Commodore Plus 4 won't "talk" to disk drives!

[DistantStar001]

Basically what the title says. It's not talking to my 1541 or Pi1541. I try commands like "DLOAD", "DS$", and the old standard "LOAD"$",8" and the computer just hangs there. Also, it won't respond to RUNSTOP after it hangs. I've verified that the drives are working on my C64s and my C16. I also swapped out the TED and PLA since I had verified good replacements. The 8501 is also good. My suspicion is the 8551 or ACIA, since from what I've red, it appears to be involved in I/O communications, but I don't know enough about it (or TED machines in general) to be certain. As such, I'd like verification if I'm correct or to be steered in the right direction if I'm wrong before I take a soldering iron to it.

 

[DistantStar001]

It's the 8501. I didn't think it was since the computer booted, and did the same in my C16. But I did some more testing and noticed an odd error in BASIC. Basically, I ran the "HELLO WORLD!!!" loop. First as a 2 lines (10 and 20) and nothing printed. Then as a 1 line (10:20) and it worked as expected, but when I hit RUNSTOP, it reported a break in line 165. I listed it back and got: 165 PRINT"HELLO WORLD!!! ";:GOTO10

So I swapped it into my c16 and symptoms followed it.

Any ideas on a replacement? I've tried using a 6510 with no luck, and the MonoTech 6502 replacements are no cheaper than an actual 8501 from eBay once you factor in shipping.

 

[jltursan]

Yes, this one works pretty decently. You can purchase it already built from the project owner or simply as a kit much cheaper.