VIC-1541 Question

[robert_sissco]

I recently picked up a VIC-1541 that was reported as not being detected. They said they would get a "Device not present" error when trying to load from drive 8.

From that and the after market hole on the back of the case, I figured that someone broke one of the jumpers and added a switch to allow someone to change the device from 8 to 9 with a flick.

I opened the case and there was a label over the jumpers noting "Switch for select 8" on it.

Simple fix I figured. I removed the sticker, cleaned up the residue with plans to just add a solder blob to re-bridge the jumper...and jumper 1 is on, it was lifted off of the board, likely when the person who got this removed the switch.

So, there is nothing for me to simple add a solder blob to. Annoying, but my question is what can I bridge on the board to basically restore this?

The PCB is noted as being 1540007 Rev B, and checking Zimmers I am not finding any schematics for that, but I did find 1540008-02, and checking that it appears that if I ground pin 15 of the 6522 in UAB1, I would restore the drive back to a hardwired drive 8.

Before I add any bodge wires, I just want to check if I am reading this correctly

 

[CommodoreZ]

I believe that is correct. I checked a few other sources, and those do be the correct pins that control the device select.

Ground away!

 

[robert_sissco]

OK, another question/issue on this drive. One thing I did not mention is that in an earlier attempt to repair it someone bridged pins 15 and 16 to the same point on L12 (a ferrite bead). On the multimeter this had pins 1, 15, and 16 bridged together. I cut these wires before I even powered it on, but now I have a different issue.

The drive is hardwired to 11 on the board (no biggie).

When I turn it on, the drive spins up (the motor was seized at first but this did not stop the activity light from turning off after a couple of seconds like normal).

When I tried to load a directory on my 64, I get the normal searching prompt, but no activity from the drive.

Now, I am thinking that perhaps the 6522 in UAB1 is fried. Even looking at the socket I can see soldering iron damage to the socket, but when I test with a multi meter I am getting connectivity from the chip legs to the soldering point on the metal of the bottom of the board.

Checking my spare parts bin I do not have a spare 6522 nor a W65C22N.

Is there anything I can check on the chip with a scope to make sure I am seeing activity? I am new to reading schematics so I am not sure where to back track on this, and would like some input as I am not sure what would be the best starting point.

Also, as I noted the motor was seized, but after I manually spun it with my fingers it started spinning on the power up as normal. Is there a way I can grease this to make sure it keeps spinning but avoid ruining the drive? Is lithium grease a good option for this?

 

[robert_sissco]

I literally just realized I can switch chips between boards.

I hate working 12 hour shifts.

 

[VintageVic]

>OK, another question/issue on this drive. One thing I did not mention is that in an earlier attempt to repair it someone bridged pins 15 and 16 to the same point on L12 (a
>ferrite bead). On the multimeter this had pins 1, 15, and 16 bridged together. I cut these wires before I even powered it on, but now I have a different issue.
>
>The drive is hardwired to 11 on the board (no biggie).

That's one of the older drives, I don't think I've had one.
But there's a cut from newer drive schematics. Still applies to yours.

Pins 15 and 16 control the device number. When shorted to the ground, your device number is 8.
Pin 1 of the 6522 is the GND of that IC. That is why those three pins are ... well, were bridged together.
When you cut the traces, you effectively made your device no 11, because you severed both pins 15 and 16 from the ground.

Your C64 is stuck at "Searching for..." and the drive does not respond? I guess one of your logic
chip fried which is directly connected to the serial socket. I don't have the schematic for that pdb,
but you could try to find which ic is connected to the serial port. I'm guessing it might be UC1 (7414).
UD1 (7406) might also be related, so I'd start from there, replace them with new and see how it behaves from there.

 

[robert_sissco]

Your C64 is stuck at "Searching for..." and the drive does not respond? I guess one of your logic
chip fried which is directly connected to the serial socket. I don't have the schematic for that pdb,
but you could try to find which ic is connected to the serial port. I'm guessing it might be UC1 (7414).
UD1 (7406) might also be related, so I'd start from there, replace them with new and see how it behaves from there.

That or the 6522 is possibly damaged. The socket for UAB1 and I noted earlier is damaged (soldering iron to close/on it when who ever did or removed the mod worked on it most likely) so a part of me is thinking that that might also be the problem, so when I finally dig my stuff out from the room rearrangement my wife and I are doing I am going to try and swap that 6522 with one I know is working, and if that fails I will check the LS chips, doing that last simply because those are not soldered in and I find desolding to be a pain.

If checking the LS chips still nets me nothing, I did find a spare board in a box I completely forgot I had that I can just try swapping it out for.

The physical read head was stuck when I got it but I got that fixed for now since I do hear it move when the drive now turns on, so I do not thing that this is the issue since the last drive I have where the head was stuck I would get an error after a while in BASIC.

But I do appreciate the input, and I will absolutely keep that in mind