Building a PDP-8 straight 8!

[rorypoole]

some great pics of a pdp8, useful info on core memory boards in the pics, I need to find info on the 51 and 52 red transformers some time
http://www.computerhistory.org/revolution/minicomputers/11/331

 

[rorypoole]

I am going to go to the london hackspace and have a go at making a R111 flip chip

 

[rorypoole]

some others are working on building a pdp8, but this one is being built in minecraft!
www.minecraftforum.net/topic/1061377-redpower-pdp-8-project/

 

[amadama]

some others are working on building a pdp8, but this one is being built in minecraft!
www.minecraftforum.net/topic/1061377-redpower-pdp-8-project/

Pretty impressive. It's a shame he has stopped working on it for now.
Best of luck to you on your PDP-8 project. It's a huge undertaking and I wish you great success.
Looking forward to following your project.

 

[rorypoole]

the London Hack space is great, but the etching tanks need plumbing in

 

[rorypoole]

I have started unwinding the old wire wrap off the pdp12 cut backplane sections, this could take some time! I have not stopped working on the pdp8 project!

 

[rorypoole]

www.pdp8online.com/straight8/functional_restore.shtml
>The backplanes contain 230 cards, approximately 10,148 diodes, 1409 transistors, 5615 resistors, and 1674 capacitors.

and apparently DEC had a lot of ECO / engineering change orders, so I will also have to look them up!

 

[Marty]

Hi All;
Rory, I want Thank You for this Link, I have looked at and Read with interest What all He did to get His machine running.. And I have learned some thing I didn't know.. Looking at This site makes me Almost want an Early 8, But I have enough problems with my /40.. Granted, possibly learning Early Transistor - diode logic, might make my TroubleShooting of later TTL logic somewhat easier..
THANK YOU marty

 

[rorypoole]

margin switches

margin switches

I found some Stackpole switches that look like the margin switches in the straight 8 but are double pole, I got a pack of 30 in case! they are rated at 0.5 amps at 125v. I could wire the poles together to make it more reliable, but how close are they to the original straight 8 margin switches? and is the 0.5 amps enough?

maybe not, if I get the -15 line and divide the max 15 amp output by 12 sets of margin switches I get 1.25 amps, so need 2 amp dc switched min


www.ebay.com/itm/STACKPOLE-SLIDE-SW...223?pt=LH_DefaultDomain_0&hash=item257ddf7fe7

David Gesswein pdp8
http://www.pdp8.net/straight8/backplane_restore.shtml
http://www.pdp8.net/straight8/pics_backplane/moving_contact.shtml

also I have found some switched that could be possible to be used for the front panel? but with new pdp8 handles!
http://www.ebay.co.uk/itm/Stackpole...464?pt=LH_DefaultDomain_0&hash=item2a2f5f0f78
http://www.ebay.co.uk/itm/STACKPOLE...495?pt=LH_DefaultDomain_0&hash=item3c8f3b6e3f

David Gesswein straight 8 switches
http://www.pdp8.net/straight8/pics_front_panel/P1030010.shtml?small
http://www.pdp8.net/straight8/pics_front_panel/broken_handles.shtml

anyone have any info on the 4jx1c741 transistor used in the straight 8 front panel? or a circuit diagram? all I can find is they are probably germanium and pnp?
http://www.pdp8.net/straight8/pics_f...46.shtml?large

 

[MerrickD]

Same as 2N527

Details: http://alltransistors.com/transistor.php?transistor=4691

 

[rorypoole]

I found some Stackpole switches that look like the margin switches in the straight 8 but are double pole, I got a pack of 30 in case! they are rated at 0.5 amps at 125v. I could wire the poles together to make it more reliable, but how close are they to the original straight 8 margin switches? and is the 0.5 amps enough?

maybe not, if I get the -15 line and divide the max 15 amp output by 12 sets of margin switches I get 1.25 amps, so need 2 amp dc switched min

View attachment 17200View attachment 17199View attachment 17198View attachment 17197View attachment 17201
www.ebay.com/itm/STACKPOLE-SLIDE-SW...223?pt=LH_DefaultDomain_0&hash=item257ddf7fe7

David Gesswein pdp8
http://www.pdp8.net/straight8/backplane_restore.shtml
http://www.pdp8.net/straight8/pics_backplane/moving_contact.shtml

also I have found some switched that could be possible to be used for the front panel? but with new pdp8 handles!
http://www.ebay.co.uk/itm/Stackpole...464?pt=LH_DefaultDomain_0&hash=item2a2f5f0f78
http://www.ebay.co.uk/itm/STACKPOLE...495?pt=LH_DefaultDomain_0&hash=item3c8f3b6e3f

David Gesswein straight 8 switches
http://www.pdp8.net/straight8/pics_front_panel/P1030010.shtml?small
http://www.pdp8.net/straight8/pics_front_panel/broken_handles.shtml

The margin supply is 2 amps max at 10 to 15v, so the switch has a max load of 2 amps at 10 to 15v dc, but they would not be used often, and I have thought about shorting the poles together, doubling the current capacity, but that only gets me to 1 amp? but I think most of the time the switch will be used with the power is off, and I can use a snubber (a capacitor and resistor wired in series in parallel with the contact) and as the ac rating is 3 amps per contact, and I am using it about 8 times lower voltage, so that should help limit the arcing, I could it be ok?

 

[rorypoole]

In the next week or two I am going to build a few of the pdp8 logic circuits on stripboard to test the transistors that it was designed with and my selection of possible subs to see how it effects the circuit, also I am going to try the lamp out I got for the straight 8.

 

[rorypoole]

I am still unwrapping the used pdp backplane parts, this is going to take me some time! I am also studying flip chips, I think I will try making a R201

 

[rorypoole]

Today a load of DEC parts arrived, I have wire wrap prototype flip chips that will be useful when the pdp8 is working to build custom controllers with, I also got 22 DEC handles! with rivets.

 

[rorypoole]

wide flip chip wire wraping boards, H3006 8-line EIA panel, and 26 flip chip spacers, what are flip chip spacers used for?

 

[rorypoole]

wirewrap tool for the H808 connecter block, 32! flip chip card extenders, 14X H8080 DEC socket 2 slot, 2X H808 4 slot dec socket (like the straight 8 used)

 

[rorypoole]

H808 and H8030 DEC sockets, see how much wider the H808 pins are!

 

[rorypoole]

you can see the different size on pins on the DEC sockets

 

[rorypoole]

more wire wrap boards, and a bag of the needed screws for the connector block!!

 

[Lou - N2MIY]

Are the card spacers are meant to fit between the handles? The handles themselves act as spacers, but don't clamp the cards together. Will these spacers will clamp the cards together?

Lou