socket in it. And at the rear of the backplane are some modifications. So I think this machine will boot automatically or the boot is triggered through the other external cable.

PDP8A 04.jpgPDP8A 05.jpg

I've visited Henk and he magically has two of these limited boot panels. But the mechanics and electronics are different as well as the text on the front.

The left panel has a battery charging function and the right just has DC-OK. I think the battery version should be suitable for my machine since it has RAM instead of core memory... But I'm not entirely sure.

PDP8A 07.jpg PDP8A 08.jpg

PDP8A 10.jpg PDP8A 11.jpg

Here you can see the back of the panels. The top one seems to be made for a big cabinet and the lower one fits on my small case.

PDP8A 09.jpg

My machine is a 8A400-BR (On a label is written: Product variation: Model changed. From: 8A400-AB to 8A400-BR)

Does anyone know where I can find the documentation which describes these modifications? I found some 8A500 documentation... But I'm not sure about the differences between these two.

The boards inside the machine are,
8315 - CPU
8317 - ext mem and bootloader
8316 - multi function board
8417 - 32KW memory

There are two ROM's on the bootloader board, but the labels are gone. I have to read them, I wonder what bootstraps are inside them. Maybe these were application specific too.

Still searching for an octal frontpanel for this machine.

Regards, Roland
 
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I've never seen the panel with the Battery Charging LED although I have read about them. The battery is supposed to keep the memory alive for a short period of time. I remember reading 30 seconds or so. I've not seen one of those machines with batteries which would have been NiCd types and at this point would have leaked out their Sodium Hydroxide and done all the damage they were ever going to do. The semiconductor memory boards seem to work fine in a regular machine. At this point there is no reason to replace the battery, an external UPS is a better solution all around if you want to keep it running through a black or brownout. If you want it to look like the battery is there just 3D print a battery lookalike.

From memory the version of the ROM is on the factory ink labeling. I don't remember any paper labels that could fall off. It could also be labeled on the bottom of the chip if you haven't looked there. All that stuff is buried away right now or I would just go look at it. There are several devices supported in each of the different ROMs and you select which one you want with some DIP switches. I have some supposedly unburned ROM's that Warren had bought off of eBay a long time ago. I don't know what his plan was for them.

If you don't have a reader for those ROMS the quick way to read the ROMS is to zip memory to zero and then toggle the boot with no I/O cards installed. Halt the CPU and read memory to see what got loaded. Then zip memory to all one's and toggle the boot. This will find stuff that got set to all zeros. This will get you 99.9% of the way there.

I can't think of anything that describes the changes. There is a difference between the North American and European models and that is the 60hz vs 50 hz transformer. A ferro resonant arrangement would be sensitive enough for the frequency to be an issue.

A neat little machine!
 
DougIngraham said:
Let us know if Santa grants your wish.
Click to expand...
Well, it is Roland, so it could happen :). Even if it was initially non-working, I bet Roland would have it refurbished and looking.working great in short order.

As mentioned upthread, I do also have some PCBs for a clone of the programmer's panel.

Vince
 
The school year is coming to an end and most of our students have holiday now. So I have some time for myself again. Changing to a new job on another school took a bit more spare time then I expected to be honest. :oops: But no regrets, I really like it :biggrin:

So in a few weeks I have holiday myself and I would love to make some progress on the PDP8/A. But I'm still in need of an octal front panel. Does anyone have one for sale or swap?

Regards, Roland
 
Some weeks ago I was allowed to save a PDP-8/A from a basement of a house that was sold before. I brought the small rack to Oldenburger Computer Museum (OCM) in the north of germany. This litte beauty is a very small configuration, just the CPU with the limited panel , RX-01 and VT-52 terminal and printer (Logabax), nothing else. So the missing switchregister might be quite normal for small configurations?
This just in case you don't find one....

Download (4).jpg

Have fun,
Volker
 
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