Oric 1 and Atmos - repair help needed - EDIT: Oric 1 works

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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YuT666
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Re: Oric 1 and Atmos - repair help needed

Post by YuT666 » Thu Jan 05, 2017 2:36 pm

Voltage of both 7905 is 4,9V.

I checked the main ICs and they are getting 4,9V too ...

So i should write a checklist:
- working power supply - OK
- 7905 and main chip voltages - OK
- ROM chip (i changed the ROM, but a had the same problem) - OK
- 6502 - reset pin - first low and then high - OK
So i'll go on with checking some things in the oric service manual and trying to shorten the cap C21 pins (thanks iss).

EDIT: Shorting C21 - only a gentle noise and the result is the same.

EDIT 2: Maybe i should replace the C21 capacitor.

EDIT 3: I'm losing my temper and i want to throw this garbage to the wall ... i checked pins 14/2 of all DRAMs and all are different between 2.35 and 3,30V. they should be about 4V or am i wrong?

I searched and searched the net for a better failure documentation, 'cause i DON'T cut any lines. I don't know, what i should measure exactly and what to do now. Desoldering a 40 pin IC is a bit too difficult and piggy back isn't recommended here, i think.

Maybe the whole thing is not my cup of tea, i should stay with my Thomsons.

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Re: Oric 1 and Atmos - repair help needed

Post by iss » Fri Jan 06, 2017 12:20 am

YuT666, gib dich nicht auf, bitte! ;)

I had the same problem with one Oric from eBay - here is what happened with it: Oric Atmos from scratch. Now (2 years later) it works and it looks cool :)
20170106_000549.jpg
The problem was broken track under the RAM chips. I used it to try to produce the picture of your Oric and the closest is when I remove one of the: right-most-RAM, ROM or CPU:
20170106_000240.jpg
It would be best if you have spare RAM,ROM and CPU.
Because the PCB is more valuable than the chips, you need to (very carefully) cut the chip pins and then it's easy to desolder and remove one-by-one pins. Use sockets for the new chips.

But before this, I prepared today simple diagnostic ROM - attached file contains 2k and 4k versions - you can burn it on 2764 or 27128 (better in your case!) EPROM. This diagnostic ROM does NOT use RAM at all - if CPU,VIA,PSG, LM386 amp and speaker are OK - you can hear sound like phone busy signal :)
It works in Oricutron and tomorrow I'll test it on my PCB (first I have to solder some missing analog parts).
diag-roms.zip
(681 Bytes) Downloaded 28 times
Additionally, can you measure with Ohm-meter the resistance between pins 7(-) and 14(+) of the missing chip labeled IC11? It should be 250-260 Ohms or 350-360 Ohms.

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Re: Oric 1 and Atmos - repair help needed

Post by YuT666 » Fri Jan 06, 2017 1:17 pm

Thanks for your help ...

I think, that it could be a 6522 problem. I have spare 6502 and 6522 from some old commodore 1541 floppys ... and 'cause i don't like commodore hardware, i can the ICs for the Orics.

It is really disturbing, 'cause both Orics have errors.

I don't have a eprom burner, so i have to wait for a pal. He isn't there the next days.

Your wrote ...
you can hear sound like phone busy signal
I can hear a sound like this, when i power up the Orics (with diagnostic rom and without), but i don't know, what sound do you mean EXACTLY.

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Re: Oric 1 and Atmos - repair help needed

Post by iss » Fri Jan 06, 2017 1:23 pm

YuT666 wrote:..you can hear sound like phone busy signal
This tone will be generated with the above attached diag rom when burned on EPROM and inserted instead the standard rom.

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Re: Oric 1 and Atmos - repair help needed

Post by YuT666 » Fri Jan 06, 2017 5:03 pm

I don't get any values (pins 7 and 14 of the missing chip labeled IC11).

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Re: Oric 1 and Atmos - repair help needed

Post by Godzil » Fri Jan 06, 2017 9:59 pm

If it stay on the ram test pattern, it's probably the 6522 or the AY-3-8910

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Re: Oric 1 and Atmos - repair help needed

Post by YuT666 » Sat Jan 07, 2017 12:07 pm

Desoldering a 40 pin IC is too difficult (and we all don't know if the 6502 or the 6522 are really defective). Too much risk for a damage even with my good equipment. I will leave them as they are and put them back in the rack.

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Re: Oric 1 and Atmos - repair help needed

Post by Godzil » Sat Jan 07, 2017 4:52 pm

For me, the 6502 is perfectly working as we have a test ram pattern on screen.

Does the 6522 gets hot?

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Re: Oric 1 and Atmos - repair help needed

Post by YuT666 » Sat Jan 07, 2017 5:21 pm

Not really hot, i would say warm ...

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Re: Oric 1 and Atmos - repair help needed

Post by Chema » Sat Jan 07, 2017 5:26 pm

Why do you say that Godzil? Honest question from me trying to learn something :)

If the 6502 gets stuck due to malfunction you'll continue seeing those strips on screen as the ULA is using the memory contents before the ROM actually fills the memory with some value (writes/reads $AA and $55 to every memory address), but that is not the pattern you see on boot. The first things that the 6502 runs are related to setting up the stack pointer, enable interrupts and clear decimal flag, then goes on with the initialization. That is in the ROM. If the 6502 does not work and halts, or there is a problem with the board tracks and memory is wrongly read (for instance) you can get this problem.

Couldn't it be just some bad capacitor or soldering preventing the 6502 to boot as it happens many times when the oric refuses to boot at first and have to plug/unplug the jack??? It is the same symptom.

EDIT: In fact the init routine in ROM uses page 0 as pointers, so any error in a memory chip affecting the addresses used and you may end up with an infinite loop, preventing the machine to boot. I guess that is why the Oric FAQ says that if the Oric gets stuck at the stripes screen best guess is the PSU, then a damaged memory chip. If you have replacements, maybe piggybacking may give a clue... but fist let someone with hardware knowledge to tell....

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Re: Oric 1 and Atmos - repair help needed

Post by Godzil » Sat Jan 07, 2017 7:00 pm

Chema wrote:Why do you say that Godzil? Honest question from me trying to learn something :)

If the 6502 gets stuck due to malfunction you'll continue seeing those strips on screen as the ULA is using the memory contents before the ROM actually fills the memory with some value (writes/reads $AA and $55 to every memory address), but that is not the pattern you see on boot. The first things that the 6502 runs are related to setting up the stack pointer, enable interrupts and clear decimal flag, then goes on with the initialization. That is in the ROM. If the 6502 does not work and halts, or there is a problem with the board tracks and memory is wrongly read (for instance) you can get this problem.

Couldn't it be just some bad capacitor or soldering preventing the 6502 to boot as it happens many times when the oric refuses to boot at first and have to plug/unplug the jack??? It is the same symptom.

EDIT: In fact the init routine in ROM uses page 0 as pointers, so any error in a memory chip affecting the addresses used and you may end up with an infinite loop, preventing the machine to boot. I guess that is why the Oric FAQ says that if the Oric gets stuck at the stripes screen best guess is the PSU, then a damaged memory chip. If you have replacements, maybe piggybacking may give a clue... but fist let someone with hardware knowledge to tell....
I agree, but the pattern we see on the two screen on the original post are not random data, or only zero. (and they happen everytime)

Edit: ok I'm wrong a bad 6522 will get up to the point of the screen filled with the A5 test patter, hum..
That does not explain the pattern on screen, for me the first was more Oric1 and the second Atmos, but the only (real) difference between the two is the ROM..
Weird, it's clearly not from the ROM :/

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Re: Oric 1 and Atmos - repair help needed

Post by Chema » Sat Jan 07, 2017 9:39 pm

The Atmos has the usual pattern. The Oric 1 has one I don't remember having seen, but it was certainly the one for the first Oric-1s. You can mimic this behavior by changing the ram pattern entry in the configuration file in Oricutron.

It was related to the memory being used or the circuitry or something like that. I read that somewhere...

It would be nice to see if there is any activity in the 6502, maybe address lines with a Logic analyzer or something...

A broken ULA may hang the machine in this way, as it generates many signals, but it'd be the first time I see this, and in two machines ath the same time! Not too probable.

Again, usually the 6502 doesn't break this way.

But maybe the owner plugged in something ans blew up a multiplexor or some other chip which may cause havoc. And did it in both machines. What about plugging in a PSU with the wrong polarity? That would be a sensible cause for damaging two Orics in the same way, and both came with no PSU. What could be blown up this way? It may be worth checking those components...

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Re: Oric 1 and Atmos - repair help needed

Post by Symoon » Sat Jan 07, 2017 9:53 pm

Chema wrote:The Oric 1 has one I don't remember having seen, but it was certainly the one for the first Oric-1s.
I do confirm, it was the one of my Oric-1, one of the early ones with grey logo.
Also available on Euphoric with ram pattern = 2 (in euphoric.ini configuration file)

Useful to test programs as it changes some default RAM content after booting, which can affect programs that don't initialize their values at start ;)

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Re: Oric 1 and Atmos - repair help needed

Post by Godzil » Sat Jan 07, 2017 10:53 pm

Chema wrote:The Atmos has the usual pattern. The Oric 1 has one I don't remember having seen, but it was certainly the one for the first Oric-1s. You can mimic this behavior by changing the ram pattern entry in the configuration file in Oricutron.

It was related to the memory being used or the circuitry or something like that. I read that somewhere...

It would be nice to see if there is any activity in the 6502, maybe address lines with a Logic analyzer or something...

A broken ULA may hang the machine in this way, as it generates many signals, but it'd be the first time I see this, and in two machines ath the same time! Not too probable.

Again, usually the 6502 doesn't break this way.

But maybe the owner plugged in something ans blew up a multiplexor or some other chip which may cause havoc. And did it in both machines. What about plugging in a PSU with the wrong polarity? That would be a sensible cause for damaging two Orics in the same way, and both came with no PSU. What could be blown up this way? It may be worth checking those components...
Honestly if there is display, the ULA have a high chance to work fine.

The 6502 can break, I have an Oric with a dead 6502.. :/
(poking random metallic thing in the expansion port is a good way to kill the CPU.. :/)

The 7905 protect the Oric from reverse polarity, so at worst it would die, at beat it does nothing (and get really hot).

Edit: YuT666, you have measure the voltage, which is fine, but could you measure the current ? That would also give an idea, if it's really high that may mean something is dead but not short circuit (or the 5V rail would be a 0V), if I remember correctly a normal working Oric should be between 400 to 600mA on the 9V side (yeah that thing is really hungry..)

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Re: Oric 1 and Atmos - repair help needed

Post by YuT666 » Sun Jan 08, 2017 11:14 am

Thanks, but what do you mean? The current what?
you have measure the voltage, which is fine, but could you measure the current ?

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