CPC-464 freezes on start-up with black background colour

Started by Tezz, 14:48, 04 March 24

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Tezz

Quote from: McArti0 on 16:36, 11 April 24Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.
Ok, thanks. I'll try that too.

These SN74LS32 are listed on eBay, 10 for just over a fiver. Photo seems to show the correct SN74LS32N but can you confirm these are correct for me to order.

https://www.ebay.co.uk/itm/166211136961

Thanks again to all!


McArti0

CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz

I've now removed IC112 from the board and installed a socket. The new SN74LS32N are on the way.

I wanted to test this logic IC in my TL866II but the latest version of xgpro seems to have removed all the 74 logic from the list. Is there something I'm missing with this latest version in order to test it?

Rabs

Select Tools then Logic Test and 7432 but this is with version 11.9

You cannot view this attachment.

Tezz

Quote from: Rabs on 14:50, 12 April 24Select Tools then Logic Test and 7432 but this is with version 11.9

You cannot view this attachment.
Ah, thanks for the info, I did see 7432 listed but wasn't entirely sure it was actually 74LS32 as they were specifically listed in previous versions 

Tezz

Test seems to pass with the same result as your screenshot 

McArti0

Mayby not work on hi freq. Try now connect 4,5 pin to z80 pin 20,21.
CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz

The 7432s arrived this morning but no change with the new one installed unfortunately. 

McArti0

Quote from: McArti0 on 16:36, 11 April 24Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.
You can instead search for busrq Just take out the Z80.
CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz

Quote from: McArti0 on 12:00, 15 April 24
Quote from: McArti0 on 16:36, 11 April 24Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.
You can instead search for busrq Just take out the Z80.
Ok, will check this out next, thanks.

Tezz

Quote from: McArti0 on 16:36, 11 April 24Last test ic112 before desolder.
Pin 37 expansion port BUSRQ to ground, pin 4,5 ic112 to ground and You should have 0V on Pin6 but you have not.

Pin 37 expansion port BUSRQ to ground, pin 1,2 ic112 to ground and You should have 0V on Pin3 and you have.
Ok made some time today to do this...

Pin 37 expansion to ground, pin 4&5 of IC112 to ground, pin 6 reads 0v

Pin 37 expansion to ground, pin 1&2 of IC112 to ground, pin 3 reads 3.6v

McArti0

Quote from: Tezz on 18:52, 16 April 24Pin 37 expansion to ground, pin 1&2 of IC112 to ground, pin 3 reads 3.6v
this is proof that ic112 has a defect. but the computer shows that this track is working properly, so you probably shorted pins 1,2 to ground incorrectly.
CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz

Quote from: McArti0 on 19:03, 16 April 24
Quote from: Tezz on 18:52, 16 April 24Pin 37 expansion to ground, pin 1&2 of IC112 to ground, pin 3 reads 3.6v
this is proof that ic112 has a defect. but the computer shows that this track is working properly, so you probably shorted pins 1,2 to ground incorrectly.
Hi, I double checked that pins 1&2 were shorted to ground. I used one wire across pins 1&2 to ground

McArti0

Ok. Now Insert ROM diag, and when CPC freeze You connect new Diode, catode to Pin 6 ic112, anode to Z80 WAIT line (or READY on exp port) this connect must be strong and const.
This halted Code on Read 8255 PB instruction. You can check input voltage on D0-D7 line. D0 should be 0 , D1-7 ~5V.

But have You diode?
CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

McArti0

CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz


Tezz

Quote from: McArti0 on 19:48, 16 April 240+0=0 you cant have 3,6V on Pn3
I'll repeat the test again in the morning

McArti0

CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz

Quote from: McArti0 on 22:08, 18 April 24test input 8255
Thanks, I will certainly do this.

I didn't get free time yesterday to progress with testing but I intend to look more into the PIO.

Tezz

I've been busy the past couple of weeks so I'm just getting back onto this. I'm considering swapping the PIO. Is this a suitable replacement? https://www.ebay.co.uk/itm/225089493089

McArti0

@Tezz 
"I'm considering swapping the PIO"

But did he pass or fail the test?
CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz

After a long break due to lack of free time, I've continued today. I removed the 8255 PIO and swapped it out with a known working one taken from a spare long board and there was no change with the fault. Perhaps there's a trace fault somewhere with the board after all my previous reworking although I did do continuity checks with the board for some time previously without finding issue. I'm pretty stumped after swapping out almost all the ICs

McArti0

Insert original ROM.
short LK1 and reset. When reset, name on screen Orion
short LK2 and reset. When reset, name on screen Schneider
short LK3 and reset. When reset, name on screen Solavox

https://www.cpcwiki.eu/index.php/LK-selectable_Brand_Names

this will confirm that 8255 is being read.

CPC 6128, Whole 6128 and Only 6128, with .....
NewPAL v3 for use all 128kB RAM by CRTC as VRAM
TYPICAL :) TV Funai 22FL532/10 with VGA-RGB-in.

Tezz

Quote from: McArti0 on 19:47, 25 August 24Insert original ROM.
short LK1 and reset. When reset, name on screen Orion
short LK2 and reset. When reset, name on screen Schneider
short LK3 and reset. When reset, name on screen Solavox

https://www.cpcwiki.eu/index.php/LK-selectable_Brand_Names

this will confirm that 8255 is being read.


Thanks, I'll check that out next. We're having some building work done this week so everything is packed away for the next week or two.

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