General Stuff(tm)

[Tomswork]

Just a note I have found that resistor packs can cause thus problem when the individual values vary on the pack


Tom

[stephen_usher]

OH. OK.

I'm not spraying anywhere near them at the moment but I'll keep it in mind.

[stephen_usher]

Replaced one of the RAM which seemed sensitive to heat but it made no difference and the chip passed the RAM tester.

I may pull the rest of that bank tomorrow, fit sockets and change out the RAM chips. At least that should eliminate those as the potential fault.

[stephen_usher]

Working from home again today and it's pretty quiet leading up to Christmas so had a chance to carefully freeze the tops only of chips.

No change other than if I freeze MA6 RAM chip and then the errors start building up, so I'm guessing that it may be that one and it's feeding stuff down the address lines or something.

I may get time later to swap it out.

[stephen_usher]

Swapping out MA6 solved the problem.

The original chip passes my RAM tester tests but fails in the system.

So, there's another strange failure mode for DRAMs... outputting voltages onto the address bus.

Of course, this means that I have one fewer spare 41256 chip, so I don't have quite enough to upgrade the machine to 1MB. Oh well.

[rubber_jonnie]

Swapping out MA6 solved the problem.

:dualthumbup:

:girldance: :girldance: :girldance:

[stephen_usher]

@rubber_jonnie I think my Apricot FP has been talking to your Mac. The keyboard/mouse interface has just stopped working.

Data's being received by the optic board but isn't being read by the Z80 SIO for some reason. *sigh*

[rubber_jonnie]

Oh no!

[stephen_usher]

There's not much there, a 556 and a 74LS74. It can't be the SIO as the reset isn't working too, which is before the SIO using separate circuitry.

FP-Keyboard-IO.jpg

[Tomswork]

Is tr1 operating properly?


Tom