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Powertran Cortex

Jim Hearne said:
There have been more bare boards listed on ebay
http://www.ebay.co.uk/itm/250879547778
Click to expand...

And a third set of boards has now been listed.
I got the second set - for a price cheaper than the first!

Jim, on the Cortex 2 parts you got, are there any markings on the key switches that indicate who they're manufactured by and what the part number is? I'd also be interested in who you've bought chips from so far - by private message if appropriate.
 
Jim Hearne said:
Some pictures of what i've just bought from the same guy selling the PCB's on Ebay.
Apart from a few missing TTL and RAM chips it's a complete basic Cortex 2 kit.
Who'd have thought a unbuilt kit would turn up after almost 30 years !
View attachment 6512View attachment 6513View attachment 6514
Click to expand...

Did you get any assembly instructions with the kit, Jim? The PSU PCBs he's sending out appear to be for the Cortex 2 and have been redesigned from the one in the ETI article, but the PCB doesn't have any component markings on it. It might be bigger to accomodate a heatsink for the two transistors that were previously bolted to the metal case?
 
Sorry Stuart,
I didn't spot there had been more replies to this thread till just now.

The 3rd set of boards are already more as i put a bid on them as a spare set :-(

Most of the chips came from Ebay, the TMS9911 cost the most, probably a bit too much but as i'd got the rest i didn't want to wait around to see if one came up cheaper.
The TMX9909 i found through google on a web site from a guy in the UK with a list of chips for sale but they were the only 2 that the seller had i believe.
There was another web site (Mikes electric site i think) with some TMS9911's on but when i asked about them the seller couldn't find them, shame as they were a lot cheaper.
The TMS9902 came from China, they came as a pair but one was with the kit so i will probably have a spare one of these once everything is working.
The 74LS912 also came from Ebay, from the US i think.

I'll go back through all the emails and list the sources, probably Monday at work.
The kit is at work so i'll look at the switchs then as well.

The mainboard as far as i can tell is the same as the ETI board layout, i've not cross referenced the parts list yet, i've been slowly typing it into Excel and reformatting it, separating all the IC's and idetifying the various parts of the circuit so i can work out what extra TTL chips i need to find (mostly from the loft).
The current version of the parts list is here: www.quantums.info/cortex/Cortex Parts list.xls

I've not looked at the power supply at all, the kit i bought seemed to have had all the parts for the power supply pinched including the torroidal transformer so to start with i'm just going to use a small PC power supply.
The seller did mention he had found some assembly instructions but as i belivde they were just reprints of the ETI articles i said not to worry about them.
If the power supply boards are different maybe i can get him to scan them in.
I will check the other side of the power supply PCB i have, i know it was a single sided board but maybe it had silk screen on the other side i didn't notice.

I think that maybe the PCB revision is the small letter after the name marked on the PCB
I have:
Power supply: PSd
Keyboard: KBa
Mainboard: MBb

Jim
 
I bid on the third set of boards as well, as I want to build a machine from scratch to compare to the one I bought off eBay a couple of years ago (missing the floppy controller and E-BUS components). That way I can do some safe smoke testing. . .

On the HTF components, I have a dozen or so of the TMX9909s, a few hundred TMS9901s and TMS9902s, a couple of TMS9911s (no extras there), and a few dozen of the 74LS612s. I use a lot of TI components for other projects, so I tend to keep them on hand if I can get an OK price on them.

BTW, the component numbering on my board doesn't match the ETI numbering either--that change seems to have occurred relatively early in the production run.

I also have to put up a later ETI article I found on a video fix for the Cortex (from 1987).
 
Hi Stuart,
This is where i bought the additional chips from.
No comments on the prices please !, i didn't pay quite that much for the TMS9911.

TMX9909 http://www.electricstuff.co.uk/forsale.html (none left).
TMS9902 http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=220821398049
TMS9911 http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=150583219031
74LS612 http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=330538234440

No joy at all on the 72LS2001 but there seems doubt that they even existed.

I looked at the keyboard switchs and there is no identification on them at all.
I had a quick look through RS and Farnell to see if i could spot anything that looks the same but i couldn't see any.
I will take some close up pictures of them later if it will help.

Jim
 
5 bidders pushed the price up to £41.00, maybe someone could make a batch of ten boards to sell on ebay, updated to use 512KB static ram and other (comparatively) easy to obtain parts, and using a pic to convert the data from a standard PC keyboard to whatever data the cortex rom expects.

@Ksarul, I have only seen the TMS9995 in an ebay ad for £140, is it available for significantly less from the sources you use?
 
mnbvcxz said:
5 bidders pushed the price up to £41.00, maybe someone could make a batch of ten boards to sell on ebay, updated to use 512KB static ram and other (comparatively) easy to obtain parts, and using a pic to convert the data from a standard PC keyboard to whatever data the cortex rom expects.
Click to expand...

Makes me feel a bit better about the price i paid for the first set bought off ebay (before i found out he had more than one set).
Has anybody managed to find out how he got all the Cortex bits, i did ask but got no reply.

Jim
 
mnbvcxz said:
5 bidders pushed the price up to £41.00, maybe someone could make a batch of ten boards to sell on ebay, updated to use 512KB static ram and other (comparatively) easy to obtain parts, and using a pic to convert the data from a standard PC keyboard to whatever data the cortex rom expects.
Click to expand...

This has been suggested with most rare computer forums i'm on.
But, at what point would you stop upgrading it ?
You could put a complete Cortex into a logic array chip nowadays (has been done with BBC's etc).

There are projects to use a Pic to convert a PS/2 keyboard to a parallel interface using a PIC (or other micros) on the net, i've been meaning to build one for my Microtan 65.
The parallel keyboard interface was quite common on early computers.

Jim
 
@mnbvcxz, I got the last 8 TMS9995 chips I bought for $7 each about a year ago. The source shows up on eBay every once in a while with various TMS99XX parts that he gets from other industrial sources as overstock. He had some TMS9995s up a couple of months ago for $5 each and a single buyer nabbed them all (5 of them, IIRC). Patience is key here, as he comes up with stuff pretty regularly. He goes by RJJLROS, and I've never had a problem with his product.

@Jim Hearne, I'll try and get a PDF of the video fix file up where you can grab it sometime this week.

The Cortex seller was somewhat surprised at the level of interest in them, due to the relative obscurity of the Cortex in general. There aren't a lot of us out there with systems, but it is definitely good to see that it is still alive! I'm just glad they ended up in the hands of folks who would build them and increase the population of surviving Cortices, instead of off in a rubbish bin somewhere.
 
Jim Hearne said:
Has anybody managed to find out how he got all the Cortex bits, i did ask but got no reply.
Click to expand...

Pure conjecture but ... from the return address on the package, the company he works for does non-destructive testing, and has been around since 1985. I wonder if they were bought to be used with instrumentation, but got pushed to the back of a cupboard and have been there ever since?

Stuart.
 
I've put on my web site a PDF of the cortex schematics which i've separated from the copies of the Powertran build manual (anotated ETI articles) that were on the FTP site.
These seem to tie up with my rev B mainboard but not the power supply board.
I added R74 and R75 names to the cpu schematic but apart from that they are the same, just in a easier to reference format. (IMO)

http://www.quantums.info/cortex/Cortex schematics-updated.pdf

Fitted the first components to my PCB's today, 80 odd ceramic decoupling capacitors.

I hopefully have a decent scan of the Issue of PCN that had the Cortex 2 review in it coming in the next day or 2.

Jim
 
I've dug out my collection of ETI's and started scanning them onto the PC.
About 20 mins per issue if you have a scanner with a sheet feeder and a Guillotine.
I've found my copy of the ETI Electronics digest that had reprints of the Cortex build in it.
It seems to have the updated Schematics and parts lists.
I've put just the Cortex pages here:
http://www.quantums.info/cortex/Cortex build-Electronics Digest version.pdf
If you want the whole magazine let me know.

I've almost 2 complete sets of ETI's from around 1982 to 1992, the full set i'm cutting in half and scanning.
Does anybody want the other set ?
Unfortunatly only one copy of the original Cortex issue.

Jim
 
I've now got a copy of some more Cortex 2 build documents, these include the new smaller power supply board layout and parts list.
Will scan and upload tonight.

Jim
 
E-Bus Floppy Disk (and other) Cards

E-Bus Floppy Disk (and other) Cards

Just pointing out the availability of E-bus floppy disk and other cards at bargain prices:

http://quarndon.co.uk/index.php?main_page=index&cPath=54_55

I'm guessing that an external floppy disk controller will need changes to any floppy software as the controller hardware address will probably be different to the internal controller ...?

Stuart.
 
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