1050 12V Issue?

[+Nezgar]

I’m usually offering advice for 1050 repair, but I finally have a drive I acquired that has a PCB issue I haven’t been able to solve yet, haha!

 

First, the stepper motor was jammed, so I was able to manually loosen it, and get it going again, so I thought I was done with the drive. Then the drive worked for about 10 minutes as I ran 1050 diagnostics which passed the basic tests, and RPM showed it was a little off. I turned off the drive to scrape off the blue Loctite off of VR2 so I could adjust it, and then found that the drive was unresponsive after powering it up again. Not sure how that could be related to the current issue, but that’s the order of events. Drive light powers up, but no drive spin, no head seek. With the mech connected though, I can hear a very faint 1 second or so buzz sound of what is probably the firmware trying to step the head to track 0 (if the head is not already at track 0) and a much shorter buzz if it’s already at track 0. So, I can tell it's able to detect the status of the Track 0 sensor because of this.

 

This 1050 I acquired seems to have had an interesting history of mods. First, the mech had the two red wires to the stepper cut, and replaced with spliced rigid solid core wires to the jumper block. No idea why this would have been done, unless somehow they were accidentally cut. I’ve never heard of a mod that required tampering with the stepper. The terminals in the jumper block were poorly soldered, but I redid those and that mech works fine in another 1050, so that narrows the issue down to the controller board.

 

On the PCB, the jumpers behind the ROM were poorly re-soldered back to the original JP1/3 positions, indicating it was previously configured for JP2/4 for an EPROM, but it has been returned to ‘stock’ configuration with the stock Rev. L mask ROM. The 6810 RAM chip has solder blobs over all the pins suggesting it used to be part of a homebrew US Doubler upgrade. The tops of the 6810 and CPU socket sides were broken off; suggesting replacement chips were plugged into each. This PCB has the really bad stock sockets that barely fit anything, holes that you can’t even see the wipes through, so it’s kind of expected... The CPU does not get replaced in the US Doubler upgrade, so maybe it was later switched out for something like a Happy, which does replace the CPU. All the sockets deserve replacing regardless…

 

Anyhow, back to troubleshooting – I verified the ROM and RAM chips are good by swapping with another 1050. Since I was not getting drive spin or stepping, I focused on the 12V power rail – it was measuring almost nothing, so I acquired a new 7812 regulator and replaced it today, but still no change. Well… I DO notice that the heat sink gets REALLY hot in the area of the 7812 within 30 seconds of operation, so something is causing a big issue there.

 

The 12V rail on TP14 shows 0.7V. The 5V rail on TP13 is a nice 5.01V

 

Replacing the 7812 (Q8) is the first troubleshooting step in the 1050 Field Service Manual, which I’ve done. Next it says to replace CR15 and CR16, which are just two diodes, and polarity testing those works as expected on the multimeter with continuity test. (CR15 is opposite polarity to CR16) Then it says “or” C71 – the 6800µf capacitor furthest to the rear of the drive.

 

Do these symptoms make sense to target replacing C71 next? Would a failed C71 cause Q8 to overheat and output very low voltage? Would tampering with VR2 have had any relation, maybe from jostling the cap in the process?

 

Thanks in advance!

Ryan

[+Nezgar]

I realized after posting that I hadn't touched the pins of that cap (C71) with the soldering iron, so I couldn't rule out an invisible cold solder/crack... but alas, no difference. showing 0.8V on the 12V rail. Just wanted to rule that out.

[+bob1200xl]

A short on the 12v circuit will draw down the voltage to almost nothing. Those big electrolytic capacitors cause all kinds of problems. Even the smaller ones can go bad.

 

Bob

[DavidMil]

How good is you multimeter? I had a dead short in a 1050 once and I used the continuity tester to find

the short. The lower the ohms reading to ground along the 12V trace, the closer you are to the short.

Turns out it was an internal short in a small electrolytic cap. Electrolytic caps a cheap and easy to get.

I'd start with them.

 

DavidMil

[xrbrevin]

i had a dead cap (small one: C70) and it became a short. this grounded out the 12v output from the 7812 and caused a similar failure

id advise check all caps, could be there is a cracked solder joint

[+Nezgar]

I compared ohms measurements with the multimeter on all the small caps, and most were the expected 'almost' 0 ohms, but C44 measured 13KOhms. I know it's not best to measure with the cap in circuit, but comparing with a working 1050, this same cap location measures almost 0 ohms over there, so I think that's a likely culprit, but I'll see if I can get the parts to replace them all today.

 

Thanks!

[E474]

Hi,

 

How did you manually fix the jammed stepper motor? I have a mechanism with a jammed stepper motor, but I don't want to just force it, as I think this might be unwise.

[+Nezgar]

How did you manually fix the jammed stepper motor? I have a mechanism with a jammed stepper motor, but I don't want to just force it, as I think this might be unwise.

 

In this drive, I only had to lightly tug on the head slider to get it to 'break free'. It was still really tight to slide along along the rails even afterwards, but exercising the mech by getting it to seek repeatedly from tracks 0-39-0, full disk sector reads, etc has loosened it up again over time.

 

I had a previous drive with a similar issue (it had lots of white aluminum oxidation, indicating storage in a humid environment) I used pliers on the top of the stepper spindle to turn it and break it free. It also worked fine after that.

 

I've never lubricated a stepper, as it looks like there's no easy channel to get it in without detaching it from the mechanism. Even if I did, that would require manual track re-alignment afterwards.

[E474]

OK,

 

I think the last thing I did with the mechanism was apply some light oil, maybe 3-in-1 or similar, but that was a few weeks ago. I'll try some light force (torque?) and see what gives.

[+Nezgar]

Arg! The local shop had all the caps on my list except one - the 2.2uf. Didn't remember that was the one I most suspected until I sat down tonight to get started. D'oh! Now I have to see where I can get one. so close! Was excited to fix this sucker lol.

[DavidMil]

Arg! The local shop had all the caps on my list except one - the 2.2uf. Didn't remember that was the one I most suspected until I sat down tonight to get started. D'oh! Now I have to see where I can get one. so close! Was excited to fix this sucker lol.

 

I have several 2.2uF radial caps. Let me know if you can't find them locally and I'll send you one (or two if you need 'em).

You should be able to get one at any major Electronics supply house. I use Mouser because they are close.

 

David

[+Nezgar]

Gotta love the generosity & resourcefulness of this community! Appreciate the offer - but I now have 2 coming in the mail from Saskatoon (next city ~2 hours drive north of me). 16¢ each +$3 shipping with regular mail. I'm happy they will ship such a small order, felt silly ordering so little. If I'm lucky I'll have them before the weekend.

 

Edit: Sigh. And then this happens... Pressure pad holder just fell out. Never know the history of these drives!! Glued the tab back on with testors plastic cement, but I'm not optimistic it will be any good when it dries. Maybe I'll touch it a tad with the soldering iron to 'fuse' the plastic after as often seen on 'retro recipies' you tube channel. (WST mech, maybe different part than the more common Tandon)

[DavidMil]

One thing I forgot to ask...

If/when you desolder the cap, did the voltage regulator stop getting hot?

If not, you've got another problem.

 

David

[Mclaneinc]

Do steppers cause a surge when they jam?...I would have thought they must?

 

Hope the cap sorts the problem out....

 

Best of luck..

[xrbrevin]

if youre reasonably steady-handed, maybe drill a v.small hole at the right height and use an 'R' clip? (the sort used on RC car bodyshells)

[_The Doctor__]

Yes, locked rotor can be a large current beast... if locked up and powered long enough can lead to burn some winding and such.. but I think he said he moved mech to other pcb and works fine so...

Edited January 9, 2019 by _The Doctor__

[+Nezgar]

Success!

 

One thing I forgot to ask...

If/when you desolder the cap, did the voltage regulator stop getting hot?

If not, you've got another problem.

 

David

 

Thanks for this idea, encouragement to do something now without waiting for all the parts.

- Removed my primary suspect at (C44 2.2µf) - no change

- Removed C51 1µf - no change

- Removed both C42 & C43, both 47µf, and now saw a solid 12V DC!!!

- Replaced C44 with the original 2.2µf, (the only one I was missing a new replacement for) - and still a nice 12V.

- Replaced C42, C43, C51 with new ones - still 12V

- Moment of truth! Connected the mech, powered it up, and it spins, and does the normal powerup head seek!

 

Now that it's back to a working state, I'll finish up by replacing the other two caps C69,C70, and can then proceed with replacing the damaged sockets....

 

Thanks all for the suggestions, appreciate the support!

 

.. but I think he said he moved mech to other pcb and works fine so...

 

Yep, the mech worked perfectly fine in another 1050. (And now the original one again haha)

 

Now back to the pressure pad thingy...

[Mclaneinc]

So glad its working and thanks for the info Doc...

 

Another AA happy finish.......oops.....

[DavidMil]

If the drive were mine Nezgar, I'd replace every electrolytic cap just to be sure. Flakey caps can cause all kinds of tiny

voltage spikes that will damage other components over time. But then I've always been know for overkill

 

David

[xrbrevin]

rise from your grave!!

[+Nezgar]

Just a followup with my continued adventures with this drive, and some pictures to enjoy!

 

First, the main topic of the thread, was replacing the 12V regulator (which did not resolve the issue), then replacing all of the small capacitors on the board. One of the two outlined in red was the actual culprit.

 

 

My focus then was on the absolutely horrible sockets on this PCB. First of all, these are the WORST of all the sockets Atari ever used... Not only are they single wipe, but the plastic frame has holes that are way too small, and most of the time upgrade boards like the Happy, Speedy, US Doubler won't fit. It appears obvious that a previous owner had difficulty inserting an upgrade or two, as bits of these sockets were breaking off prior to this photo. The WDC controller chip, and the 6532 RIOT pretty much never need to be removed, so I'm fine with leaving those sockets as they are.

 

 

So off with their heads!!! Easiest way to replace sockets is to just pull up on the plastic frames using pliers, revealing the individual pins/wipes which can be removed individually with the soldering iron and needle-nose pliers.

 

 

All of the pins are out! After, I used the good old spring-loaded solder sucker to clear out each hole.

 

Yup, all clear if you can see light through them all.

 

New machine sockets soldered in! These will survive many, many insertions/removals of chips! Hope I got the direction of the 28 pin socket correct.. those "AUGAT" sockets are kinda strange....

 

 

The chips are in! Nice and secure and reliable. The drive works great! This drive can now be confidently, and reliably upgraded to any number of 1050 upgrades.

 

 

Remember I was asking about suggestions on repair of the clips holding the pressure pad into the top arm? Well, my brain was out of ideas not being very ingenuitive. It turned out last week a coworker was going for training in California, so I just got Brad @ BEST to send him a replacement part to bring back for me .... He only sells it as part of a whole WST top arm. Well, I had a major facepalm when I saw the part my coworker brought back!! Brad's just GLUED a pressure pad plate into place! Of course that would work. Well, I feel silly I didn't think of that. Much more secure than gluing the individual clip like I was thinking. Oh well, a $15 lesson, and I have a spare now, LOL!

 

And last night I found that the RPM was not quite as stable as I would have liked, and found that the belt was pretty much holding together by a few hairs, and sections of the rubber have cracked/flaked off.. so on with a new belt, also from BEST. Lastly, the bottom spindle was making an unpleasant griding sound, so I spent some time working 3-in-1 oil into the shaft when upside down. Looks like the former owner tried to use lithium grease to lubricate it, as there was traces of it on the bottom, and it would ooze out when lubricating with the new stuff. I think the lithium grease dried out, and has left some residue that's causing the ball bearings to grind... the 3-in-1 has helped clean that up, it spins easier now, and should take less work for the 12V motor to spin it.

 

Rule-of-thumb: don't use lithium grease to lubricate 1050's.

 

Cheers all!

[_The Doctor__]

 

In this drive, I only had to lightly tug on the head slider to get it to 'break free'. It was still really tight to slide along along the rails even afterwards, but exercising the mech by getting it to seek repeatedly from tracks 0-39-0, full disk sector reads, etc has loosened it up again over time.

 

I had a previous drive with a similar issue (it had lots of white aluminum oxidation, indicating storage in a humid environment) I used pliers on the top of the stepper spindle to turn it and break it free. It also worked fine after that.

 

I've never lubricated a stepper, as it looks like there's no easy channel to get it in without detaching it from the mechanism. Even if I did, that would require manual track re-alignment afterwards.

needle and syringe application of lube works fine, no disassemble required...

[E474]

That's a great write up!

 

I have had to change a couple of sockets on a 1050, but I didn't remove the plastic socket casing as cleanly as you did, thanks for showing a nice example.

 

I always use Lithium grease for the drive rails, but I think you need something a bit more fluid/penetrating if you want to lubricate the upper/lower motor spindles. I have a backlog of boards and mechanisms that need fixing, so I really enjoy reading how others have gone about fixing up theirs (this isn't an aspect of enjoying watching others work, btw).

 

Also, is there a simple way to test if a capacitor is working (or in spec?), I'm gradually learning about electronics/electronic components, but it can be a bit much to take in all at once. The FSMs can be quite good at identifying which component might be damaged, but I think they assume more knowledge than I have when it comes to actually testing each component for damage. On the other hand, it's great that the FSMs (and other docs) are still available!

[+Nezgar]

I always use Lithium grease for the drive rails, but I think you need something a bit more fluid/penetrating if you want to lubricate the upper/lower motor spindles. I have a backlog of boards and mechanisms that need fixing, so I really enjoy reading how others have gone about fixing up theirs (this isn't an aspect of enjoying watching others work, btw).

Yes, 3-in-1 oil works great on the top spindle. Best if you remove it from the drive entirely, and disassemble it for the application. Dripping it in until saturation. Careful to ensure no drippage gets onto the actual plastic fingers that touch the disk. It seems to be quite a source of whine of the drives...

 

I spent a lot of time with a recent mech slowly dripping 3-in-1 into the BOTTOM spindle... it takes a lot of patience, but you have to think there's a lot more space and bearings in that side, and really no easy way to get the oil in except by seeping through the small circle at the bottom... Someone previously used some kind of grease there that dried up causing all kinds of racket inside (maybe I care more than others might) and it's been a heck of a time to quiet the subtle but annoying intermittent grind/squeak sounds....

 

Also, is there a simple way to test if a capacitor is working (or in spec?), I'm gradually learning about electronics/electronic components, but it can be a bit much to take in all at once. The FSMs can be quite good at identifying which component might be damaged, but I think they assume more knowledge than I have when it comes to actually testing each component for damage. On the other hand, it's great that the FSMs (and other docs) are still available!

I'm no expert, myself but at a high level I've read that to read the capacitance properly it needs to be first removed from the PCB, and then tested in a meter that can do capacitance... most multimeters don't have this. Mine doesn't.

 

With a DMM without capacitance, you can see if one is a straight short (0 ohms or continuity test instant pass) always open .. or a working cap will start with high resistance and slowly move to 0 ohms. I've found this only works on small caps, big daddys like the 1050's 4000+ohm caps take so much to charge that with the miniscule power coming from the DMM you won't observe the resistance drop.

 

And the big thing is that you can't actually measure the actual capacitance without the actual DMM feature... only that it has capacitance...

 

[+Nezgar]

So.. somehow the all seeing eye of facebook advertising picked up on my few searches about capacitor testers in the last few minutes, and led me to this cool looking thing - like $7 shipped from eBay/China

 

eevblog seems to find it agreeable... "winner winner chicken dinner"

 

not terribly accurate on capacitance, but good if you just want to confirm it's a good part....

 

pretty tempting at that price... tonnes of them on ebay