Issue 6 ELK - White Screen

[bagpuss22]

Gents,

I have a lovely Issue 6 with the standard white screen.

I have replaced the TM4164EC module but to no avail

I assume that the issue could now be the ULA, soldered in blob!?

Any thoughts on other things to check or where I could find a replacement ULA?

Cheers

Russ

[stuslayer]

Dave Hitchins would probably be a good source of info, it's my (limited) understanding that it's rare for Issue 6 ULA's to go bad, but more knowledgeable people will give you a more definitive answer.

[danielj]

It's more likely to be the processor or the ROM than the ULA I'd have thought in this instance. Do you have any way of checking signals?

d.

[CMcDougall]

weird, usually always the 4x 8k ram
Was in mine , after checking 6502 & 32k rom

[bagpuss22]

HI all,

No access to other kit apart from a DVM which will do frequency....

The RAM is a single TM4164EC and I have replaced that with a new one.

Can ROM or CPU cause a white screen?

[CMcDougall]

the 32k rom can, as that's how I fixed my cousin's one BITD

not had a faulty 6502, but someone recently posted a thread, & found it was that, so can do too

[bagpuss22]

I am hoping it's not the ULA as I probably cannot source one.

As for 6502 then I have a few and ROMs can be replaced.

OK where to start really.....

[daveejhitchins]

I am hoping it's not the ULA as I probably cannot source one.

As for 6502 then I have a few and ROMs can be replaced.

OK where to start really.....

I've only ever seen 1 issue 6 ULA failure, but that doesn't mean there can't be others! Definitely try the ROM and processor first. I also recomend going through the service manual fault finding guide as well.

Unfortunately, until the UEU is ready (or just a FPGA replacement) I won't have any ULAs spare

Good luck. Keep us updated on your progress . . .

Dave H

[bagpuss22]

OK, I have now socketed the ROM and CPU.

Read the ROM content out and compared it to the ROM files and all looks OK.

WIth the original CPU in, with no keyboard connected: FULL WHITE SCREEN.
with keyboard connected: FULL WHITE SCREEN, LED lit or
WHITE HORIZONTAL bars, LED not Lit.

With new R65C02P3 in, with no keyboard connected: WHITE HORIZONTAL bars briefly then black screen, sometimes with a few flashing pixels.
with keyboard connected: WHITE HORIZONTAL bars briefly then black screen, sometimes with a few flashing pixels. LED lit

PS the Pixels are the same each time...

[Kazzie]

Hm, ROM RAM and CPU swapped out... have you checked the clock and reset signals for the CPU?

[bagpuss22]

Think that is my next port of call..........