Troubleshooting intermittently failing 1050 drive

[sideburn]

Hey all,

 

I have a 1050 drive that either works flawlessly or fails to read.

When it is in the working properly state, all tests pass using the 1050 Disk Diagnostic disk.

When it suddenly fails it fails motor, speed, step, settle, and track sensor tests.. the MPU STATUS Controller Tests all pass and then all of the rest of the tests fail.

 

When the drive is in the "non working" state, everything seems normal on power up.. Drive light turns on.. motor spins up, the track seek / stepper motor does its normal thing.. but when i put a disk in and power up, the drive spins up and it tries to read but just beeps slowly every few seconds trying to read the disk.

 

When in this failing state and I run the 1050 Disk Diagnostic disk and select troubleshooting and select the motor speed test, the motor spins up but the speed reading value is 0ms. 

 

When the drive is in a working properly state, the speed test shows good at 208.6

 

The power supply voltage looks good at 12v a/c.

 

Also it seems to not work at all when the drive is cold and when it warms up it starts working... for a while...

 

So it's seeming like I have a faulty chip. But which one? Bad RAM?

 

If anyone has any ideas or areas to check, please let me know.

 

I have an O'scope, DMM, etc for troubleshooting.

 

Thanks in advance for the help.

 

 

[Beeblebrox]

Do the large caps look OK? 

[_The Doctor__]

while it's open take note of orientation of chip / connectors,

then make sure to do a clean and re-seat of all the chips/pins sockets connectors and drive head,

blow out the sensors with aero duster,

check cap for bulging/leaking.

Check the power inside the drive when it's good and when it's failing, there is more than one voltage to consider as there is a 5v rail and 12v rail and an intermediate section between the two.

Could be that you have a cold solder joint, cracked trace or dirty selector switch (contact cleaner for that).

You might want to grab the field service manual from AtariMania or one of the Archive sites, this will give you test points and procedures.

Turning to aero duster upside down makes it  freeze spray, you can spray marginal components when it's working one at a time to see if they fail when cold and isolate them that way (just don't go crazy and make things soaking wet), You can spray them one at a time when not working and see if it makes it work as well, you would have to cycle power from time to time though as the drive might not be initialized properly as the bad component comes online.

Generally freeze spray lets you identify a component that is running hotter than it should by the frost dissipating faster than other chips and is quite evident. Marginal components may begin to work when ice cold. It's a quick and dirty method that works pretty well. generally if it stays icy for and extremely long time or melts instantly there may be a problem. Isopropal Alcohol wet dry method can show the same as it drys fast or stay wet longer but normally won't effect working state.

Best of luck.

Edited December 18, 2022 by _The Doctor__

[sideburn]

thanks, yes i tried freeze spray a while back and couldn't get it to fail.. I am going to crack it back open now and give it a more thorough inspection.

[sideburn]

Well I cracked’er open and then just realized / remembered I already did a full cap kit to it back in march this year. So the caps are not the issue. I also remember freeze spraying the chips. Anyway I just re-seated all the chips and it’s sitting here now on the bench apart and connected and doing boot errors. I’ll let it warm up and see if it comes back to life and then try the freeze spray again. 
 

otherwise I guess I’m going to have to go through the service manual and check some signals on the O’scope…

[+bob1200xl]

208.6??? Shouldn't it be 288.0? Sometimes the diskette is hard to turn in its jacket. Open the lever a little bit and see if the speed picks up. Slipping belt? Try a few other disks?

 

Bob

 

 

[_The Doctor__]

ah the old resquare the disk jacket method might be needed if disk is dragging, take disk perpendicular to rounded table edge and push just hard enough to put the edge flat and square again and repeat for all sides (4 total), this lets the disk spin freely again as it is no longer pinched by the jacket.

This isn't the drive that had the wonkey drive head connector at the pcb header end I hope. Sounds familiar

Edited December 18, 2022 by _The Doctor__

[sideburn]

45 minutes ago, bob1200xl said:

208.6??? Shouldn't it be 288.0? Sometimes the diskette is hard to turn in its jacket. Open the lever a little bit and see if the speed picks up. Slipping belt? Try a few other disks?

 

Bob

 

 

Yes. Sorry 288 was the reading when it is working. 

[sideburn]

3 minutes ago, _The Doctor__ said:

ah the old resquare the disk jacket method might be needed if disk is dragging, take disk perpendicular to rounded table edge and push just hard enough to put the edge flat and square again and repeat for all sides (4 total), this lets the disk spin freely again as it is no longer pinched by the jacket.

This isn't the drive that had the wonkey drive head connector at the pcb header end I hope. Sounds familiar

no this is looking more and more like a chip failure. 

[_The Doctor__]

I've seen folks forget the orientation of connectors and chips or have been off by a pin, had a bent pin or a crappy socket swipe, I have also seen the connector headers where the metal in the idc connectors have corroded or simply fell apart or out.

[sideburn]

Man this is a challenge.. Its completely intermittent.. I have swapped the drive mechanism with a donor 1050 and swapped out all of the socketed chips and power supply a/c adapter.

Some days it works for an hour and quits and the times it just refuses to work at all.

 

I have noticed when sometimes when it's in the failing state, when I power up the stepper moves the head forward only. it doesn't return to track zero.

Finally it will start returning to track zero again on power up and then its a 50/50 change the drive will read properly as well.

 

Other than it not reading disks and that startup failure, everything else seems to be working properly.

 

trying to figure out what component could possible be the issue...

 

Freeze spray does not help render any clues...

Edited January 3, 2023 by sideburn

[Peri Noid]

Sounds like a ROM or CPU problem... 

[xrbrevin]

36 minutes ago, sideburn said:

when I power up the stepper moves the head forward only. it doesn't return to track zero.

bad zero sensor alert! 😮

[TGB1718]

1 minute ago, xrbrevin said:

bad zero sensor alert! 😮

Had one do exactly this until I changed the sensor

[Beeblebrox]

If I recall I followed this YT guide at one stage:

 

 

Also here: https://atariprojects.org/2021/08/08/diagnose-and-fix-an-atari-1050-disk-drive-30-60-mins/

 

and a drop in replacement sensor: 

https://www.newark.com/optek-technology/opb842w51z/slotted-optical-switch/dp/73K1112?CMP=KNC-GUSA-GEN-DSA-PLA-OPTEK_TECHNOLOGY&mckv=sdUBRAClu_dc|pcrid|67429187781|plid||kword|_inurl:_brand:+optek+technology%23inurl:_product_type:+sensors+%26+transducers%23inurl:_product_type:+photo+interrupters|match|b&gclid=Cj0KEQjwiN6sBRDK2vOO_vaRs5cBEiQAfsnJCdmS35JeFxZnBa9W2C7QHapjCFqP197u0X5NCCZkMG4aAsWH8P8HAQ

Edited January 3, 2023 by Beeblebrox

[xrbrevin]

generic ones are available for cheap but you might have to swap the pin positions around to comply with the existing 1050 logic.

this is the case for the ones i bought but they work fine when you crack the 4-bit combination 🙃 (it was helpful that the component symbols are cast into the plastic casing - see pic)

 

 

 

[xrbrevin]

might be a bit expensive?

[sideburn]

On 1/3/2023 at 1:34 AM, Peri Noid said:

Sounds like a ROM or CPU problem... 

it’s neither. I swapped them out. 

[sideburn]

On 1/3/2023 at 1:40 AM, xrbrevin said:

bad zero sensor alert! 😮

I was wondering if it might be this. But when it does start working and returning to track zero it still doesn’t read fro the disk intermittently. If it powered up and initializes properly it’s still a roll of the dice if it’s going to read the disk. I’ve also swapped drives out and have the same issue so it must be something on the board. 

[Mclaneinc]

Maybe a reflow of the track zero sensor?

[sideburn]

I just made a video clip while it is NOT having an issue initializing to track zero and still having a read fail: https://youtube.com/shorts/-B40Y8Lfpow?feature=share

 

does this rule the track zero sensors? Same result on both drives but same logic board. 

[Vyvyan B.]

And yet you say it works perfectly when it feels like it after it warms up for a while. Thermal issue? As mentioned previously by Doc, cold solder joint. Bad socket. Cracked trace. You also said you recapped it. Were the old ones bad? You re-checked the solder joints on the new caps?

[sideburn]

Yes the problem is I’ve reflowed all over and deoxit rd sockets and header and freeze sprayed and it makes no difference. It just has a kind of its own you never know when it decides to start working. But it hasn’t in awhile now. Last time I powered up the head stepper only went forward. Now that’s working properly but reading still hasn’t worked in a while now. 

[sideburn]

I’ve swapped all the socketed chips and done a full recapping. 

[macsonny]

I know this might be a bit crazy but I've now had 3 drives that I've fixed by replacing the felt pads on the top of the read/write arm (head). They get worn and if the drive head doesn't apply the right pressure you get that exact problem. Have you tried replacing those?