Choosing between three Sony MPF-920 drives

[exxos]

I know the sony chip caused many troubles, though a pull up sil on the DMA data bus would be worth trying to see if it helps with the sony chip or not. The drives do work, but seem to get progressively worse after some use.

My falcon went from working fine to not working at all with a sony chip drive in about a hour. Though I chucked out all my sony chip drives ,so never tried the DMA pull ups to see if that was the problem or not.

I can't remember if it was stfm or ste, but I had floppy issues which was solved with the sil pull up. Just something I never got around to looking into some more.

[Pacman]

You mean the Sony chip caused problems?
Please explain in more detail what you mean by the pull up on the DMA data bus. A pullup resistor connected somewhere on the DMA chip in the STe?

Do you think exchanging the PCBs inside the floppy drive would be OK? If I don't get the new drive to work (2001 model) I guess I have nothing to lose anyway

[exxos]

You mean the Sony chip caused problems?

Sorry, corrected my post, was past 1am when I posted, mostly asleep

Please explain in more detail what you mean by the pull up on the DMA data bus. A pullup resistor connected somewhere on the DMA chip in the STe?

Do you think exchanging the PCBs inside the floppy drive would be OK? If I don't get the new drive to work (2001 model) I guess I have nothing to lose anyway

Try it and see

[Pacman]

Yes, I know the feeling Zzzzzzzz.....

A couple of questions regarding your modification:

a) is that a 10K resistor array?
b) which value is the orange ceramic capacitor?
c) does the ceramic capacitor attach to the end of the blue capacitor on the PCB (C68) as I've illustrated with the red lines?

I looked up the STfm schematic but couldn't find any C68 nearby the DMA chip, then again it's not very clearly printed.
Is that the DMA chip which the resistor array and capacitor is attached to?

dma2015fix -added info.jpg (172.43 KiB) Viewed 8530 times

[exxos]

a) is that a 10K resistor array?
b) which value is the orange ceramic capacitor?
c) does the ceramic capacitor attach to the end of the blue capacitor on the PCB (C68) as I've illustrated with the red lines?

I looked up the STfm schematic but couldn't find any C68 nearby the DMA chip, then again it's not very clearly printed.
Is that the DMA chip which the resistor array and capacitor is attached to?

Ignore the capacitor...

The wire to the cap is just 5V. So you can pick that up wherever is convenient.

10K or 4.7K or 2.2K can be used.

[Pacman]

Understood.
And that's the DMA chip it's attached to it, right?
And it doesn't matter what kind of ST it is (ST, STe, STfm etc.) for performing this modification?

[exxos]

And that's the DMA chip it's attached to it, right?

Yes. Its the DMA databus.

And it doesn't matter what kind of ST it is (ST, STe, STfm etc.) for performing this modification?

Correct. I would do it on all machines just to be safe.

[Pacman]

I've just completed modifying (setting it to DS0 and adding a wire to the HD-detect switch so it can be used with the HD-module) my 2001 model MPF-920 E/131 (with the Sony chip) and it appears to work fine (in a Mega STe)! I haven't done any extensive tests, but did format a couple of HD and DD floppies using the desktop (TOS 2.06) formatter and Kobold, the latter with an extended number of tracks as well. One DD floppy wouldn't format properly, but I think it must be the floppy as another floppy worked OK.

With the Sony MPF-920 drives you sell you say "All drives are tested & working to the maximum extended format of 22 sectors 86 tracks.". Is this a matter of formatting them to those track/sector specs or can you recommend some more extensive tests in order to check if the drive is really OK?
The other test of course is to use it over time and see if it'll "go bad" as I understood some of your (Sony chip equipped) drives did.

[exxos]

The other test of course is to use it over time and see if it'll "go bad" as I understood some of your (Sony chip equipped) drives did.

On my falcon (and STE or FM) I had a few sony drives, some just refused to work at all. Others worked for a couple of hours, then started with random errors and eventually died. I got annoyed with them all and binned them in the end and the only drives left working were the BH ones.

Of course random errors can be dirty heads and bad floppies, but turned out sony chip drives were to blame in the end.

I normally just format several times with extended format, to check the upgrade and 1772 is working fine. Though at some point later, I never tested when, so really cant say, the drive just starts to refuse to read floppies and gets worse over a hour or 2 until it cannot read anything at all.

[Pacman]

Doesn't seem very promising for non-BH chip drives though my Sony chipped drive appears to work as it should (even with extended formats). Maybe mine can be the exception
Or maybe it's got something to do with component tolerances as I understand the conclusion was regarding the DMA chip, and in my case I've only been using the drive with an AJAX chip in the Mega STe. I also have a couple of 1772-02-02 chips so that could be interesting to try for comparison. It will also be interesting to see how it performs in the STe with your version 6 HD module along with a 1772-02-02 or AJAX. Adding 1.44MB HD floppy support this way in an ST/STe doesn't work in a much different way than how it does with the factory-installed 1.44MB support in a Mega STe, does it?

So you're saying that the drives that progressively got worse started out working fine, but within a couple of hours permanently became useless, or it worked fine again the next time you powered up the computer, then once again stopped working an hour or two later? Perhaps due to heat or something... Or maybe just one of those unsolvable computer mysteries