Power on of 664 shows white screen

[opticpow]

Hi All,


Just wondering if anyone has come across a white screen on power up? I'm guessing one of the IC's is sick.


If anyone could point me in the right direction, it would be appreciated.


Wayne.

[Audronic]

@opticpow


A Photo please of the Screen.


Ray

[opticpow]

@opticpow


A Photo please of the Screen.


Ray

Here you go.


Wayne

[Token]

Hi
There's the border, which is nice. Did you tried to press DEL key to get a beep? I think it could be the RAM, maybe some get hot?

[Bryce]

Try reseating the socketed ICs first.

Bryce.

[opticpow]

Hi
There's the border, which is nice. Did you tried to press DEL key to get a beep? I think it could be the RAM, maybe some get hot?

No keys make any sound. None of the chips get hot after about 5 mins.

Try reseating the socketed ICs first.

Bryce.

There are only 3 socketed chips, I removed and reseated them all. Still the same.
I've also attached a pic of the main board for reference. You'll notice that someone has hacked in an ABBA switch. I'm sure that wouldn't be an issue, but you never know. The case has the odd hole in it, so I'm not sure if anything else has been done to it previously. It's an ebayer

[gerald]

The 1st thing I usually check is RAM when I see this kind of screen.
If you have a XMEM or a lower rom board, you can try http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc

[rpalmer]

opticpow,

The attached picture shows some connectors with corrosion, so could it be that some corrosion is elsewhere (particularly around the VGA or RAM) ?

rpalmer

[opticpow]

The 1st thing I usually check is RAM when I see this kind of screen.
If you have a XMEM or a lower rom board, you can try http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc

Hi Gerald,


Thanks for the link.


Can anyone suggest the easiest way to get the ROM onto my X-MEM? I've got an M4 and the X-MEM but I don't seem to be able to have the rom of the X-MEM enabled with the M4 is plugged in on my 6128. I was hoping to upload the test ROM from the M4 filesystem to my X-MEM.


Wayne.

[pelrun]

The M4 already does everything you need. (which is the entire reason you have to disable the XMEM rom function, because the M4 is already doing it.)


Upload the rom into a slot (31 is good) then put that slot number in the lower-rom field at the top of the roms page and check the box to enable it.

[opticpow]

The M4 already does everything you need. (which is the entire reason you have to disable the XMEM rom function, because the M4 is already doing it.)


Upload the rom into a slot (31 is good) then put that slot number in the lower-rom field at the top of the roms page and check the box to enable it.

@pelrun, Of course, hmm target fixation maybe. Thanks


Anyway, as @pelrun suggested, I upload the ramtest to my m4, and booted on my 6128 to test. Works great. Moved over to the target 664, nada. Still white screen, black border. I'm guessing it's more serious than ram??


I've cleaned the contacts with isopropyl alcohol, might try an eraser just in case.


Wayne.

[opticpow]

Ok, an update after liberal use of the eraser.


Bingo, we have a winner!  Now, identifying the particular ram chip??


And a shoutout to @gerald for a cool utility 


Wayne.

[pelrun]

Reading the green/red band from top to bottom gives GGGGGRRG, so bits D1 and D2 are bad. Looking at the schematic that's IC118 and IC119 (http://www.cpcwiki.eu/imgs/2/29/CPC664_Schematic.png right in the very centre.)

[gerald]

As pelrun foud, it's bit 1 and 2. The bits are displayed downward MSB to LSB.

[opticpow]

Reading the green/red band from top to bottom gives GGGGGRRG, so bits D1 and D2 are bad. Looking at the schematic that's IC118 and IC119 (http://www.cpcwiki.eu/imgs/2/29/CPC664_Schematic.png right in the very centre.)

Thanks @pelrun and @gerald. Apologies for the delay, life got in the way 


I've desoldered the offenders, now just sourcing some replacements. http://www.cpcwiki.eu/forum/hardware-related/sourcing-ram-chips


Wayne.

[opticpow]

A Big thanks for @pelrun and @gerald for the help with the diagnosis and to @audronic for the new RAM chips, the 664 is alive.
[attach=2]
[attach=3]


Now on to the keyboard and drive.


Thanks,


Wayne.