68kMLA Classic Interface
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| Anyone up for some IIcx troubleshooting assistance? We have clocks but no activity... | |
| Posted by: joshc on 2023-07-04 08:00:24 Surface marks or actually cut traces? There's definitely some faded/dodgy looking traces there as well.  | |
Posted by: Sideburn on 2023-07-04 08:00:34I'm kinda running out of ideas here. My scratchpad now just has bad CPU and bad FPU. Even if there were broken traces that prevented it from booting, we should see more out of the CPU. You're absolutely sure it has good clocks, right? I would also check pins /DS and /STATUS (yeah, now the pin named as such)Yeah. Clocks are good. DA and Status are stuck high I believe from last time I checked. I agree. Seems like we’re running out of options. Plus the board is in such bad shape anyway. Just thought it’d be fun to pull off a “myrical”. Haha | |
Posted by: Phipli on 2023-07-04 08:01:28If it’s the cpu, it’s surprising to me since the area around it is is pretty clean. But if I could find one I have no problem swapping it out and socketing it if possible.Have you seen that max1zzz reverse engineered the PCB for the IIcx? You could build a new one using the custom parts from the dead one. This is a rare instance where it might be easier. | |
Posted by: Sideburn on 2023-07-04 08:02:28Surface marks or actually cut traces?No that’s something else. The board doesn’t look as bad as the pics. | |
Posted by: Sideburn on 2023-07-04 08:03:54Have you seen that max1zzz reverse engineered the PCB for the IIcx? You could build a new one using the custom parts from the dead one. This is a rare instance where it might be easier.I saw that. Pretty impressive. Well I have that other as-is one I bought yesterday coming. It’s got all the original caps but it doesn’t look bad. So I’ll try to get that one re-capped and up and running. | |
| Posted by: GRudolf94 on 2023-07-04 08:07:06 Looking at the '030 DS: STATUS should provide some clue of what the CPU is attempting to do - it literally shows the outline of what the core is doing. By forcing /HALT low you should be able to make the CPU show /STATUS also permanently low. You can try that. If that doesn't do anything, I'd reflow the CPU's clock pin, and the oscillator's clock output, etc, just for giggles, and if that does nothing...uh.  | |
Posted by: Sideburn on 2023-07-04 08:07:32I'm kinda running out of ideas here. My scratchpad now just has bad CPU and bad FPU. Even if there were broken traces that prevented it from booting, we should see more out of the CPU. You're absolutely sure it has good clocks, right? I would also check pins /DS and /STATUS (yeah, now the pin named as such)Here’s E1: | |
Posted by: Sideburn on 2023-07-04 08:10:22Looking at the '030 DS: STATUS should provide some clue of what the CPU is attempting to do - it literally shows the outline of what the core is doing. By forcing /HALT low you should be able to make the CPU show /STATUS also permanently low. You can try that. If that doesn't do anything, I'd reflow the CPU's clock pin, and the oscillator's clock output, etc, just for giggles, and if that does nothing...uh.Checking status again, status is low, halt is high | |
| Posted by: GRudolf94 on 2023-07-04 08:15:09 Ok, if /STATUS is low then it's permanently asserted and the CPU is telling you it's taken a double bus fault. If it's taken a bus fault you should see more signs of that. I would think you'd see some sort of address line activity, not just one pulse at reset - are you perhaps running the scope too slow for those signals? How does /STATUS act on reset? | |
| Posted by: Sideburn on 2023-07-04 08:19:05 I pulled halt permanently low and status and refill are high. | |
| Posted by: GRudolf94 on 2023-07-04 08:19:58 Ah, forget about that, it only had any relevance while we still thought /STATUS was never being asserted. | |
Posted by: Sideburn on 2023-07-04 08:20:55Ok, if /STATUS is low then it's permanently asserted and the CPU is telling you it's taken a double bus fault. If it's taken a bus fault you should see more signs of that. I would think you'd see some sort of address line activity, not just one pulse at reset - are you perhaps running the scope too slow for those signals?With halt not pulled low, status is stuck low and reset doesn’t effect it. | |
| Posted by: GRudolf94 on 2023-07-04 08:22:58 It doesn't ever change? Are you absolutely sure? What sort of timebase is the scope set to when taking this, and using what for a reference ground? | |
Posted by: Sideburn on 2023-07-04 08:26:44It doesn't ever change? Are you absolutely sure? What sort of timebase is the scope set to when taking this, and using what for a reference ground?GND is clipped to the rs232 port and continuity checked against the ground plane on the board. Time base is 50ns. But RESET pin on the 030 does not go low either when i press the reset button | |
| Posted by: GRudolf94 on 2023-07-04 08:29:16 Didn't you say yesterday that ARST was going low on the 030 as well? | |
| Posted by: Sideburn on 2023-07-04 08:29:53 I just clipped the scope probe to status and the. Pulled RESET low and status stays low. | |
Posted by: Sideburn on 2023-07-04 08:31:44Didn't you say yesterday that ARST was going low on the 030 as well?Yea and confirmed. Reset (F12) on the 030 is going low when I push reset and status stays stuck low. | |
| Posted by: GRudolf94 on 2023-07-04 08:34:21 So /STATUS just goes high if you tell it to halt? That seems broken, it's the opposite from what would be expected.  | |
Posted by: Sideburn on 2023-07-04 08:34:22GND is clipped to the rs232 port and continuity checked against the ground plane on the board. Time base is 50ns. But RESET pin on the 030 does not go low either when i press the reset buttonThis is incorrect sorry I meant STATUS stays low. RESET is going low when I press reset. | |
Posted by: Sideburn on 2023-07-04 08:37:10So /STATUS just goes high if you tell it to halt? That seems broken, it's the opposite from what would be expected. View attachment 58955Wait something is inconsistent. Status is staying low when I pull halt low but not always. Checking | |
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