Any IICX chip level repair experts? I've got a clock but RESET / ARST is stuck high

[Sideburn]

Hello all who might be interested in this sort of thing,

I finished going over this pretty bad board, I fixed all the broken traces I have found so far and re-capped the board.
I finally got the power button to kick the power supply on so the power circuit is now working.
I rigged a bench supply now to do some deeper level troubleshooting and O'scoped around for a clock.
I am getting a good clock through out and to the 68030 but RESET is stuck high and I am not sure how to figure out what is pulling it high since there's ARST in many places on the board.

I have all of the simms out right now and im just trying to get to a power chime level or see some signals on the address and data lines.

Could the SWIM chip or the sound area be pulling RESET high?

Anyone have any suggestions on where to go next?

Thanks,.

-Tavis

 

[Kai Robinson]

Check the Sony SND chip for what it's doing with the /RESET line

 

[Sideburn]

Oh wow ok I was wondering. That’s where all the horrible corrosion is and I’ve had to patch a bunch of traces

 

[Sideburn]

Check the Sony SND chip for what it's doing with the /RESET line

Finally revisiting this.. Which chick are you referring to exactly. I see no Sony chips they are all apple branded. Do you mean the Left and Right audio chips at UA15 and UB15 ? or do you mean UD14?

 

[Kai Robinson]

Finally revisiting this.. Which chick are you referring to exactly. I see no Sony chips they are all apple branded. Do you mean the Left and Right audio chips at UA15 and UB15 ? or do you mean UD14?

UA15 and UB15 are the 20-pin PLCC 'SND' Chips (left and right channel) - Apple P/N 343S0045-B (Made by Sony though). It's the one actually responsible for sound output, but also functions as /RESET (or /RST) for the CPU.

Pin 6 is the active low reset signals, with UB15 being responsible for /ARST and UA15 being responsible for /BRST

Chips that use /ARST = ADB (UL6) / SWIM (UL14) / ASC (UD14) / VIA1 (UK6) / VIA2 (UH6) / SCSI (UJ15) / 68030 CPU (UK10) / 68882 FPU (UC8) / NUCHIP (UG8)
Chips that use /BRST = GLUECHIP (UK13)

So - if /BRST is being generated OK, and doing it's thing, then /ARST is the signal to check for. If it's being generated OK - check each of the chips it's connected to in the schematic, at the relevant pin, to make sure that chip is receiving the /ARST signal.

You may find the BOMARC Schematics attached, useful:

 

[Sideburn]

UA15 and UB15 are the 20-pin PLCC 'SND' Chips (left and right channel) - Apple P/N 343S0045-B (Made by Sony though). It's the one actually responsible for sound output, but also functions as /RESET (or /RST) for the CPU.

Pin 6 is the active low reset signals, with UB15 being responsible for /ARST and UA15 being responsible for /BRST

Chips that use /ARST = ADB (UL6) / SWIM (UL14) / ASC (UD14) / VIA1 (UK6) / VIA2 (UH6) / SCSI (UJ15) / 68030 CPU (UK10) / 68882 FPU (UC8) / NUCHIP (UG8)
Chips that use /BRST = GLUECHIP (UK13)

So - if /BRST is being generated OK, and doing it's thing, then /ARST is the signal to check for. If it's being generated OK - check each of the chips it's connected to in the schematic, at the relevant pin, to make sure that chip is receiving the /ARST signal.

You may find the BOMARC Schematics attached, useful:

Thanks, yes ive been pouring over the schematic. ARST is high.. I have a clock and thats about it. I fixed a bunch of broken traces so far and have re-capped the whole board. I thought ARST is active hight (since there's a line over the top) when its high the 68030 will be in reset correct?

I have pulled both UB15 and UA15 off the board thinking that will rule them out, correct? So this means something else is pulling reset high?

Or do I have this all wrong? lol

Thanks for helping. Would love to solve this one. It's a tough one because the board is in pretty bad shape, lots of corroded broken traces. But it seems like there's hope. It wouldn't even power on at first but I got the power circuitry working and the LED is turning on when you push the power button and I can see clock signals all over the board. just no address and data and no power chime (especially now that ive pulled the two sound chips)...

I've got the sims removed and no battery but this shouldn't matter in order to get the board running, right?

 

[Kai Robinson]

Line over means active low

 

[Sideburn]

Line over means active low

I realized that lol I made the mistake of trusting ChatGPT out of laziness instead of confirming. From 68030 reference.

it’s seems to vary sometimes no?
Anyway, now that I know it’s not RESET, I need to figure out what the key areas are to check with the scope. Im getting nothing front he address and data lines off the 030.

I have a logic analyzer as well but I only know enough to get me in trouble and waste a lot of time

 

[Kai Robinson]

Have you checked for the presence of the clock signals at the cpu, gluechip, mdu, rbv, oscillator output and also the E clock?

 

[Sideburn]

Have you checked for the presence of the clock signals at the cpu, gluechip, mdu, rbv, oscillator output and also the E clock?

yeah, I checked the oscillators Y1, Y2, Y3,
And Y4 and click on the 68030, 6882, UF11,
UG11 and UG13. I will check the gluechip. Not sure what the mdu, rbv, and e clock are.

Been hunting down and patching broken traces as well. I found a couple more by the scsi chip and external scsi port but I don’t think they would be causing the lack of data and address signals.

 

[Kai Robinson]

Ah sorry you wont have the MDU or RBV, i was thinking of the IIci there - the E clock is the fixed 783KHz clock used for peripheral timing. It's the bus clock speed divided by 10, typically. So it may be 1.56672MHz.

 

[Sideburn]

OK Here are my new findings:

For starters I have no oscillation on Y4 or at Um5 pin 2 and 3 as well. they are sitting at 2.4v

Not sure if this is important or not. Is this just the realtime clock or is it part of the VIA chips and are they required to get the MPU running?

On the MPU:

Reset, halt, ds, as, r/w all go high on power up
I have a 16mhz clock at E1 on the 68030.
Data lines are sitting at 1.5v
Address lines are low

UG11 has both 30 and 40mhz clocks

Uf11 pin 5 has 16mhz clock

FPU clock is also good

Glue chip pin 17 has a 30mhz clock and pin 18 has a 16mhz clock.

Pin 72 has a 782khz via clock

Y1 is 16mhz

Y4 dead

Any suggestions where to go next?

 

[Kai Robinson]

Y4 should be a simple 2 pin 32.768KHz crystal (not an oscillator), if you're not getting anything from that at all when power is applied, that means the RTC won't be running, and won't be generating the 1second pulse output, or sending any data to the VIA. Although that may not have too much of an effect on the system as a whole.

 

[Sideburn]

Y4 should be a simple 2 pin 32.768KHz crystal (not an oscillator), if you're not getting anything from that at all when power is applied, that means the RTC won't be running, and won't be generating the 1second pulse output, or sending any data to the VIA. Although that may not have too much of an effect on the system as a whole.

Right. I figured it wouldn’t affect the system as a whole. I ordered some crystals. I know it’s a resonator and not an oscillator. The ones I ordered call them both but I’m pretty sure it’s just a crystal. There was a broken trace but after I fixed it it still wasn’t oscillating. This is what I ordered: uxcell DIP Quartz Crystal Oscillators Resonators 32.768KHz Replacements 2 X 6mm 10 Pcs https://a.co/d/eI6oi62

 

[Sideburn]

I don’t need to have the memory sims installed either in order for the system to run correct?

 

[Kai Robinson]

I don’t need to have the memory sims installed either in order for the system to run correct?

You do need a minimum of 1MB (in Bank A) for anything to really happen, as the built in video needs something to use.

 

[Sideburn]

You do need a minimum of 1MB (in Bank A) for anything to really happen, as the built in video needs something to use.

I don’t even have a display or anything hooked up. Not even a speaker. I’m only trying to get anything other than a clock right now. Some square waves off the roms mpu etc. For that I shouldn’t need any RAM installed right?

 

[Sideburn]

Hey Kai I have been watching the livestream on YouTube you were in on mac84s channel and my iicx had the exact same issue. I have clocks and reset but no activity. You mentioned removing a jumper somewhere and walking the bus. I’d like to try that but I don’t know what jumper.
Also what docs are you looking at in addition to the schematics? They have seem like they have some good info.