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

[Sideburn]

Hey all,

I've posted this in tinkerdifferent as well but have only got one person to help out some so trying over here...

Ive been troubleshooting my old super corroded Mac Iicx.. so far ive managed to get the power circuit working so pressing the power button fires up the power supply and the board is receiving power. The LED is lighting and I have all the correct oscillator and clock frequencies that I have seen so far.

Other than that the board is dead. I have pulled the sims off the board for now while just truing to see some square waves across there address and data lines.

What I have seen so far:


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

I am stuck now trying to figure out what to check next to see why theres no activity on the 68030.

Any suggestions would be great.

** The board has been re-capped, scraped, cleaned and all broken traces I have found so far have been fixed.

Thanks,

-Tavis

 

[Phipli]

Do you have photos? Whats it like around and under the battery holder?

What is the reset line doing?

Does the CPU get warm?

 

[Sideburn]

Do you have photos? Whats it like around and under the battery holder?

under the battery looks ok.
under the power switch was bad and i fixed broken traces.
Photos attached

What is the reset line doing?

I mentioned above-- Reset, halt, ds, as, r/w all go high on power up... they are all active low...

Does the CPU get warm?

No I put a thermal camera on it and nothing is warm.

 

[Sideburn]

I have removed the two sony sound chips for now
attached are pics of the broken traces I have fixed so far

 

[Phipli]

I mentioned above-- Reset, halt, ds, as, r/w all go high on power up... they are all active low...

Sorry, missed reset in the list.

They don't go low for a period of time? What if you manually press the reset button, front left of the board?

I have removed the two sony sound chips for now
attached are pics of the broken traces I have fixed so far

Erm... aren't the sound chips part of the reset circuit? I forget this machine's specifics.

 

[Phipli]

attached are pics of the broken traces I have fixed so far

Are those vias functional? They look nasty.

 

[Phipli]

@Sideburn :

 

[Sideburn]

Sorry, missed reset in the list.

They don't go low for a period of time? What if you manually press the reset button, front left of the board?

I tried that yesterday.. button does nothing and they never go low.

Erm... aren't the sound chips part of the reset circuit? I forget this machine's specifics.

Yes at first I was being stupid and i thought reset was active high, so i pulled those sound chips thinking they might be pulling reset high.
but reset is active low and its never going low..

 

[Sideburn]

Are those vias functional? They look nasty.

I continuity checked all around there and they are good.

Yeah this is a challenging board but I want to be undefeated lol.

 

[Sideburn]

@Sideburn :

View attachment 58825

Oh crap duo you mean it is in charge of pulling reset low to get things started?

 

[Phipli]

Oh crap duo you mean it is in charge of pulling reset low to get things started?

Yes. The sound chip /does/ the reset. Thats why I was surprised to hear you removed them. I had to check that the IIcx worked like other macs from that time.

 

[Sideburn]

OK well when they were on there I had the same problem but I will put them back on and double check since i have made more repairs since then.

What if i manually pull RESET low and check the address / data lines? should I expect to see some square waves?

 

[GRudolf94]

If you manually pull /RESET low you should presumably see the machine come up, if all else was fine. Not sure if you're aware but always good to mention any signal name preffixed by a forward slash, exclamation mark, hash mark or with an overbar is taken to mean active low.

That said, you still have a few vias and traces that look dubious. Consider using thinner enamel wire for bodges, and also not using as much heat on the tants - they're much more predisposed to failure if baked golden-brown. Some of those parts (a few SOT-23s, some ferrite bead inductors) could do with some flux and a refresh.

 

[Phipli]

OK well when they were on there I had the same problem but I will put them back on and double check since i have made more repairs since then.

What if i manually pull RESET low and check the address / data lines? should I expect to see some square waves?

The board is looking pretty rough to be honest, I'd start by visually checking for more faults. You want to fix everything you possibly can before trying to bring it up. Its not easy to troubleshoot multiple faults at the same time so you want to minimise it.

Looking at your photos, it looks like you've been putting too much heat into the board, it might be worth turning down your hot air and iron.

Once you have made every repair possible, then start checking if the reset line behaves as expected, then you could check if VIA1 is switching the memory addresses to put the ROM at the bottom of memory.

Given the number of repairs you've done, it is very likely there are more hidden, so I'd expect issues under chips... like I spent the day chasing on an LC.

GRudolf94 beat me to a few of these things

 

[cheesestraws]

Agree with what's said above: if reset isn't being pulled low at startup but also isn't being pulled low by the reset switch, something fairly fundamental must be wrong with the reset circuit. I can't remember how things work on the IIcx, but on most Macs, the relationship between reset switch and CPU reset line is pretty direct and simple.

I fear you may be in for a bit of an adventure on this one.

 

[Sideburn]

If you manually pull /RESET low you should presumably see the machine come up, if all else was fine. Not sure if you're aware but always good to mention any signal name preffixed by a forward slash, exclamation mark, hash mark or with an overbar is taken to mean active low.

That said, you still have a few vias and traces that look dubious. Consider using thinner enamel wire for bodges, and also not using as much heat on the tants - they're much more predisposed to failure if baked golden-brown. Some of those parts (a few SOT-23s, some ferrite bead inductors) could do with some flux and a refresh.

Yeah the tats are burnt because a long time ago i put them on with hot air. i have learned since then,

 

[Sideburn]

The board is looking pretty rough to be honest, I'd start by visually checking for more faults. You want to fix everything you possibly can before trying to bring it up. Its not easy to troubleshoot multiple faults at the same time so you want to minimise it.

Looking at your photos, it looks like you've been putting too much heat into the board, it might be worth turning down your hot air and iron.

Once you have made every repair possible, then start checking if the reset line behaves as expected, then you could check if VIA1 is switching the memory addresses to put the ROM at the bottom of memory.

Given the number of repairs you've done, it is very likely there are more hidden, so I'd expect issues under chips... like I spent the day chasing on an LC.

GRudolf94 beat me to a few of these things

Yes i know this is a very rough board but not as bad as a vertex board i fixed. both got majorly corroded from being on the ocean front for years back in the early 90s.

Yes i was a total noob a couple years ago with the hot air gun when i put those caps on. i dont even use hot air anymore when i put SMD components on boards. only to remove them.

 

[Sideburn]

Agree with what's said above: if reset isn't being pulled low at startup but also isn't being pulled low by the reset switch, something fairly fundamental must be wrong with the reset circuit. I can't remember how things work on the IIcx, but on most Macs, the relationship between reset switch and CPU reset line is pretty direct and simple.

I fear you may be in for a bit of an adventure on this one.

Yeah.. I have fixed many boards now.. Amigas, ataris, vectrex, Asteroids coin op, etc.. i pulled this one out of storage just to give it a shot.. since its so bad... if it gets too crazy ill punt and use it as a parts board.

 

[Sideburn]

Sound chips back in and more bodge wires LOL

No change.. ARST goes high on power up.
Pins on the ROMS are going high and then low... so thats something...

 

[Sideburn]

I'll continuity check the sound area, the MPU area again in detail Theres probably some more broken traces I just cant see now. Thats why i have resorted to the O'scope now to hunt down the broken traces that just aren't visible anymore...