CPC6128 boot issue

Bryce · 15:15, 23 July 23

My guess is that one of the 74LS153's has a stuck bit on one of the CRTC outputs.

Bryce.

eto · 15:43, 23 July 23

Quote from: Bryce on 15:15, 23 July 23My guess is that one of the 74LS153's has a stuck bit on one of the CRTC outputs.

Bryce.

wouldn't that also have the effect that the in the area of text there should be vertical stripes too?

deano467 · 16:51, 23 July 23

Quote from: Bryce on 15:15, 23 July 23My guess is that one of the 74LS153's has a stuck bit on one of the CRTC outputs.

Bryce.

Hi Bryce, those 4 chips are cheap to swap out. Do you think the piggyback technique would work here to find any which are faulty? Thanks

Bryce · 19:20, 23 July 23

Quote from: deano467 on 16:51, 23 July 23
Quote from: Bryce on 15:15, 23 July 23My guess is that one of the 74LS153's has a stuck bit on one of the CRTC outputs.

Bryce.
Hi Bryce, those 4 chips are cheap to swap out. Do you think the piggyback technique would work here to find any which are faulty? Thanks

I'm not a fan of the piggyback technique in general, but as well as that, the technique will never work with a stuck bit. It will just cause a short and damage the chip you stuck on top.

But yes, you're right, it would most likely cause stripes through the text too. Have you tried changing the background and text colours in basic to see what the effect/error looks like then?

Bryce.

deano467 · 19:35, 23 July 23

Bryce, only once was I able to get it to go to ready screen, but when I pressed keys only garbage was displayed. also managed to hear some beeps through the speaker when I pressed some keys.
There is no chance to change colours unfortunately

deano467 · 13:25, 31 July 23

I purchased the dandanator and it has determined a faulty ram chip. It also loads up other games somewhat, so I am hoping that is all that is wrong here.

Rabs · 16:40, 31 July 23

Quote from: deano467 on 13:25, 31 July 23I purchased the dandanator and it has determined a faulty ram chip. It also loads up other games somewhat, so I am hoping that is all that is wrong here.

Sounds promising but odd. Don't understand how anything works if one RAM IC (i.e. 1 bit on all bytes) is failing, unless it is some odd sort of failure mode.

Rabs · 17:25, 31 July 23

Does the upper RAM bank test pass?

deano467 · 18:44, 31 July 23

Quote from: Rabs on 17:25, 31 July 23Does the upper RAM bank test pass?

The games boot up with graphical glitches. That's as far as dandanator tests. I need to replace the faulty lower ram chip first to get it to boot further to test the upper ram

Rabs · 18:56, 31 July 23

You can swap the banks. Forcing 2nd RAM bank. I have never done it though.

deano467 · 11:12, 09 August 23

Hi again. Just to feedback I replaced IC130 ram and I am now greeted with the correct boot screen

.
All lower and upper ram tests now pass.

However using the dandanator it fails on the ROM test. Anybody have any ideas as the computer seems to be working well otherwise, loads games etc.

Also doing a prolonged soak test and no issues detected.

Rabs · 12:21, 09 August 23

Quote from: deano467 on 11:12, 09 August 23Hi again. Just to feedback I replaced IC130 ram and I am now greeted with the correct boot screen .
All lower and upper ram tests now pass.

However using the dandanator it fails on the ROM test. Anybody have any ideas as the computer seems to be working well otherwise, loads games etc.

Also doing a prolonged soak test and no issues detected.

That's good. No idea why the Diagnostic upper ROM is showing as failed.

eto · 20:11, 09 August 23

I also get an Upper Rom failed on my 6128s. Maybe there are variations of AMSDOS that have a different checksum.

Rabs · 20:36, 09 August 23

Quote from: eto on 20:11, 09 August 23I also get an Upper Rom failed on my 6128s. Maybe there are variations of AMSDOS that have a different checksum.

Same checksum as mine and mine passes. There is an issue posted on github about this I think.

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CPC6128 boot issue