The issue was with a STE machine, which was continuously or intermittently reporting the floppy was write protected when it was not.
The assumptions are the drive has been tested and working fine in another machine. It is also assumed that the WP pin on the 1772 is always high (for write enabled operations).
The fix for this issue to solder a 10K bussed resistor array to the 1772 databus pins as illustrated below.
The white wire connects the common pin on the resistor array to 5V.
ste_fix.jpg (68.33 KiB) Viewed 11731 times
Video below demonstrating one error without DMA pullups.
Re: Floppy write protected (when its not) fix.
Posted: Mon Dec 31, 2018 5:56 pm
by terriblefire
Just made this mod to my STFM
Hasn’t helped my issue but was easy to do
C8242480-1053-4E8D-8CB4-9FB.jpg (58.07 KiB) Viewed 11731 times
BAC020C4-60EB-4C31-9A95-5C7.jpg (114.94 KiB) Viewed 11731 times
Re: Floppy write protected (when its not) fix.
Posted: Sun Jan 20, 2019 1:09 pm
by PhilC
Just checking, as I dont have any 10k, do you think it will work with 4.7k?
Re: Floppy write protected (when its not) fix.
Posted: Sun Jan 20, 2019 1:16 pm
by exxos
Forgottenmyname wrote: ↑Sun Jan 20, 2019 1:09 pm
Just checking, as I dont have any 10k, do you think it will work with 4.7k?
Assume would be ok..
Re: Floppy write protected (when its not) fix.
Posted: Sat Apr 06, 2019 2:28 pm
by DoG
Did this on a STfm (070789-001 RevD) since I fitted 2.2 booster on it and having problem reading disks. Works perfectly now.
EDIT: v2.3 booster
Re: Floppy write protected (when its not) fix.
Posted: Sat Apr 06, 2019 2:30 pm
by exxos
DoG wrote: ↑Sat Apr 06, 2019 2:28 pm
Did this on a STfm (070789-001 RevD) since I fitted 2.2 booster on it and having problem reading disks. Works perfectly now.
Thanks for letting us know
Re: Floppy write protected (when its not) fix.
Posted: Fri Jul 31, 2020 10:10 am
by tzok
This fix solved my issue with ACSI CF adapter in 1040 STfm. Before, it was writing complete garbage on the CF card, after applying this fix - works like a charm!
Re: Floppy write protected (when its not) fix.
Posted: Fri Aug 13, 2021 10:28 am
by pixelk
Thank you !
As I didn't have the right resistor network, I built my own.
IMG_2021-08-13_10-21-42.jpg (511 KiB) Viewed 6374 times
Seems to do the trick.
Re: Floppy write protected (when its not) fix.
Posted: Fri Aug 13, 2021 11:04 am
by exxos
pixelk wrote: ↑Fri Aug 13, 2021 10:28 am
As I didn't have the right resistor network, I built my own.
Wow today's geek award goes to...
Re: Floppy write protected (when its not) fix.
Posted: Thu Aug 18, 2022 8:54 pm
by FujiMan
I'd remove the chip, put a precision socket in and place the resistor array on the bottom of pcb.
