Building a PDP-8 straight 8!

[rorypoole]

I am working on building a PDP-8 straight 8, at the moment I am doing research on the pdp8 and buying what parts I can, I will build the flip chips and other parts I cant get. so far I have 1X R111 5X R107 5X R202 flip chips a book introduction to programing 1972 for the pdp8, 4x 6250 bpi reel to reel tapes, and a box of 12 type M flip chips, and a lot of boxes of raw ferrite cores for the core memory.
I have some more parts on the way

any help welcome

 

[bobvines]

Rory,

Where did you get the boxes of raw ferrite cores? It seems like they would come in handy if major surgery had to be done to repair an existing core memory.


Thanks,

Bob

 

[rorypoole]

Rory,

Where did you get the boxes of raw ferrite cores? It seems like they would come in handy if major surgery had to be done to repair an existing core memory.

Thanks,

Bob

I got them from a guy on ebay, search for raw core memory and have ebay set to worldwide, he sells two sizes of cores and different amounts of them, I dont know if they would have the same properties as the cores in a core memory plane you wanted to fix, core memory is hard to get working!!
I got

 

[rorypoole]

parts I now have for pdp8 build
I have now got 12 sheets of Paxolin pcb copper clad boards, and they are 17 X 5 inches so can make 72 filp chips! and I have more copper clad Paxolin in storage! I also got some more flip chips.
I now have 1X R111, 5X R203, 5X R202, 5X R107, and for trading 4X M103, 1X M111, 1X M121, 2X M149, 1X M206, 1X M248, 1X M510, 1X M622,

 

[rorypoole]

I also go a tin of about 200 acy 19 or cv 7437 pnp germanium transistors to use, I have also got 2 non working 300w dec h704d power supply's to power my FPP-12A Floating Point Unit,
I also have got some USSR Soviet Ferrite Core Memory, to help me with my core memory winding

 

[rorypoole]

close ups of the 200 ~ acy 19 or cv 7437 pnp germanium transistors to use, and the USSR Soviet Ferrite Core Memory to help me with my core memory winding, I have a lot of vintage and modem electronics parts not shown, for the project

 

[rorypoole]

I have picked up my first RL02 and RL02K-dc disk pack, and 3 used a 1 unused pdp 12 packplans, that enough for 50% of the basic straight 8! also a dec 861b power control unit! from the 1980's its rated for up to 16A and has 240v usa sockets on it? the RL02 also has the same type of 240v us plug on it? it looks like I will have to order some 240V 15A NEMA 6-15 plugs and sockets!!

so it seem that dec used only us plugs and sockets, even on there export stuff

also in the post I got 50 old metal caned 2n2222A transistors, and 160 vintage ME6002 (2n2222A) transistors and about 100 BF159 transistors, the ME6002 and BF159 have gold plated legs why gold plate the legs? I also got 2 small sets of 1n34 germanium diodes I already have a load of other parts.

 

[rorypoole]

the Nova 3 dose something cleaver "Each bulb has a 1k pull-up resistor to allow a small current to flow through it during its "off" state to keep the filament warm. This prevents the bulb suffering from thermal shock when it fully switches on therefore increasing its life"
http://www.chookfest.net/nova3/ledmod.html

and it looks like the Novea 3 uses 28v 0.04a lamps same as the pdp8,
http://www.foxdata.com/blog/?tag=nova-312

I dont yet know what the straight 8 supply it ran the lamps from but I think there is only the +10v -15v and a 20v? supply for core memory, as the 15v line is very low output, I think they must be running off the +10v. if the supply was 24v the lamps would get 0.015 amps when off! or 0.0075 amps~ on a 12v supply

 

[NeXT]

Let me put it to you like this:
The original straight-8 PSU was very, very big.

 

[rorypoole]

thanks for the pic, I will have to read up more on the power supply outputs! but I will have to design my own liner power supply

 

[rorypoole]

RL02 drive and used pdp12 packplane

 

[rorypoole]

any one know the max usable frequency of a 1N4007 rectifier diode?

 

[cruff]

any one know the max usable frequency of a 1N4007 rectifier diode?

Most datasheets for the 1N400x series I found with a quick Google search did not mention any frequency (or time) related parameters. I found this interesting discussion of the forward and reverse discovery times for various diodes: http://www.cliftonlaboratories.com/diode_turn-on_time.htm, which mentions the use of a 1N4007 as a RF switching diode in amateur radio equipment, and shows a graph of the forward recovery time for a 1N4007 as <1μs, which would be >1 MHz.

 

[rorypoole]

Thanks Cruff, so it looks like I can only use them for the on board flip chip shunt regulator and relay snub, and maybe psu in the pdp8

 

[rorypoole]

Let me put it to you like this:
The original straight-8 PSU was very, very big.

where did you get the pic?

 

[NeXT]

pdp8.net has a section on the rebuilding of the PSU so it won't explode the moment you power it up.

I don't want to rip on you and you're plan is nice but you REALLY need to do some research before you start amassing hardware, some of which you will not even be able to use at all. Build up a complete list of components you need to buy or have built.
Find a recycled laser printer and write off a weekend and look through bitsavers and google. Your straight-8 project is not going to be as easy as ADD PSU, ADD BACKPLANE, ADD CARDS AND INSTANT COMPUTER. Before you start building disk interfaces or expanding memory or adding terminals get a base system that will reliably input code from the front pane, THEN you can look into your RL02 interface or core memory or tape drives or terminals or floating point option.
You still have PLENTY of space to paint yourself into a corner with by purchasing random DEC and computer junk and end up passing the current price points for other PDP-8 systems to the point you are paying MORE to build your system than it would be to say purchase an 8/e off ebay.

 

[rorypoole]

I am planing the pdp8 build even though it looks like chaos, I have a spreadsheet of needed flip chips, and I worked out its cheaper to buy the 1960 flip chips but only just, and I cant make a master list of all electronic components needed as most of the old 1960 components used are too expensive or you cant get them, so I am buying small samples of the modern components and will test them on a breadboard, the first card I will do is the R111, as its a simple flip chip and my first part I got for my pdp8 build, I found the same type of transistor used in a later version of the R111 on ebay mislabeled so I got 500 very cheap, any components I find unsuitable I can sell or keep for another project, and some parts like the two dead switched mode power supply's and the RL02 drives and disk packs and magnetic tapes and drives, I am getting now and storing for later when I can use them when the pdp8 is working.

I have started a spreadsheet of all the components I have for the project with full teck data, and when I get back in 2 months I will breadboard the R111 flip chip, and test different component I think will work, I will compere it with my real R111.
I had looked at the straight 8 power supply, but as I cant get the special constant voltage transformers I stopped reading up on it, I can build a liner power supply for it later when I need to, for now all I need to do is run two flip chips.
some of the parts I have got like the non DEC 1960 computer boards I got for fun and the USSR core memory I will probable never be able to use but it looks cool and can help my make my own core memory.

I have also just got a stack of DEC book stuffed with needed info, like how to decode the backplane wiring plan! and wire wrapping the DEC way. I should have researched the RL02 drive better before I moved it, but it had been moved already by moving guys that did not have a clue what it was, I may get lucky and its fine, I will see when I get back?

Vince recommended http://alltransistors.com/ and its great and saving me a lot of time!
the two dead switched mode power supply's are for the FPP-12A as it need 5v and the pdp8 used 10v+ and 15v- and another supply for the core memory.

I have been printing some of the old data sheets in my maths classes! as its free, but I will have to get my old epson printer out of storage, I got it for £0.01 to try making PCB's with

in the end I will probably spent more than buying a pdp-8/e but I want a straight 8 and buy building it I will have some fun and learn a great deal on how it works, and how to fix it, lol

and I have decided to build a semiconductor core memory replacement, and use it till I have the pdp8 fully working, them I will build the core memory and fit it!

 

[rorypoole]

I have got a working Silicon Graphics SGI Octane UNIX workstation for £27 plus £14 for the bus and train to pick it up, it has IP30-based MIPS R10000, dual 250Mhz CPU board, 1Gb RAM and Sun 20" CRT monitor, both are extremely heavy! I also got a SGI Indy with 16inch Silicon Graphics monitor web cam keyboard and mouse for free!!, it is all very dusty, I have no idea what I will do with the Indy?
I got the Silicon Graphics Octane to learn UNIX and as a CAD workstation, and will be connected to the pdp8, I could use a modem computer but the Octane looks so cool!

 

[woodchips]

This doesn't seem to be the thread I was looking for, they seem to drop off the edge of the world after a month or so.

Anyway, Quarndon Electronics, quarndon.co.uk, in the UK have an interesting collection of ancient 74 series chips, and-or-invert gates, look ahead carry, ALUs etc in a range of technologies. I have bought a few devices at very reasonable prices. If after anything give them an email.

They even have some new 8" floppy discs!

 

[rorypoole]

thanks for the info on Quarndon Electronics, I have been away volunteering and have only recently got back home, I will still be working on the pdp8 build and now have 250 bulbs for the pdp front panel!