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IIcx not booting (no chime, partial video)


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Hello,

 

History:

Trying to repair a IIcx. I got it from a basement for a cheap price. Unfortunately it didn't even boot at first. The PSU is dead.

Tried with a known good PSU, and it wasn't better. After a full recap, the board was powering on.

 

There is no chime, but it will boot sometimes with a half broken screen. Sometimes it will even display the floppy disk icon.

 

2%20-%20bad%20checkerboard.jpg

 

Tests: 

Tried swapping the CPU (socketed IIcx…): no change 

Tried whitout RAM: no change

Tried IIx ROM: no change

Tried another Toby card: no change (well the broken part on the screen is slightly different)

Tried Rominator II: It make a continuous high pitched noise, like it was trying to play some chime but ended stuck on one sample. Looking with a Logic Analyser, this seems likely:

 

2%20-%20ROMinator%20II%20bad%20start.png

 

Missing components:

The "bad" board do not have D1 and D2 near the sound chips. My working Iicx has them. Can someone on a working IIcx check if D1 and D2 are present ?

 

2%20-%20sound%20chip%20missing%20D1%20D2

 

My working IIcx has them:

 

1%20-%20sound%20chip%20installed%20D1%20

 

Guesses:

I'm guessing something is broken on address/data lines. Looking with a Logic Analyser didn't show anything useful. 

 

Anyone have an idea what to try next ?

 

Regards

Edited by demik
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Watching with interest. I recapped two IIcx boards recently. One works great, the other on the power button (keyboard or back of machine) starts up the power supply fan, no chime, no video. Pushing the power button on the back shuts down the machine again...

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I have two working IIcx systems, neither have D1 or D2 populated.

 

Suspecting something amiss around the area of UM2, UL2,UK2, and the F258s above those possibly?

 

 

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On 4/27/2021 at 1:09 AM, ScutBoy said:

Watching with interest. I recapped two IIcx boards recently. One works great, the other on the power button (keyboard or back of machine) starts up the power supply fan, no chime, no video. Pushing the power button on the back shuts down the machine again...

 

Thats what I got as well. I'm thinking either a component issue or a rotten via somewhere. Think is this board is clean and had little goo from capactitors

 

On 4/27/2021 at 2:07 AM, Daniël Oosterhuis said:

My IIcx, which is currently functional, does not have D1 and D2.

 

On 4/27/2021 at 2:57 AM, joshc said:

I have two working IIcx systems, neither have D1 or D2 populated.

 

Suspecting something amiss around the area of UM2, UL2,UK2, and the F258s above those possibly?

 

Thanks for confirming this. Looking at schematics, D1 and D2 are flyback diodes and are indeed not strictly needed. I will get a couple of F258s to test.

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I will lift both sound chips, clean underneath and solder back again. 

 

Sound chips are used in the boot sequence, and from the picture, legs are looking dull or contaminated. 

 

Had as one issue related to that problem. 

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Thanks for the feedback. I will try what you guys suggested. I will need to buy sockets for the sound chips, as I don't like putting thoses without a socket.

 

Meanwhile I'm going to look for broken traces

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20 hours ago, demik said:

I will need to buy sockets for the sound chips, as I don't like putting thoses without a socket.

 

Buy good quality sockets, the cheap ones you can get from eBay or AliExpress suck. They make very poor contact, and will have you ripping your hair out figuring out why things are very intermittent. Speaking from experience here!

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20 hours ago, Daniël Oosterhuis said:

 

Buy good quality sockets, the cheap ones you can get from eBay or AliExpress suck. They make very poor contact, and will have you ripping your hair out figuring out why things are very intermittent. Speaking from experience here!

 

Thats my experience as well. I get my sockets from Mouser or Conrad

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