Atmos RAM failure? Need help

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.
Post Reply
User avatar
kppot
2nd Star Corporal
Posts: 27
Joined: Fri Mar 19, 2021 2:28 pm

Atmos RAM failure? Need help

Post by kppot »

Hello,
Recently I bought Oric Atmos off eBay as "not tested". Upon powering on it greets me with a typical black-white RAM failure screen.
B908A053-0788-48CE-A8B5-60251ED7F65F.jpeg
I would simply replace RAM chips, as many cases described before me, but it comes also with some humming noise from the speaker, so I suspect there is something else to replace. Any suggestions or advices please?

A similar post was about affected 6502, so I am afraid it would be not that simple
https://forum.defence-force.org/viewtop ... 7&start=45

In the meanwhile my picture is close or similar to this case (RAM failure)
https://forum.defence-force.org/viewtop ... f=8&t=2029

Cheers

PS cannot burn test ROM atm :(

User avatar
kppot
2nd Star Corporal
Posts: 27
Joined: Fri Mar 19, 2021 2:28 pm

Re: Atmos RAM failure? Need help

Post by kppot »

Alright since none was interested I began to actually repair it
Few chips were already socketed, so I removed only soldered ones
Then a clean with ISP, just in case. All holes were checked with the pin, all tracers were buzzed for continuity.
IMG_8772-20-03-21-06-59.JPG
4 sockets installed and filled with Russian RAM chips, borrowed from my Pentagon 128
After powering up the noise described above was present but in a matter of 1.5-2 seconds it became significantly silent, and I was greeted by booted machine
FullSizeRender-20-03-21-10-28.jpg
A flawless victory!
Next step is a proper SD solution and SCART cable
Still that noise is very annoying, any tips to make it silent? Or it is an Atmos feature - never had an Oric before. :?
Any ideas or hints?

User avatar
kppot
2nd Star Corporal
Posts: 27
Joined: Fri Mar 19, 2021 2:28 pm

Re: Atmos RAM failure? Need help

Post by kppot »

Alright, reading suggest it is a feature, and it sounds exactly like this

http://www.mirari.fr/ZobC?a=open

So I should replace C1, C8 and C21 just to be sure

User avatar
Dbug
Site Admin
Posts: 3672
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Re: Atmos RAM failure? Need help

Post by Dbug »

kppot wrote:
Sat Mar 20, 2021 8:37 pm
Alright since none was interested I began to actually repair it
It's common that people look at the forum only every few days, or that nobody posts anything for three or four days :)

User avatar
Chema
Game master
Posts: 2794
Joined: Tue Jan 17, 2006 10:55 am
Location: Gijón, SPAIN
Contact:

Re: Atmos RAM failure? Need help

Post by Chema »

I was about to suggest you replace RAM and the RAM multiplexers. Those are nearly always the culprits with such symptoms. You simply were too fast :D

User avatar
kppot
2nd Star Corporal
Posts: 27
Joined: Fri Mar 19, 2021 2:28 pm

Re: Atmos RAM failure? Need help

Post by kppot »

Dbug wrote:
Sat Mar 20, 2021 9:40 pm
It's common that people look at the forum only every few days, or that nobody posts anything for three or four days :)
Yeah, it is me who is quite impatient in fact :roll:

User avatar
kppot
2nd Star Corporal
Posts: 27
Joined: Fri Mar 19, 2021 2:28 pm

Re: Atmos RAM failure? Need help

Post by kppot »

Chema wrote:
Sat Mar 20, 2021 10:01 pm
You simply were too fast :D
Yes, as I was impatient to start the machine properly
Thanks for your help though

Post Reply