Anyone up for some IIcx troubleshooting assistance? We have clocks but no activity...

[Phipli]

/CE? On the ROM.

Erm... I'd say Reset and clock on the cpu, but they're not as easy to clip onto.

 

[Sideburn]

Well I got back to it today. I now have the other board and i Re-capped it today. It is a much cleaner board but there were a few visible broken traces I had to fix. Anyway, after cleaning and re-capping, the board makes the sad mac sound on power up. But at least this board is booting and I can see square wavs on the ROMS.

I tried connecting a video card up to a monitor but there nothing.

When I probe the pins on the NUBUS I see nothing. When I probe the lower pins of UD and UCI have signals but none on the upper pins of the chips.
Another issue I see is when i connect the actual IICX power supply, after a short delay the power supply just turns itself on and the green LED on the board lights but the rest of the board is not powering up and the soft power button does nothing. So there is also something wrong with the power circuit. Not sure if they are related though...

So, since this board is in "better" shape I guess I will focus on repairing it first now.

Anyone have any ideas on what chips to look at?

 

[Phipli]

Well I got back to it today. I now have the other board and i Re-capped it today. It is a much cleaner board but there were a few visible broken traces I had to fix. Anyway, after cleaning and re-capping, the board makes the sad mac sound on power up. But at least this board is booting and I can see square wavs on the ROMS.

I tried connecting a video card up to a monitor but there nothing.

When I probe the pins on the NUBUS I see nothing. When I probe the lower pins of UD and UCI have signals but none on the upper pins of the chips.
Another issue I see is when i connect the actual IICX power supply, after a short delay the power supply just turns itself on and the green LED on the board lights but the rest of the board is not powering up and the soft power button does nothing. So there is also something wrong with the power circuit. Not sure if they are related though...

So, since this board is in "better" shape I guess I will focus on repairing it first now.

Anyone have any ideas on what chips to look at?

What RAM setup did you have?

What video card?

What video adapter? What monitor?

 

[Sideburn]

I loaded all of the banks of ram but I’m not sure what the minimal requirement is.

The video card is radius 24 bit.

Apple high res monitor.

I just noticed D1 and D2 are strangely missing from the board!

Looks like D2 is in the soft power circuit and D1 is part of the ports circuit.

Not sure what value they are and the ones on the original board are not looking so good.

 

[GRudolf94]

I wouldn't use that as a test video card. Got anything lousier?

Standby for more ideas when I get to my computer

 

[Sideburn]

Well I transplanted those two diodes and it made no difference.

Stock PSU turns itself on in low power more (the fan barely spins) and only the led on board turns on.

Original board power circuit still works properly without the diodes.

Anyway main issue is the sad Mac chime when powering up off the bench atx supply.

I see no activity on the NUBUS

 

[Sideburn]

I wouldn't use that as a test video card. Got anything lousier?

Standby for more ideas when I get to my computer

Unfortunately that’s all I’ve got.

 

[Sideburn]

I do have a vga adapter and a modern LCD display though. But I think in need some NUBUs activity before anything. I put a scope on all the pins on the video connector and nothing.

 

[Phipli]

I loaded all of the banks of ram but I’m not sure what the minimal requirement is.

Are they all the same SIMMs?

I just noticed D1 and D2 are strangely missing from the board!

Thats normal remove the ones you added. Google pictures of the board.

Anyway main issue is the sad Mac chime when powering up off the bench atx supply.

Video out is the important thing. If you get video working you can see an error code.

 

[Sideburn]

Are they all the same SIMMs?

Thats normal remove the ones you added. Google pictures of the board.

Video out is the important thing. If you get video working you can see an error code.

Yes all the same ram chips.
Right video out. But no Nubus = no video.
And it is odd that the soft power circuit isn’t working.
Maybe need to rule out my atx power supply and or fix the power up circuit.

 

[GRudolf94]

Basic steps of troubleshooting are always voltages, clocks, reset.

However, if you look at the schematics, D1 and D2 both directly affect the power-on circuitry. They weren't there, why add them?

 

[Phipli]

But no Nubus = no video.

Then Nubus first

 

[Sideburn]

Basic steps of troubleshooting are always voltages, clocks, reset.

However, if you look at the schematics, D1 and D2 both directly affect the power-on circuitry. They weren't there, why add them?

The original bad board we were working on has them. So I swapped and neither board behaved differently.

 

[GRudolf94]

Ok, but boards undergo revisions. You shouldn't assume things about component placement.

 

[Sideburn]

Since my original bad board that I’ve owned since new has then and the new board I got that is the exact same version number does not have them I thought someone might have removed them.

 

[Sideburn]

Ok, but boards undergo revisions. You shouldn't assume things about component placement.

The board revs are identical.

 

[GRudolf94]

The PCBs are. The BoM, not necessarily.

 

[Phipli]

Since my original bad board that I’ve owned since new has then and the new board I got that is the exact same version number does not have them I thought someone might have removed them.

The solder on the pads looked factory, there is likely two variants.

 

[Phipli]

This could be a parts availability thing - its smart to design options into your board.

An example is the LC 475 - there are three different RAMDACs fitted to different boards, two have a function integrated into the RAMDAC and the third requires an extra chip.

Adding that missing chip to a board that didn't have it... wouldn't be good.

 

[GRudolf94]

Same section of the IIcx board as shown by recap-a-mac. Also 0230-B.




Anyway, this all is besides the point. Throwing random parts at it, especially ones taken from an equally defective board, is not the way to go.