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Powertran Cortex

Fantastic news Nige, -- this could possibly be a glimmer of light at the end of the tunnel !!!

I'll look out for the delivery and keep you posted - Many Thanks
 
A positive update for a change!

Nige, I received your DRAM chips today and tried 8 of them together with the Forth Eproms. This gave me the Forth screen prompt and I actually ran a quick forth test routine for the first time in 20 years!
I then re-fiited the originals, one at a time and found to my suprise that 5 of my 4164s were faulty.
I then installed the new Basic Eproms and got the original problem with the same LED sequence and the continual tone.
So Stuart, it looks like you were spot on with your prediction.

I then dug out my original Basic eproms (Couldn't remember which one was faulty - Thought it was IC45) and tried different combinations of new and old eproms but stiil had the same fault.

But a great leap foward and my system is now working on Forth thanks to all of you.

So to the next step -

Where can I get some 4164s or MCM6665s or equivalents and where would be the best place to look - or Nige, can I buy 5 off you.

Also if I post the new basic eproms back to you together with my originals, would you mind testing them on your system for me.

One last question, the new Eproms were labelled

Cortex 1 EB84
Cortex 2 149E
Cortex 3 72EB

and I put them in sockets 47, 46, 45 respectively, as instructed but what are the hex digits, are they eprom checksums or do they refer to a memory map?
 
Good news so far, it is a bit like pulling teeth though.
1) the 6665s were yours anyway, I had a fair size pot full, now (with a little shaking) I can fit them all into the same "racco drawer"
2) now I know my basic eproms work, I can get some known good images sorted.
3) I'm expecting some TMS2532s for myself through the post any day now, Provided they aren't counterfeit, I could blow another 3 basic roms (to the good images), test them, then send them down. Just send me back your spares when you've finished.
4) the hex numbers are checksums.
 
Nige - Thanks very much for the RAM chips.
I'll send you my 3 eproms in the post today and then you can decide which ones to use.
 
Doh! 2532s aren't 2564s! so yes, good job you sent the basic eproms back.
Full of cold, but I've just had some "Lem-Sip", & will pop upstairs & have a go in a few minutes.
 
Don't worry I am still with you. In order to test the eproms I can't get the safeblock in, which means I'm having to redo the mains bits, using components which are slightly buried. It's taking a bit longer than it should.
 
FINALLY! got the mains bits replaced on my cortex. I was a bit fed up that the hole in the back of the metalwork isn't exactly the right size for an IEC inlet so must be for a long-obsolete switch. I've put an IEC on it, and have to order a little latching push-button to go in the old mains lead hole. It's not too bad a codge, and I hate trailing mains leads.
I've just lifted the roms, slightly awkward, as there are caps and a case in the way. Checked them against Andy's and there's one byte completely wrong in IC47. Erased & reprogrammed.
Andy - I'll pop them in the post tonight, they should go first thing tomorrow morning, and if you're really lucky you'll get them before Easter.

Edit - the lack of vertical sync appears to be down to the TV! I've just tried it on my relic Philips Discoverer, and it's solid as a rock. (?...)
 
Thanks Nige,

I'll let you know how I get on.
I've ordered some new electrolytics to replace the 30 year old capacitors in my power supply, so they should all arrive together.
 
Better add these to the whtech archive...
 

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Nige, Received the Eproms this morning, plugged them in and **** SUCCESS *** a basic prompt appeared on the screen and no irritating tone from the speaker!
Thanks to all your hard work and patience, I now have a working Cortex.
Over the years it has come very close to ending up on the tip. I certainly would never have put money on it ever being coaxed back to life.
Also many thanks to Stuart for his fault finding tips and guidance.

Next stage, after replacing the electrolytics, is to load on the 2 games I have and then save them as WAV / MP3 so you can all have a copy.
 
Hurray! one bad byte can spoil the barrel. (sorry O/T - apple related)

Is it supposed to beep on power up at all? mine doesn't - strange but I can't find the speaker/piezo at all on the diagrams.
 
Nige, I think the piezo is labelled as "BELL" on IC64 (Q6) - See ETI - Cortex part 2, Fig 1 (Circuit diagram for keyboard and control port)
On the board it's located 3 x IC sockets to the right of the +12 volt input lead.
 
There's a slightly fried but nevertheless functional resistor attatched to the "piezo" terminals on mine. It's not there anywhere on the cct diags.
Other half of the question - does it beep on power up? (mine doesn't) it's a bit easier than trying to get it to beep in basic to ascertain functionality of the speaker.
It could be like the lack of sync problem I had - which turned out to be the fault of the TV, not the computer.
 
My Cortex doesn't beep at start up either but if you want to test the speaker press the "rub out" key. If you haven't entered any text it will beep each time you press it.
On mine the two piezo circuit board contacts are for the leads to the piezo, the only resistor is to the right of these contacts. = R45
 
Nige/Andy,

I got all warm and fuzzy inside knowing that, out of this, not one but two Cortex's have been brought back to life and we got a copy of Forth as well! Great work to all involved.
 
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