Page 2 of 3

Re: Oric-1 Repair

Posted: Sun Apr 28, 2019 2:33 pm
by Chema
The ULA is still available on eBay, I think https://www.ebay.com/p/HCS10017-ULA-IC- ... /623066550

Re: Oric-1 Repair

Posted: Sun Apr 28, 2019 3:15 pm
by Vyper68
Thanks Chema just bought one :D

Re: Oric-1 Repair

Posted: Sun Apr 28, 2019 6:32 pm
by mikeb
Vyper68 wrote:
Sun Apr 28, 2019 1:34 pm
... 6502 and 6522's out ....
I hope that's 6502A (and 6522A, too?) as a plain 6502 is too slow.

The clock may say 1MHz, but it's a lopsided square wave, with the 6502(A) having to complete in about 1.5MHz-worth of time to get out of the way for the ULA to get two bites at memory.

Be warned :)

Good find on the ULA, there's a few people selling them on eBay.

Re: Oric-1 Repair

Posted: Mon Apr 29, 2019 8:18 pm
by Godzil
mikeb wrote:
Tue Apr 23, 2019 5:08 pm
1) Powered it with a totally inappropriate adapter (AC output, wrong polarity, 12V or even higher etc).
The only thing that may die here is the 7905 and yet; they are quite robust. Never manage to kill one even with reverse polarity.

The second point is more likely (the power jack in the ext connector) especially considering what pin 33 and 34 are and they are just next to the power socket...

Re: Oric-1 Repair

Posted: Tue Apr 30, 2019 2:45 am
by Equinoxe
mikeb wrote:
Sun Apr 28, 2019 6:32 pm
Vyper68 wrote:
Sun Apr 28, 2019 1:34 pm
... 6502 and 6522's out ....
I hope that's 6502A (and 6522A, too?) as a plain 6502 is too slow.

The clock may say 1MHz, but it's a lopsided square wave, with the 6502(A) having to complete in about 1.5MHz-worth of time to get out of the way for the ULA to get two bites at memory.

Be warned :)

Good find on the ULA, there's a few people selling them on eBay.
Is the 6502AP equivalent to a 6502A for the purposes of use in the Oric?

Re: Oric-1 Repair

Posted: Tue Apr 30, 2019 6:14 pm
by mikeb
I think the "P" is for plastic (packaging suffix) :)

It's the "A" that's the important letter. You got an "A", you're ok.

Re: Oric-1 Repair

Posted: Fri May 17, 2019 6:47 pm
by Vyper68
Well I have all the chips in hand now and have got it living again - up to a point. I tried it with the Diagnostic ROM to test the RAM ( which passed ) and got the screen Test Cards ( both ). Then next time I power cycled I get vertical black and white bars and it stays like this each time I power cycle thereafter.
I need to do some more modifications to the board as it had had no service modifications when it arrived. I think it might be the EPROM that is the problem but it's a normal 27c128 burned with 1.1B and it works in my Atmos OK. Can anyone tell me what they think it may be? am I looking at the right area?
I fitted a 65c02 and cut pin 1 but I still need to put a wire between pins 2 and 36.

I've gone this far with this little Oric I don't want to give in now as I have practically built it from the ground up.

Re: Oric-1 Repair

Posted: Fri May 17, 2019 10:19 pm
by Chema
Remember the Oric is a bit picky when booting. Plug the PSU first, then the plug into the Oric (careful: do not plug it into the expansion port!). With some Orics it may need more than one attempt,

Some service modification improved the booting cycle, though, IIRC.

Re: Oric-1 Repair

Posted: Sat May 18, 2019 11:28 am
by Vyper68
Yeah Chema, will keep at it and eventually i'll have a working Oric-1, it would have been cheaper to buy one after the amount I have spent on replacement EPROM's, CPU,VIA and RAM.
Wouldn't have been as much fun though :wink:

Re: Oric-1 Repair

Posted: Sat May 18, 2019 5:32 pm
by mikeb
After powering it up (at the wall, and plugging in), if you get nothing beyond the black-white bars, try briefly shorting pin 40 of the CPU (Reset) to any ground point (e.g. Pin 1 or 21 of the original CPU or pin 1 of 6522 -- I don't know the significance of the pin-1-cutting comment you posted, but I assume P1 must have been reused on a 65C02, and P21 must therefore still be 0v, otherwise how is it powered? :)

This will force a reset, manually, once the power supply is definitely stable. If this works, you have a power-up-reset timing problem, in that the CPU is either not getting reset, or reset too quickly (before power is settled, before the ULA is clocking properly) -- in which case look at replacing C21 (1uF/10v) which might have aged.

Re: Oric-1 Repair

Posted: Sat May 18, 2019 9:20 pm
by Vyper68
The 6522a I bought didn’t work diagnosed thanks to your ROM mikeb, I fitted another one and it works now With the pin 1 disconnected and pins 2 and 36 jumpered and the 65c02 and works fine. So now the Oric-1 works although the left and right shift keys do not work on all keys I can get by using alternate shift keys to cover the entire keyboard. So this Oric is pretty new from the ground up.

Re: Oric-1 Repair

Posted: Sun May 19, 2019 1:59 pm
by Vyper68
Last night's post was a bit short on detail so I will add more. So I had replaced the Logic IC's and also the 12Mhz Clock. I also replaced the three transistors and the diode on the relay just in case they were damaged as I had spares available. I burned MikeB's Diagnostic ROM and the first time I got a RAM test pass then the machine would not boot again. Character wide vertical Black and White bars, so I thought the ROM was the problem but looking on the thread about fitting a 65c02 there was a note about not connecting pin 1 and connecting pins 2 and 36. I followed this advice and then it would boot beyond the character wide Black and White bars to 2-3 pixel wide Black lines on a White background, almost as if it was trying to boot. I fitted the Diagnostic ROM again and the RAM and ULA passed OK and then the VIA would fail. I fitted a new 6522P ( which i did not expect to work ) and the VIA test passed up to PORT A as I had not built the Printer Loopback. So I fitted the 1.1B EPROM i had burned again and there it was ... ORIC 1.1 BASIC :D
The joy was short lived as the keyboard did not work. So I took it all apart again, I knew the AY chip was good as I used it for my Spectrum Melodik 2 AY Sound PCB so that could not be the problem. So i replaced the 4051BE chip on the Keyboard PCB and now the keyboard works ( albeit with odd restrictions as detailed before )
So I have basically replaced every IC on the PCB and the one on the Keyboard as well so this has been the most challenging repair I have undertaken on any 8-Bit and was a very steep learning curve but ultimately very pleasing to save an Oric-1 from oblivion.

Re: Oric-1 Repair

Posted: Sun May 19, 2019 2:57 pm
by Chema
Impressive work. Congratulations!

Re: Oric-1 Repair

Posted: Sun May 19, 2019 8:05 pm
by mikeb
Vyper68 wrote:
Sat May 18, 2019 9:20 pm
although the left and right shift keys do not work on all keys I can get by using alternate shift keys to cover the entire keyboard.
That is a pretty odd symptom.

The shift keys (and FUNC, CTRL) are on a common "column" of the keyboard matrix, with nothing else. So are you seeing any problem with CTRL-(anything) ?

Any danger that there is a bad connection between the keyboard PCB and main PCB at the connectors/soldered joints?

Can you see any pattern to it, in that the left shift does work on (x,y,z) but not on (a,b,c), meanwhile the right shift ... are there any keys that both work on, or neither work on?

I'm glad you've got this far, it's a massive repair!

Re: Oric-1 Repair

Posted: Mon May 20, 2019 5:37 am
by Vyper68
Yeah I’m going to have a look today at the traces and solder joints. The right shift key doesn’t work on 8,10,-,= and the left shift doesn’t work with , . And /
Going to look at the keyboard PCB as well today but I haven’t tried the Ctrl key yet.