32-bit acorn hardware • Re: Yet another partly dead A5000

My experience trying to overclock Alphas is to the negative - they don't, at all. YMMV, but I'd put the 66Mhz back in if you do still have it - at least for testing - you want the most basic standard machine config you can get to.

That's fair, I'll dig it out.

Yeah, the board will start up and can be used with just 5V applied.

Great.

Yes, "toggleability" means RISC OS is running.

No floppy flashing could mean that the floppy / bus isn't working, and with that amount of delay it could be that it's trying to flash.

I was assuming it was working since it seeks but yes, something else could be wrong there.

Check that you have continuity from the CMOS RAM chip I2C pins to the IOC pins. Check you have power across pins 4 and 8 of the CMOS RAM chip when the machine's on.

I repaired the I2C continuity when I replaced the CMOS RAM chip (those were the only two that seemed to have corrosion issues). They now go through to the appropriate pins on the backplane connector ok. I found the circuit diagram for the CMOS RAM chip in a previous post and checked all the pins. The only thing I haven't done is check power when the machine was on, I will do that.

Be sure you're doing the DEL-startup correctly. Hold DEL. Then power on. Keep it held for a full minute so you can be sure it's passed the '35 second delay' mentioned above.

Full minute? OK, I thought it was 10 seconds. Will try that.

It's also possible (somewhat likely, IME) that the chip itself has died, so you may need to replace it.

I bought a few new ones, since CMOS chips are easy to kill, and put a new one in rather than putting the old one back when I had to remove it to repair the traces to the vias underneath it. Current state is new off-board battery and new CMOS chip.

Also worth checking that you've got the two shunts fitted on the 'GENLOCK' LK6 connector near VIDC - the two toward the rear of the machine should be fitted 1-2 and 3-4. You mentioned that you had a colourcard fitted, so that would have been fitted on this connector originally, so you may have forgotten to put the links back after removing colourcard? These set the video clock (1-2) and the video sync input (3-4).

Ah! I have not replaced anything from removing the colourcard. Thanks.

Is there a guide for what all the links on the A5000 motherboard are/do? I've got the TRM main PCB assembly pdf but no reference for what they are.

Statistics: Posted by pir — Sat May 11, 2024 2:10 am

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