VIC serial bus issue

[majikeyric]

When I connect a working floppy drive or a SD2IEC device to one of my VICs, it is not detected,
I have a "device not found" message if I try a : load"$",8
like if the serial bus was faulty.

Is there a typical reason for this kind of issue ?

Thanks.

[joshuadenmark]

Often there is a device # sw on the SD2IEC device.

[srowe]

When I connect a working floppy drive or a SD2IEC device to one of my VICs, it is not detected,
I have a "device not found" message if I try a : load"$",8
like if the serial bus was faulty.

Is there a typical reason for this kind of issue ?

Thanks.

It could be one of the VIA chips blown. Does other I/O work, cassette, joystick, keyboard?

[majikeyric]

It doesn't come from the device number.

joystick and keyboard work, tape motor does not

[srowe]

The cassette motor is driven off CA2 of VIA #1, CLK and DATA of the serial bus are also on VIA #1, but so are three of the joystick lines.

You could try swapping the two VIAs, if you end up with no keyboard then you have a partially dead 6522.

[majikeyric]

Thanks srowe for the info,
Arf my VIAs are soldered, I can't swap them easily

[srowe]

Argh, the delights of a CR model. I fear that fixing this is going to be tricky.

[majikeyric]

I also own an old "2 prong" VIC that I can't use because I don't have the PSU.
I have verified the VIAs are socketed and not soldered on this one.

Are you nearly sure that it can mostly come from a faulty VIA ?

If yes, I can try to take off the VIAs (at least VIA#1) from the CR VIC20 (but I will destroy them), put sockets on it and try with the oldest VIAs.

[srowe]

I can't be certain but I know from experience that VIAs do fail. I had to replace both mine in the 80s, I can't recall how exactly I blew them but it's one of the few times I've toasted chips.

[majikeyric]

The faulty CR VIC20 was modded with a kind of reset button+speaker, inside the VIC, there were wires soldered to the serial bus connector.
I completely took off this mod because it didn't work and it must be the problem origin...

[Beardedmike]

joystick and keyboard work, tape motor does not

Looks like I may have the same issue, my tape drive will not work ( it works on my c64)
Would just a cleaning do?

[majikeyric]

Welcome to the forum Beardedmike

Im my case, a cleaning of the tape drive won't change anything

the disk drive does not work either. It must come from the VIA#1.

I have ordered a working couple of VIAs from eBay to repair that VIC.

[majikeyric]

I finally found the time and motivation to replace the VIA#1 of my VIC.

The tape motor now works but I still have "DEVICE NOT FOUND" when trying to access my working disk device

Do I need to replace the VIA#2 too

[Oge_user]

I repaired a VIC-20 with the same issue some years ago. Before replacing the other VIA, replace the 7406. You can also use a 74LS06.


Cheers,
Oge

[majikeyric]

WOW! thanks for the information Oge