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Both 1050 drives gone bad


Rybags

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LDW and California Access drives used a 5v & 12v DC combined power supply but ive never heard of a 1050 converted to this.

you can buy generic power supplies with the above output voltages - they are intended to power IDE hard drives but i suppose they can be used as they have decent amp output

anyone fancy a try?

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Your power sounds good - don't mess with it.

 

The drive belt tends to stretch and skip a little. Crud builds up in the disk jacket, putting more load on the spindle. Watch the disk spin while you very slowly close the latch. The disk should just come up to speed evenly as  the latch closes.

 

Do you need some new disks?

 

 

Bob

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On 03/02/2021 at 6:25 PM, xrbrevin said:

LDW and California Access drives used a 5v & 12v DC combined power supply but ive never heard of a 1050 converted to this.

Behold: https://atariage.com/forums/topic/197540-1050-reset-mod/ (too bad the pictures are gone @Fox-1 / mnx )

 

 

Also the 7805 and 7812 regulators can be replaced with modern switching versions from tracopower or cheaper similar ones from various (china) sources: 

http://www.mathyvannisselroy.nl/Atari 1050 goes green.htm

 

 

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What's the accepted drift of speed?

I've done a high speed video and a strobe measurement by phone on one drive, looks like it's about 287 from the strobe, 288 on the dot from the video.   So looks like it's OK there, though I will remeasure it with a floppy present.

Edited by Rybags
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Well I'm fresh out of ideas.  Both drives seem fine re RPM with or without a floppy inserted (got RPM by doing a 240 FPS recording of rotation which conveniently gives 50 frames for 288 RPM)

 

Could it be something within the logic portion?  Like bad cap or an IC with dirty contact (though aren't these guys soldered in) ?

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18 minutes ago, Mazzspeed said:

as quite often newer switch mode power supplies aren't really suitable either.

Have to agree there, when I build something new, I tend to use older 'analogue' power supplies as I've gathered quite

a few over the years and can cover a wide range of DC voltages which obviously don't introduce high frequency noise

into sensitive circuits.

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11 minutes ago, TGB1718 said:

Have to agree there, when I build something new, I tend to use older 'analogue' power supplies as I've gathered quite

a few over the years and can cover a wide range of DC voltages which obviously don't introduce high frequency noise

into sensitive circuits.

And this is the problem, you have to use old linear power supplies. I have used a DC PSU before and tapped in before the bridge rectifier.

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On 03/02/2021 at 5:52 AM, Rybags said:

I was using an ED disk that has games on it (and doesn't matter if it gets wiped).

Do you have any SD disks you can try reading? If you have a spare disk it may also be useful to observe these drive's behaviour when trying to format a disk in SD vs ED if there are calibration differences between FM/MFM.

 

Did you ever by chance swap or replace the 2793/2797 controller chips in these two drives? It's important those remain with ther original 1050 motherboard as they are individually factory calibrated to each chip.

 

Check out this prior post from @tf_hh where he describes how to check the "125 KHz rectangled frequency for single density base clock, a 230 microsecond long impulse for precompensation (when using double density, MFM mode) and others" supplied to the 2793/2797 controllers:

 

 

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Neither drive has had any modification or been opened up for anything beyond head cleaning.  Format attempts get the same result whether SD or ED.

I've tried what I think are some SD disks but same result (generally the only disks I formatted to SD were full disk games)

 

I checked that linked thread - could it be possible some of my adjustable pots/caps have gone bad?

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@Rybags

It seem beyond strange are both dead. The only time I've seen such a thing was when a guy had blown out the sio isolation chips and also had drive select slide switch problems...

try deoxit and working the slide switches first... Have the drives hooked up all by themselves one at a time and try with a know good Single density boot disk. Make sure to plug the drive power supply into the wall last!

If the switches weren't the issue- move on to the chips u1 LM3086 is rattling around in my head, and u7 pia (6532)

T D

Edited by _The Doctor__
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I haven't tried a different computer - SIO2SD has been on the chain after the drive and it's fine.

The drives respond to commands as would be expected also (just that the result is obviously not what's wanted).

The ID switches are OK as I had different settings along the way which all worked.

 

But I might try another computer just to be sure though I'm not expecting any difference.

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Just a guess.. sounds like the read circuit is shot.  Makes me wonder if write works.  If you take a disk you know has data on it (by using some other floppy drive) and then format it on the busted 1050s, is the data then looking erased on a working drive?

 

Very odd problem indeed.

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Tried it without SIO2SD, yes.  "Working drive" - that's the problem to begin with, 2 now dud 1050s and an 810 that when powered up 10 years ago did nothing at all.

Like I said, the format fails.  I guess I could try a write operation but not holding high hopes.

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Update - I bought a multimeter that has frequency/duty cycle measurement.  Pulled one drive apart and tested for 125 KHz and got 124.9 reported (the actual test point is TP 9 for that).

Adjusting all 3 trimmers made no difference.

 

Wasn't able to get a reading on the other 2 points.

 

But now the big revelation - neither drive seems to write anything to the disk.  Both will commence and fail a format command doing the full 40 in/out steps but I've just determined that the disk itself isn't written to.  I was using a C64 formatted floppy to test and just got out that machine and 1541 and it's still a Commodore floppy.

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14 minutes ago, Rybags said:

Update - I bought a multimeter that has frequency/duty cycle measurement.  Pulled one drive apart and tested for 125 KHz and got 124.9 reported (the actual test point is TP 9 for that).

Adjusting all 3 trimmers made no difference.

 

Wasn't able to get a reading on the other 2 points.

 

But now the big revelation - neither drive seems to write anything to the disk.  Both will commence and fail a format command doing the full 40 in/out steps but I've just determined that the disk itself isn't written to.  I was using a C64 formatted floppy to test and just got out that machine and 1541 and it's still a Commodore floppy.

Have you tried another A8 yet? The odds of both drives failing identically are so remote, and basically I consider all the measurements you've taken thus far to be basically within spec.

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Tried my 800XL for the exact same result.

 

It's got me beat.  The only common elements - I've only got one 1050 PS though I just tried a 400 PS and got the same result, both drives not used for probably 4 or more years and stashed in my bedroom so not the worst environment with low to medium humidity most of the time and temps from about 8 to 30 C at worst.

 

I also pulled up and reseated the 6810, 6832 and WDC controller chips a little while ago.

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10 minutes ago, Rybags said:

Tried my 800XL for the exact same result.

 

It's got me beat.  The only common elements - I've only got one 1050 PS though I just tried a 400 PS and got the same result, both drives not used for probably 4 or more years and stashed in my bedroom so not the worst environment with low to medium humidity most of the time and temps from about 8 to 30 C at worst.

 

I also pulled up and reseated the 6810, 6832 and WDC controller chips a little while ago.

Replace any caps in one of the drives and see what happens. There shouldn't be many, I think it's best you work on one drive at a time to reduce diagnosis complexity just in case both problems are the result of different causes with identical symptoms. Which I think you're doing anyway.

 

Caps are cheap and easy to replace, at such an age they should be replaced as a matter of course anyway.

Edited by Mazzspeed
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