8-bit acorn hardware • Re: IC88, IC100 and the Tube issues

I've been busy resolving a few underlying hardware issues on the Beeb ...

• The 74LS245 at IC14 was failing and pulling down the data lines, so replaced that.
• One of the leads for R13 had broken at the board, but was somehow still making contact ... sometimes.
• The ROM sockets were hopeless so replaced them. While I was at it, all the "large" chips (24 pins or more) were in the same rubbish sockets, so replaced them all.

Now the Beeb is running great - has been running a BASIC memory test program every day for the past week for hours on end with no problems. Unfortunately that hasn't made any difference to my copro issues - still crashes in exactly the same way in either the Z80 monitor or CP/M. Just to confirm (as this has been going on for a while), the copro seemed to work fine when tested on another Beeb, and my Beeb is now completely stable without the copro.

I have nabbed my son's oscilloscope and have started poking around, but am afraid that I am chasing shadows. Could someone point me to a more methodical approach to hunting down my Tube-specific issue? I have had a look through the fault finding thread, but can't find any similar issues.

Cheers,

Ian.

Statistics: Posted by simmo1010 — Mon Mar 04, 2024 11:31 am

---