forum.defence-force.org

Thanks for the program and advice. I typed in and ran the program and it appears there are no further problems. I let the program run for 49 passes and no error was generated so conclude the RAM is okay. Unfortunately, I mixed up the RAM I removed, by accident, so not sure which of the 4164s is the ...

It does look like it's something to do with the RAM. I replaced all of the RAM with 4164-15 which were bought from a reputable seller. I tested the RAM before installing the ICs and all was good. However, I guess the tester only checks it can read/write and doesn't check speed or maybe one of the 41...

Tried the PCB out of the case and unplugged from the keyboard. Tried powering up the computer and get the following line displayed after 27-30 seconds (no pressing of board). corruption.png The line doesn't appear in the same place, sometimes it's above and below shown in the picture. Tried this six...

An almost there update. The keyboard problem turned out to be with the keyboard cable as some of the wires had detached from the keyboard PCB. Didn't take too much before the cable came away from the PCB. Trying to bare the wires on the cable was a nightmare and in then end had to splice a ribbon ca...

Think I've found the problem and it's a bit of bad luck. Checked the VIA socket for continuity and found pin 32 of the VIA socket is not connected. The picture below is a close up and I've highlighted the problem pin. Looks like the solder didn't make it to the pin or the pin is just a little bit sh...

Just tried the computer with the keyboard plugged in and the letter K is displayed repeatedly when the computer is turned on. Sometimes a carriage return must happen because the cursor moves down a line randomly and not wrap. I've tried the mjb test108 ROM and it gets to the VIA test page and displa...

Made progress and found the problem. The problem was one of the 74LS04s was bad (IC21). I replaced the 74LS04 and powered up the Oric with iss' ROM but didn't hear any sound. However, screen pattern was different. Reset the computer and saw a familiar pattern of mostly black screen with white horizo...

Just a small update. Got a new AY-3-8912 and fitted it. Checked board resistance and get 217 Ohms with all chips but RAM inserted. With the old AY-3-8912 I could hear a very quiet clicking/popping sound coming from the speaker when iss' diag ROM inserted. With the new AY-3-8912 inserted there's no s...

Fitted a new LM386 but it didn't make a difference to the loudness of the audio. Gives more substance to the problem being the AY-3-8912. I've got a replacement AY-3-8912 on the way.

2 steps forward ... Have an update where I think the Oric is partially working but still has problems. I have removed and socketed the AY-3-8912, and replaced the ROM socket because it looked a bit poor. I measured the resistance with the AY-3-8912 removed from the board and got a resistance of arou...

I've measured resistance between 5v and GND and it's around 150 ohms. I'm guessing this isn't good.

Just tried the diag ROM with all of the RAM removed and still no sound. However, not tested the speaker and just assuming it works. The image on the screen has changed where instead of small green rectangles that jitter they have turned to purple spots that jitter.

I removed the IDC connector as found a direct short between pin 18 and 5v. Had a similar problem with a BBC micro where one of the pins was shorted and reflowing the connector (BBC micro) fixed the problem but didn't with the Oric so removed the connector to see if there was anything obvious under i...

Here are pictures of the board as it currently is. I've had to change capacitors C23 (it broke) and C1. Atmos bottom.jpg Atmos top.png Gone backwards as don't get a stable picture anymore. Turn on the computer and the vertical lines are back and scroll up the screen and jitter. Touching/tapping the ...

Okay, I'll get some pictures later. Only the ROM was in a socket. ULA was soldered to the board.