Amstrad 664 - disc drive not working

[eto]

I have a 664 with a EME-150A disc drive. Yesterday I replaced the belt and it was working. Today I typed in "CAT", then the head moved a bit but then it did no longer respond.

When I now type in CAT the motor starts but the head no longer moves and the computer hangs forever. When I reset the computer (CTRL+SHIFT+ESC) the computer reboots but hangs before the BASIC prompt. I have to turn off the computer and then, after a CAT it again hangs forever. 

It probably is not the drive as the same happens with a different, working drive. 

I guess it's one of the ICs on the motherboard but I am not sure were to start the investigation.

[Rabs]

Does INP(&FB7E) return &80? This will at least tell you if the FDC is responding.

[eto]

Does INP(&FB7E) return &80? This will at least tell you if the FDC is responding.

yes, that works

[Rabs]

OK the FDC status is being returned, so the FDC and associated select logic is probably OK. I would run the Diagnostics ROM and see if the AMSDOS checksum is ok.

[Bryce]

Check the flat cable to the drive. You removed it to replace the belt and it may have loosened some wires. Also check the drive PCB (especially the sockets) for dry joints.

Bryce.

[xesrjb]

Sometimes solder joints come loose when you lift the circuit board to change the belt...

xesrjb 

I have changed nearly 50 belts or more and I had this problem approx. 5 times...

xesrjb 

[eto]

Check the flat cable to the drive

Will do. Thx.

Also check the drive PCB (especially the sockets) for dry joints.

on the drive? I checked with another drive which definitely works and it has the same issues, so it probably is the 664. Or do you mean the sockets of the ICs on the 664 PCB?

[eto]

So... still no change.

I tried with 2 different 3" drives and a Gotek, I checked for dry joints on the cable and the floppy related ICs, replaced the AMSDOS ROM and the 74LS38.

I recognized that |A has the same effect as CAT

Could it be the FDC 765? 

[Rabs]

Have a look at one of my fixes to a similar problem, may help, may not, but in your case the FDC is returning a good status value of &80.

CPC 6128 DISC MISSING BUT THE DISC DRIVE IS GOOD (cpcwiki.eu).

Symptoms;

• CAT returns that it cannot find the disk.
• But the disk drive is good and works in another CPC.
• If you ignore the CAT error 3 times the CPC cashes with a red screen.
• INP(&FB7E), the FDC status, returns &FF, but should return &80.

Root cause;

• IC203 74HC240 failed, causing errors when generating CS for the FDC.

[Rabs]

Guess the other difference is that on CAT your CPC hangs  rather than returns no disk.

[eto]

Guess the other difference is that on CAT your CPC hangs  rather than returns no disk.

right ...

I'll try the 765 today as (by coincidence) I just received a spare one. And if that's not the culprit, I'll order a 74HC240.

[eto]

So the 765 is also not the problem. 

Funny enough: After I replaced it, I could doe CAT three times, then it didn't work anymore. The disk behaved slightly weird, but it returned the directory. 

I then replaced the 765 again with another 765 but then also no CAT worked. 

So... HC240 will be next.

[Rabs]

Are you saying that CAT actually did return the files on the disk? Then stopped? So intermittent?

[eto]

Are you saying that CAT actually did return the files on the disk? Then stopped? So intermittent?

CAT returned the files. then I changed the disk. The next CAT also returned the files. In both cases the drive made a sound like the disk is hard to read. 

Then I tried another disk as I was not sure if the disk is fine or not. And then, when I typed CAT, the computer was hanging again. 

[Bryce]

If anything on the CPC side has failed, it's more likely that one of the 74 series buffers failed, rather than the 765.

Bryce.