Macintosh IIci - No chime or video after recapping. Any ideas?

[Mac84]

Hello all,

I'm working on a particularly unhappy Macintosh IIci board. After a recap and repair of the startup circuit area, the system turns on (with a green LED on the board), but I don't get a chime. The speaker does "pop". I'm using known-good RAM and the PSU is good as well.

When I turn the system on I get a blank screen, but I do get a colorful (often pink or yellow) flash on the screen once I press the Reset switch on the board.

Oddly enough, the system acts the same whether RAM is installed or not!

Sadly, the bottom of the board (see attached photos) has a LOT going on, although most of the traces appear to map out okay, I'm sure there could be a problem.... somewhere...!

Here's what I've tried:
- Using a ROM SIMM to bypass the built in ROM
- Swapped the three chips by the startup circuit with new chips
- Looking at the board with a thermal camera (nothing stands out)
- Reflowing the ROM pins under the board
- Reflowing the PSU connector under the board
- Cleaning up around the sound chip
- Cleaning up around the startup circuitry
- An ultrasonic bath

Any ideas of chips / areas to pin out or further troubleshooting paths would be great, thanks!

-Steve

 

[Kai Robinson]

Hello all,

I'm working on a particularly unhappy Macintosh IIci board. After a recap and repair of the startup circuit area, the system turns on (with a green LED on the board), but I don't get a chime. The speaker does "pop". I'm using known-good RAM and the PSU is good as well.

When I turn the system on I get a blank screen, but I do get a colorful (often pink or yellow) flash on the screen once I press the Reset switch on the board.

Oddly enough, the system acts the same whether RAM is installed or not!

Sadly, the bottom of the board (see attached photos) has a LOT going on, although most of the traces appear to map out okay, I'm sure there could be a problem.... somewhere...!

Here's what I've tried:
- Using a ROM SIMM to bypass the built in ROM
- Swapped the three chips by the startup circuit with new chips
- Looking at the board with a thermal camera (nothing stands out)
- Reflowing the ROM pins under the board
- Reflowing the PSU connector under the board
- Cleaning up around the sound chip
- Cleaning up around the startup circuitry
- An ultrasonic bath

Any ideas of chips / areas to pin out or further troubleshooting paths would be great, thanks!

-Steve

How hot do the SCSI and SWIM chips get with power on?

 

[Mac84]

How hot do the SCSI and SWIM chips get with power on?

The only chip that got hot (126 F) was UC4 (behind the serial ports). And seeing as the other working IIci is happy without it, I removed it from the problematic system. However that didn’t seem to make much of a change.

It seems the color / pattern I see when pressing the reset button changed without the chip, but it also seems to change randomly.

The attached photos are before / after removal.

 

[Kai Robinson]

Yah - UC4 is one of the 26LS30's - not vital unless you need that serial port. Have you got a spare ADB chip (UA13) or RTC Chip (UK14)? You can grab these off a dead Classic board if needed. I'd be interested to know if you replaced Q2, or measure what voltage it outputs when you apply power to the board.

Check the bus transcievers at UD6, UD7, UJ8 and UJ9 (the 74F245's), check the connections at the MDU (UK11) and check for the bus clocks being present.

That should be enough to go on with for now

 

[Mac84]

Yah - UC4 is one of the 26LS30's - not vital unless you need that serial port. Have you got a spare ADB chip (UA13) or RTC Chip (UK14)? You can grab these off a dead Classic board if needed. I'd be interested to know if you replaced Q2, or measure what voltage it outputs when you apply power to the board.

Check the bus transcievers at UD6, UD7, UJ8 and UJ9 (the 74F245's), check the connections at the MDU (UK11) and check for the bus clocks being present.

That should be enough to go on with for now

Thanks Kai!

Q2 gives me -11.8 V on the middle pin and -5 V on the right pin. This is appears to be the same on the working IIci. I will however check on everything else you suggested too, thanks!

Update: Swapping the RTC didn't change anything. Swapping the ADB chip didn't change much, the only difference is now when I press the Reset button, the pattern is a solid color, not distorted like it used to be. But I'll continue!

Can you describe a way to check the clock on (I assume you meant UJ6/7 + UJ8/9) without an oscilloscope ?

 

[Garrett]

Hi Steve, I'm fighting almost the same problem: https://tinkerdifferent.com/threads/another-iici-thread-no-video.2730/

I'll let you know if I solve anything on my end. My board does chime, but all other symptoms you mentioned are happening with this one as well.

 

[Willj]

Thanks Kai!

Q2 gives me -11.8 V on the middle pin and -5 V on the right pin. This is appears to be the same on the working IIci. I will however check on everything else you suggested too, thanks!

Update: Swapping the RTC didn't change anything. Swapping the ADB chip didn't change much, the only difference is now when I press the Reset button, the pattern is a solid color, not distorted like it used to be. But I'll continue!

Can you describe a way to check the clock on (I assume you meant UJ6/7 + UJ8/9) without an oscilloscope ?

Steve, did you ever get this issue solved as I have a board doing the same thing???

 

[Mac84]

Sadly no, due to the horrible condition of the bottom of the board, I simply assume there is some trace not connecting somewhere.