Hi, my Oric 1 has two problems - 1st =80% of the time it powers up garble screen out put and 20% of the time it's ok - 2nd is when it does seem to work the output is Black and white mono chrome ! .. what can make a out put to be mono chrome please ? Thanks.
Really tricky one. Normally garbled screen is due to bad RAM, but grey only sounds more like the video demodulator or the ULA. Sorry about so incomplete a reply. If you have access to an oscilloscope, try to look at the video signal. There should be a colour burst.
Hi, :o) thank you for your reply - Done more testing and these are my findings so far - Oric powers up well IF you plug in the power supply first ! ... 2nd the TV mod out - On my modern TV finds it and there is colour but had interference while there is none on my old Sony 90s portable TV and VHS RF in and scart out to the modern LCD TV shows stable but Monochrome /no colour !...
Hi, :o) thank you for your reply - Done more testing and these are my findings so far - Oric powers up well IF you plug in the power supply first ! ... 2nd the TV mod out - On my modern TV finds it and there is colour but had interference while there is none on my old Sony 90s portable TV and VHS RF in and scart out to the modern LCD TV shows stable but Monochrome /no colour !...
It's funny, but when I bought a broken Oric-1 cheap I was thinking it would be a fun project. Getting it to boot was a matter of replacing failed DRAM IC's but my troubles didn't stop there. I had keyboard problems which required me to replace the AY-3-8912 sound chip buuuuuut.... The later versions don't play nice. Weirdness followed until it clicked that the asymetric clock took the newer version well out of spec!
+NatureAndTech It didn't just affect the keyboard. It also caused the computer to do odd things. Certain keys down the right hand side didn't work. I read on the internet that there were problems and decided to swap it with an older part which fixed it. I still need to make a dump of the TTL PROM for the future though. I'll never be able to buy one of those if it goes pop.
+NatureAndTech The serial attributed are also an odd feature. Lastly, I also made the mistake of putting a socket on thinking I was being clever until the case wouldn't close.
Where can you buy a replacement ULA?
hum bars are usually cause by bad capacitors in the power stage of the PSU
Good point. For an transformer-based PSU, then they are typically synchronous with the screen refresh.
Hi.
Do you know if anyone has made a 'New' Hardware ORIC-1 ..sort of like the Harlequin is to the ZX spectrum ??
Thanks
Unfortunately not.
Hi, my Oric 1 has two problems - 1st =80% of the time it powers up garble screen out put and 20% of the time it's ok - 2nd is when it does seem to work the output is Black and white mono chrome ! .. what can make a out put to be mono chrome please ? Thanks.
Really tricky one. Normally garbled screen is due to bad RAM, but grey only sounds more like the video demodulator or the ULA. Sorry about so incomplete a reply. If you have access to an oscilloscope, try to look at the video signal. There should be a colour burst.
Hi, :o) thank you for your reply - Done more testing and these are my findings so far - Oric powers up well IF you plug in the power supply first ! ... 2nd the TV mod out - On my modern TV finds it and there is colour but had interference while there is none on my old Sony 90s portable TV and VHS RF in and scart out to the modern LCD TV shows stable but Monochrome /no colour !...
Hi, :o) thank you for your reply - Done more testing and these are my findings so far - Oric powers up well IF you plug in the power supply first ! ... 2nd the TV mod out - On my modern TV finds it and there is colour but had interference while there is none on my old Sony 90s portable TV and VHS RF in and scart out to the modern LCD TV shows stable but Monochrome /no colour !...
It's funny, but when I bought a broken Oric-1 cheap I was thinking it would be a fun project. Getting it to boot was a matter of replacing failed DRAM IC's but my troubles didn't stop there. I had keyboard problems which required me to replace the AY-3-8912 sound chip buuuuuut.... The later versions don't play nice. Weirdness followed until it clicked that the asymetric clock took the newer version well out of spec!
Yeah, repairing old computers can be real frustrating, but you got it working in the end. How did the AY-3-8912 affect the keyboard?
+NatureAndTech It didn't just affect the keyboard. It also caused the computer to do odd things. Certain keys down the right hand side didn't work. I read on the internet that there were problems and decided to swap it with an older part which fixed it.
I still need to make a dump of the TTL PROM for the future though. I'll never be able to buy one of those if it goes pop.
Really strange symptoms. Maybe it messed up the address or databus?
+NatureAndTech
The serial attributed are also an odd feature. Lastly, I also made the mistake of putting a socket on thinking I was being clever until the case wouldn't close.
+Duncan Gunn attributed display sorry.