[FIXED] Help to make a JU257 floppy drive to work as a JU253 - Page 1
Forum section: electronics / repair

author: gkmaia
author_rank: Frequent Contributor
timestamp: May 04, 2020, 04:14:52 am
content: I got a faulty JU253A (5v) drive on my roland mc50 sequencer. Last image is the MC50 schematic pinout for the FDD.I bought a JU257A(5v) and now struggling to get it to work. The chipset is a FQL02030B4 and could not find a datasheet.Alt-ought the pins are the same apparently the 257 has a mode that allows it to record at the same density as a the 253.The current visible issue is that the disk when inserted in the 257 is not detected and therefor the disk use LED does not come on and the MC50 flags a no disk message.Maybe someone here with some knowledge on these drives that could lead myself towards the right path.

author: fzabkar
author_rank: Super Contributor
timestamp: May 04, 2020, 07:34:43 am
content: Page 38 of the service manual shows several jumper options for pins 1, 2 and 34. I think that may be the solution.http://www.bitsavers.org/pdf/panasonic/floppy/MSD871011300_Panasonic_JU-257_Service_Manual.pdf

author: gkmaia
author_rank: Frequent Contributor
timestamp: May 04, 2020, 08:03:58 am
content: My one is not really the one on that manual, but it is similar.I've attached an image of my board.I already adjusted the jumpers to RY, M0 and D0. My old 253 is set to these.Even after that I still get a solid LED on the drive. The drive spins and formats a disk all the way but in the end when it goes to verify the formatting it returns a data read error.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 04, 2020, 02:20:35 pm
content: Maybe theses can help ?

author: gkmaia
author_rank: Frequent Contributor
timestamp: May 05, 2020, 08:51:47 am
content: Thanks I had a look at those.I did a few more tweaks as the MC50 needs the ready signal on pin 34. That is done. Also needs the disk change signal on pin 2 and that is done. SMD jumpers are set to MO and D0.Put them both on a logic analyser and recorded them trying to load a file. Seems the ready signal is stuck on high on my JU257. Also drive 0 is stuck on low. Also the drive 0 signal is stuck on low on the Ju257.Any idea what the SW2 in/nc/out and SW4 in/out are for?

author: coromonadalix
author_rank: Super Contributor
timestamp: May 05, 2020, 12:10:22 pm
content: Density select ?? since you have a 720k floppy and the other is a 1.44 meg ??

author: gkmaia
author_rank: Frequent Contributor
timestamp: May 05, 2020, 08:53:26 pm
content: By looking at your PDFs seems that is throws a -HD or +HD signal on pin2 and that will mess things up... so better I leave those jumpers NCIf you look at the interface for the MC50 pin2 should be Disk change.I think at the time the MC was made there was only DD disks so the controller uses pin2 the old way.

author: gkmaia
author_rank: Frequent Contributor
timestamp: May 08, 2020, 06:34:03 am
content: Finally managed to convert the Ju257 to work on a Roland MC50 as a Ju253.I've attached and image if anyone needs to do the same.Need to lift pins 1, 2 and 34 of the IDC connector from the pads.Jumpers need to be set to M0 and D0.Then short the ready signal to pin 34. Short disk change to pin 2. Pin 1 needs to be disconnected. If pin 2 is left connected to the pad messes up the DC signal with Disk Density signal.