Need help fixing Oric 1

If you want to ask questions about how the machine works, peculiar details, the differences between models, here it is !
How to program the oric hardware (VIA, FDC, ...) is also welcome.
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kenneth
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Re: Need help fixing Oric 1

Post by kenneth »

Normally the chips have supports, I designed the pcb to install a ZIF support for those who want to program the Uvprom.

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Re: Need help fixing Oric 1

Post by cslee_work »

Question for mikeb or anyone. I burned the 60Hz debug rom and booted.with it. It says RAM PASSED. I see it asks me to press NMI to proceed. I quess it's the reset button at the bottom. Pressing it does nothing however.

The screen stays rock solid. So that's good

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Re: Need help fixing Oric 1

Post by cslee_work »

Ignorr that last question. It was a hardware failure. The clock mod failed. So no clock to ULA.

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Re: Need help fixing Oric 1

Post by cslee_work »

So the debug ROM runs but it FAILS the CASS O/Rly/Spkr. The test does not progress anymore from there. Is it hung ?

I can hear a pulsing tone with the loopback connector.

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Chema
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Re: Need help fixing Oric 1

Post by Chema »

Just as a side note in case it helps, there is a pdf with a guide to use Mike's Rom in his site (see the documentation link at http://oric.signal11.org.uk/html/diagrom.htm)

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Re: Need help fixing Oric 1

Post by mikeb »

cslee_work wrote:
Fri Jul 03, 2020 7:23 am
So the debug ROM runs but it FAILS the CASS O/Rly/Spkr. The test does not progress anymore from there. Is it hung ?

I can hear a pulsing tone with the loopback connector.
Then press NMI to move on :) (It really should say "Press NMI to continue" on screen ...)

From my comments in source "Timeout 20 cycles (about 14 secs)" -- so if you can't hear the beeping, it will give up. If you can hear the beeping, press NMI.

The reason for using the NMI button for everything is that

1) a working keyboard assumes an awful lot of stuff works: the VIA chip, the PSG (Sound chip), and some additional logic on the keyboard itself
2) Required me being bothered to write code to do all that from scratch (nope!)
3) In some cases the bare board being prodded doesn't even HAVE a keyboard
4) Being face down pressing a key is awkward anyway.

But, it always has an "ANY" key (the reset/NMI button) which is really stupidly simple to read, almost is impossible to fail, and so solves all that in one go.

Remember that I was writing this in assembler, working from the paranoid viewpoint that maybe EVERYTHING is broken, so assume nothing can be relied on. As the tests go through, bits that seem to work are used to test bits that are not yet known ...

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Re: Need help fixing Oric 1

Post by cslee_work »

Ok. That's clear now.
All the tests passed. I had to change 6502. Somehow the NMI pin is always low. With a new 6502 all tests passed.

Thanks everyone for the help.

Now if I can find a replacement NMI button, my ORIC is good as new.

Hope I can do the 60Hz fix for the Erebus ROM.
That's for another day when I get it.

Kenneth, can you provide location in ROM to fix it?

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Re: Need help fixing Oric 1

Post by mikeb »

cslee_work wrote:
Sat Jul 04, 2020 12:48 am
Somehow the NMI pin is always low

Now if I can find a replacement NMI button, my ORIC is good as new.
There is no part number shown in the service manual for this switch, but any momentary action normally-open switch would do here. It's a bonus if it fits directly into the PCB holes, but if not, there are many PCB mount mini tactile switches that could be mounted in place (small fragment of 0.1" vero/matrix board, two firm pins aligned to go down into Oric's PCB, mount the switch onto the PCB, wire the switch to the pins, job done).

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Re: Need help fixing Oric 1

Post by cslee_work »

I guess that will work if I can't restore it to stock

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Re: Need help fixing Oric 1

Post by kenneth »

cslee_work wrote:
Sat Jul 04, 2020 12:48 am

Kenneth, can you provide location in ROM to fix it?
In the Erebus file the Oric Rom code begins at the same place as the Basic11b Rom file, then you must replace these bytes:
Adr $3934:
#1E before, #1C after.

Adr $39CA:
#1A before, #18 after.

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Re: Need help fixing Oric 1

Post by cslee_work »

Thank you Kenneth.

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Re: Need help fixing Oric 1

Post by cslee_work »

kenneth wrote:
Sat Jul 04, 2020 9:47 pm
cslee_work wrote:
Sat Jul 04, 2020 12:48 am

Kenneth, can you provide location in ROM to fix it?
In the Erebus file the Oric Rom code begins at the same place as the Basic11b Rom file, then you must replace these bytes:
Adr $3934:
#1E before, #1C after.

Adr $39CA:
#1A before, #18 after.

Kenneth,
Can I program it into a AM28C256? Will it work in place of the 27C512?

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Re: Need help fixing Oric 1

Post by kenneth »

In this case A14 replaces A15 on pin1, this is not a problem for the selection of bank0 and bank3, but the pine27 is problematic with the process, this pin must be disconnected. For the program, Bank0 is the same but Bank3 become the bank1. The content $C000 to $FFFF in the 27c512 chip is placed at $4000 to $7FFF in the 28c256 one.

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Re: Need help fixing Oric 1

Post by cslee_work »

kenneth wrote:
Sun Jul 12, 2020 7:14 am
In this case A14 replaces A15 on pin1, this is not a problem for the selection of bank0 and bank3, but the pine27 is problematic with the process, this pin must be disconnected. For the program, Bank0 is the same but Bank3 become the bank1. The content $C000 to $FFFF in the 27c512 chip is placed at $4000 to $7FFF in the 28c256 one.
Pin 27 can be taken care of easily by not inserting into the socket but pull up to pin28.
Do I need to rearrange the banks in the programming of 28C256?

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Re: Need help fixing Oric 1

Post by cslee_work »

Kenneth,
If I put the 28C256 inside the oric instead of the ORIC ROM, will the Erebus still work, that is the erebus contains no EPROM.

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