1541 Drive - Drive Re-alignment

[Merlin]

An update....

The drive I have been working on works!!

I have a few original disks like Shadow and Vizawrite and it read those back perfectly. It is identified as device 8 on one of my breadbin C64 and as device 9 on my C64C . I'm not sure why that is happening, but I'll figure it out. Anyway, the directories read back really quickly with no drive LED flashing, which is excellent news.

Unfortunately, the breadbin C64 it works on has an iffy RF out and doesn't give a crisp picture on a TV. I have a spare board that does give a good picture, however, it can't see the disk drive, so I guess that some chip swapping is on the cards.

Onwards and upwards....

 

[TheCorfiot]

Merly

Ignore the RF out my friend, you can get composhite video & audio from the 5 -pin DIN port next to the serial DIN port.

http://pinouts.ru/Multimedia/AudioVideoC64_pinout.shtml


Standard 5-pin din socket, easy peasy

TC

 

[Merlin]

OK..

Following a little digging, it would appear from reading the C64 schematics that the 6256 CIA chip U2 has probably failed on the board with the decent picture. CIA chip U2 feeds the user and serial ports, so this is my prime suspect and they are prone to failure.

I'll change U2 over on the two boards tomorrow and see if the fault follows the CIA chip.

Stay tuned.....

 

[xc8]

OK..

Following a little digging, it would appear from reading the C64 schematics that the 6256 CIA chip U2 has probably failed on the board with the decent picture. CIA chip U2 feeds the user and serial ports, so this is my prime suspect and they are prone to failure.

I'll change U2 over on the two boards tomorrow and see if the fault follows the CIA chip.

Stay tuned.....

Swap and the CPU too...

also, check the 7406 (u8)

Chris

 

[Merlin]

I have replaced U2 and now everything works 100%. :mrgreen:

Now to move onto the second 1541 to determine what's wrong with it.

 

[AgentX]

Out of interest, how did you get the first drive working?

Now to move onto the second 1541 to determine what's wrong with it.

Is that the one with the flashing LED? If memory serves that means the DOS ROM failed its initial check. Could be partial failure of the ROM or corrosion of the ROM or its socket. Full ROM failures or power supply issues normally result in the drive constantly spinning and a solid red LED.

The first thing I would try is simply reseating the ROM. If that doesn't work then, providing the two drives are the same type, try the DOS ROM from this drive in the working one. If the ROM turns out to be okay I would suspect the socket.

 

[Merlin]

AgentX

That's exactly what I am going to try next. I'm getting three flashes from the red LED, so I suspect that it may be a dodgy connection. A quick wire brush of the legs and a re-seat of the chip may fix it. Stay tuned for progress....

The toggle switch that was fitted to the other drive selects device 8 or 9; very handy, if you are using two drives....

 

[Merlin]

Correction; the switch did select drive ID 8 or 9, until it decided to fall to bits . That was a brand new switch from Maplin and it's barely been used...

The knackered switch probably explains the drive 8/9 mystery that I couldn't track down. Putting a new loop of thinner wire across the two contacts to feed a new switch has the drive fixed as device 8. I'll get a new switch in the next couple of days.

Right now, I am kind of preoccupied with an abcess on the left side of my face and this is giving me industrial amounts of pain. I am on antibiotics and I feel like .....

 

[Merlin]

OK; time for another update.

I did some chip swapping on the other 1541 that was giving me the 3-flashes fault and it turns out that it was indeed one of the ROMs. When I swapped the ROMs from the known good drive, the faulty one fired up and read floppies perfectly - result!!

Further investigation has narrowed it down to the ROM 325302-01. TC has kindly offered to provide me with a replacement, in exchange for a 6581 SID chip for his C128 from my C64 graveyard - a fair exchange is no robbery...

Once the replacement ROM is fitted, I will have two working 1541 drives - one for my Mk1 C64 and one for my C64C - awesome!! The one with the switch is useful, as I can change the ID of that one from 8 to 9 for disk backup or file transfers between the two drives.

Now all I need is another 1541 serial cable...

/Merlin goes off hunting...

 

[ChrisUnionNJ]

I had my long 1541's setup so I could use 8,9,10,11 there are 2 solder pads
you had to use i'll have to dig up what pads were used been years..

Chris

 

[m4rk1z]

@Merlin

what's a c64 S model please?

 

[MoreBITS]

Interesting thread I am also working on a few drives that don't read.

Was there a problem with your first drive, or did it end up being just the media?