24s10 replacement; and saying hello

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.
MacShrike
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24s10 replacement; and saying hello

Post by MacShrike »

Ls,

Hello fellow defenders. I finally passed all the security checks.
I know Mikaël takes his job very serious but I thought the deep cavity search was a bit much, I won't be able to sit for a week.
Also; did everybody have to submit stool and urine samples?

That beeing said I have a hardware repair question.

I recently started cleaning up my dad's old computer collection.
It has an Oric Atmos in it.
First I fried IC1 with a sinclair PSU :roll: replaced that.
A few keyboard buttons weren't firing.
Opened up the keyboard cleaned it. Now no keys work :?
Resoldered the KB cable. It came of.
Fixed and checked PSU polarity and voltages. They check out now. :wink:

Using the service manual checked the clocks and for sure. The last pin on the last IC (23) had no clock.
Took it out. It looks really battered. I think this Oric has already been salvaged for IC23 and somebody put the old one back. (I vaguely remember my dad saying he picked it up and some keys weren't working back then).

Afcourse it's a PROM.

So long story short:
Does anybody know where to get a replacement for 24s10? Perhaps someone in the force?
The S. Manual states there is an advanced user manual that shows how to make that EPROM in appendix L.
Does anybody have a digital copy of that I could use?

I will not rest until I got this beauty in working order, if only to pay respect to my late dad and make up for not showing an interest back then :oops:

Anyhoe, thanks for reading this far. :D

Happy to be here.
Highest regards, Mac
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Dbug
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Re: 24s10 replacement; and saying hello

Post by Dbug »

Regarding the TSP24S10N, it's apparently only necessary if you are using the TV modulator, and not required if you are using SCART.
See: https://forum.defence-force.org/viewtopic.php?t=1944

My suggestion: Abandon TV modulator and get yourself one of the very good cables like that one:
http://www.retrocomputershack.com/PDF/Oric-Scart.pdf
MacShrike
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Re: 24s10 replacement; and saying hello

Post by MacShrike »

Hi debug,

thank you, thats good news and bad news.
I already made a rgb cable.

I am just following the service manual.
KB doesnt work.
Then it's likely to be the VIA or the sound chip.
I'm new to this hands-on technical stuff.

Since your handle is aptly named dbug.
Could you give me hint how to scope out quickly which of these it is?

Greets,
Mac
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Dbug
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Re: 24s10 replacement; and saying hello

Post by Dbug »

The most common problem with the keyboard is that some have one less connector on one side, so you can easily reposition it incorrectly in which case it will not work.

Other issues are weak solders on the connector (easy to break), or frying the small component on the keyboard that does the matrix decoding.

But one thing at a time, what is the current status, do you have video or not?

Don't try to fix everything at once, the most important is the video, because it's handled by the ULA which is the core component of the Oric, in charge of the video of course, but also refreshing the RAM, and generating the sub-frequencies for the other chips from the main clock. Even if the CPU is damaged, at the very least if the ram and the ULA are properly working, you should have a picture, probably with garbage on it, but a picture none-the-less.

Ideally you want to check all the voltages are correct, that no RAM chip is very warm (probably fried), if you have an oscilloscope, check that you have the proper clock signals at the input of the ULA and 6502.

If that works fine, a good idea is to try to get or make a diagnostic rom, which is a 16KB replacement ROM for the system ROM, it will test stuff one at a time and give you some information.

Also, photos can be helpful to diagnose issues, text is not always the best way to describe a problem.
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