Panasonic JU-253-033P and NDOS floppies

FabFr

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Hi everybody,

I am facing a bit weird issue with one of my floppy drives. I restored few Amiga drives lately with success, but this one is not working at a 100% level.

It is a Panasonic JU-253-033P, found in many A500s. I did the following to the drive:
- Full dust removal and heads cleaning with isopropyl alcohol.
- Apply new grease on the heads motor axis
- Replace the 2 10uF SMD capacitors
- Align heads

Workbench disks and other Amiga DOS formatted disks will read/write flawlessly, not a single hiccup of the drive.
But when trying NDOS games disks, it will "freeze" at the same point while reading (disk keep spinning, drive led stays on until I do a reset, and a soft reset will bring a yellow screen)
Some games will "seem" to load but end to a totally garbled screen

Tried another JU-253-033P in the same Amiga : it works
Tried the weird JU-253-033P in another Amiga : it does not work

Does anybody have an idea of the cause of this? Any suggestion is greatly appreciated!

Thanks :)
 
Verify proper functionality of the drive's READY signal (e.g. put it in a generic external drive case and see if it's properly detected as DF1: under Amiga OS).
 
Hello,

@BLTCON0: I have a working external drive, "California Access" brand, I opened the case and swapped the disk drive inside with the Panasonic. Booted the workbench from DF0, then DF1 is doing it's clicking normally, but when inserting any disk it will fail to read it and end up in a DF1:BAD icon. I also noticed that the motor spindle of the panasonic is spinning slower when it's in the external enclosure, I am not sure if the small circuitry within the enclosure is responsible of this or not. Do you have any idea about that behavior?
I will try to check the PIN34 continuity and also check the "DriveTest" program from Aminet.

@roy_bates: Right now the drive is used in a standard untouched A500 rev6A, and I will plug it later into an A600 for use with the DriveTest program.

Thanks again :)
 
i have some of this drive not working, next week i verify with apposite tools
 
@BLTCON0: I have a working external drive, "California Access" brand, I opened the case and swapped the disk drive inside with the Panasonic. Booted the workbench from DF0, then DF1 is doing it's clicking normally, but when inserting any disk it will fail to read it and end up in a DF1:BAD icon. I also noticed that the motor spindle of the panasonic is spinning slower when it's in the external enclosure, I am not sure if the small circuitry within the enclosure is responsible of this or not. Do you have any idea about that behavior?
No idea, but the circuitry can't control the motor speed, so check the voltages. Normally the drive will spin up to 300 rpm. A significantly slower rotation will cause bitcell timing mismatch and invalidate the input stream.
On second thinking about testing in the external case though, disregard my initial suggestion. The ready line as used for drive ID is controlled by the circuitry so the drive isn't part of it. You should go the slightly less easy way and measure RDY behaviour on the drive itself (RDY should be normally high ~ +5V, and when the motor reaches full speed, which is within half a second once started, it should go low ~ 0 V and stay low as long as the motor is rotating at full speed.

I will try to check the PIN34 continuity and also check the "DriveTest" program from Aminet.
Yep, testing RDY trace continuity is of course a good idea as well.
 
Hello,

@BLTCON0: Well I think that the drive RDY signal works.
After checking the PIN34 voltage with multimeter I can confirm that it's 5V while the drive is idle, and become something low like 0.13V after the motor started spinning...

Is there any other part that could be verified to find out what causes the problem?

Thanks again :)

Envoyé de mon SM-N950F en utilisant Tapatalk
 
Hello and sorry for late reply, too much overtime in my work.

@BLTCON0 : I made a test with the 4 NDOS game disks and the results are these:
- Wrestlemania: will only read 1 sector then the display remains white, drive LED on and the Amiga is hanging up there.
- Knightmare: Will display black screen with large horizontal blue bars at top and bottom, loads few sectors and Amiga hangs up again.
- Puggsy: Will load sectors same way as working drive and then drive LED turns off screen stays black.
- Street fighter 2: Will load same way as working drive with the screen plenty of USGold logos. At the end of loading the drive LED turns off and the displays becomes red screen, the Amiga hangs up again.

Do you have any further suggestion?

Thanks again! :)

Envoyé de mon SM-N950F en utilisant Tapatalk
 
Nope no idea. Could be some peculiar misalignment not uniformly exhibited across the tracks. Try writing a full disk's worth of small files on a known good drive and floppy, and then checking if all read properly on the suspect drive. If some files fail, a disk editor can show you which tracks they reside on.


Also 4 NDOS games is a pretty low number... not a reliable sample.
Try with lots more :)


(are these 4 games you mention original, copy protected games?)
 
Hello,

I will try to make a disk plenty of small files this weekend and report you the results.

As for the games, I found a working NDOS one: Space Crusade. Loads fine both disks and plays well.
And yes, there are genuine games, as you see there :) 20180413_001754.jpg

Envoyé de mon SM-N950F en utilisant Tapatalk
 
Good morning,

I made the test yesterday and I noticed that sometimes and randomly the drive will have a "hiccup" but without displaying a requester message.
So I opened the drive and tried to adjust again the lower and upper heads with a flash light and a magnifier to make sure the notches of both heads are superposed perfectly.

It's a progress because now all the games I tested previously are loading except wrestlemania and knightmare.
I don't have an oscilloscope or special disk to investigate this further but I will try more NDOS games to see the drive's behavior.

Any advice is welcome.

Thanks again :)

Envoyé de mon SM-N950F en utilisant Tapatalk
 
Hello,

I could solve the problem!

Thanks for the advice and sorry for late reply (we have many days off during may here in France so I am more enjoying the weather than staying home)

Thank you for providing the Systest program, actually, I had already realigned the drive and tested it with formatting a disk or making a diskcopy then checking it, or copying many files.
But the problem with most NDOS games remained.

I mentionned earlier if there could be a problem with the PCB. Well that was the clue. I bought a spare Panasonic PCB from Airey (thanks again!) and I swapped it with my current one, without moving the sector 0 sensor board.

New test done: all DOS and NDOS disk are now working flawlessly! :)

Thanks again for all your advices!

Envoyé de mon SM-N950F en utilisant Tapatalk
 
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