Seeking info. on Apple Drives

[tezza]

I'w wondering if anyone can help me with information/schematics etc. on this 5.25 inch disk drive?

It's an Apple II drive, made by Newtronics Co. Ltd. The Model number is D500. The numbers R69-0001 follow the model number on the case.

I got these two drives as part of the Apple haul. They have never worked, but while I have some test equipment I'd like to have a crack at getting them going.

The mainboard in one drive is completely dead. The mainboard in the other drive has cooked two capacitors in a most spectacular fashion! First, the one that was originally there when I first switched it on, and then a replacement sourced from the other board which was also exploded. I'm pretty sure I had the drive plugged in the right way this time. I figure there is a short-circuit on this board.

Problem is I can't do much without schematics. The letters on the cooked capacitor are indecipherable, it looks like + 111 u or maybe 10 u ? There seemed to be a u there before my pliers scuffed up the letters a but. Seems way to small to be 10 uf though? It's about the same size (if not smaller) as the blue caps on the board. 10 pf maybe but I'm sure it was a u not a p.

Anyway this code couldn't fit anything I could recognise. I'm can't really progress until I get a circuit diagram which tells me exactly what's happening on the board and what replacement capacitor I need.

I do have a couple of other working Apple drives as well as these two (and the TEACS) but they are different again.

Any advice or assistance gratefully received. I have higher res scans if anyone thinks that will help.

Tez

 

[Terry Yager]

My good man,

In my several years of attempting to acquire the knowledge necessary to repair electronic devices, I've not advanced nearly as far as you have in a few short months, therefore, I cannot offer any useful assistance in repairing your drives. I can, however, once again, offer you a pair of (working the last time they worked) A][ drives, if you are willing/able to spring for the shipping. (I'd almost be willing to cover the shipping cost myself, but I'm not quite that drunk yet, and NZ is sooo faaarr away). I understand your passion for fixing busted things, and I emphasize(sp?) (my FireFox spellchecker didn't flag it, but it just don't look right to me) with you in your effort, but should you find your drives to be a total write-off, I just wanted to remind you that my offer still stands.

--T

 

[tezza]

My good man,

In my several years of attempting to acquire the knowledge necessary to repair electronic devices, I've not advanced nearly as far as you have in a few short months, therefore, I cannot offer any useful assistance in repairing your drives. I can, however, once again, offer you a pair of (working the last time they worked) A][ drives, if you are willing/able to spring for the shipping. (I'd almost be willing to cover the shipping cost myself, but I'm not quite that drunk yet). I understand your passion for fixing busted things, and emphasize with you in your effort, but should you find your drives to be a total write-off, I just wanted to remind you that my offer still stands.

--T

Thank you for that generous offer Terry. I'll keep it in mind if I can't get these sorted. It would be nice to have two drives for every Apple II I own. With these two broken, I'm two short.

I'll have a crack at them first though.

Tez

 

[tezza]

Capacitor info

Capacitor info

Ah ha. While looking at my other Apple drives tonight I found the very same capacitor which blew in the two sick ones. They have completely different circuit boards but it's definitely the same cap.

The writing on it says...

STC
+ 10u (the u as in micro symbol)
+ 16v

10 microfarads and 16 volts I guess?

Tez

 

[Terry Yager]

STC
+ 10u (the u as in micro symbol)
+ 16v

10 microfarads and 16 volts I guess?

Tez

Sounds good to me...(but then, it is 5:30am here, and I am quite fit-shaced)...

--T

 

[cosam]

10 microfarads and 16 volts I guess?

Sounds reasonable to me, although so would 1.0uF! It'd be nice to have the schematics to be sure. Looks like a tantalum capacitor, hence the + symbol indicating which way round it goes.

In theory you'd need to be exceeding its 16V rating to make it blow like that unless the capacitor itself was faulty. Worth sticking a volt meter across before replacing it again but, seeing as the replacement came from a board of the same type and age, it's not improbable that it was on its way out anyway.

What's the deal with that green transistor(?) in the middle of the board? The hole near it could suggest it's meant to be screwed down. Has it been replaced?

BTW: Is the PCB made by Newtronics or just the drive assembly?

 

[tezza]

Sounds reasonable to me, although so would 1.0uF! It'd be nice to have the schematics to be sure. Looks like a tantalum capacitor, hence the + symbol indicating which way round it goes.?

Yea, its a tantalum allright. I've just looked up the web catalogue of our local electronics store and they do have 10uF 16V ones. I'll have to stop there on the way from home tomorrow.

In theory you'd need to be exceeding its 16V rating to make it blow like that unless the capacitor itself was faulty. Worth sticking a volt meter across before replacing it again but, seeing as the replacement came from a board of the same type and age, it's not improbable that it was on its way out anyway.

Possible I guess. Yes, I'll see what voltage I get over the pin holes when a drive boots.

What's the deal with that green transistor(?) in the middle of the board? The hole near it could suggest it's meant to be screwed down. Has it been replaced?

Hmm...without walking out to the shed, from memory only one board has that big hole. I'm not sure why? I don't think it is suppose to be screwed down into it.

BTW: Is the PCB made by Newtronics or just the drive assembly?

I'm not sure about that. Newtronics is on the brown PBC and also on the metal cast. I don't recall seeing it on the green PCB, but then I might not have just looked hard enough.

There certainly doesn't seem to be much info out there, although the name Newtronics does come up in relation to more modern drives.

Tez

 

[Terry Yager]

Sounds reasonable to me, although so would 1.0uF

It's a leetle large for a 1uF. I'm going with the 10. From my (limited) experience, the blue ones are somewhat smaller, like, mebbe 7uF-or-so...

--T

 

[cosam]

Hmm...without walking out to the shed, from memory only one board has that big hole. I'm not sure why? I don't think it is suppose to be screwed down into it.

Yeah, I don't think it's a problem. The hole looks a bit far off to be used for mounting anyway - was just wondering.

I'm not sure about that. Newtronics is on the brown PBC and also on the metal cast. I don't recall seeing it on the green PCB, but then I might not have just looked hard enough.

There certainly doesn't seem to be much info out there, although the name Newtronics does come up in relation to more modern drives.

I ask because, as you most probably know, it's common for manufacturers to build drives using their own case and controller PCB but a third party drive mechanism. In that scenario, searching for Newtronics probably wouldn't turn up the schematics you need. If drive itself is badged (externally) as Newtronics, that's a difference matter, of course.

 

[MikeS]

Not likely that you'd have enough voltage anywhere on that board to blow that cap, and of course it is possible that the replacement was indeed ready to blow, but one thing that is almost guaranteed to release magic smoke is installing a tantalum (or electrolytic) backwards in a low-impedance circuit. So when you replace it, make sure the + (or dot) is on the correct side.

And you might just confirm that it's DC across it, even though AC would be most unlikely.

You're putting some of us who've been at it longer than you to shame with your success rate and speed... ;-)

 

[MikeS]

How'd ya make out? I looked at mine in case I could help, but they're TEACs like your other ones with the adapter board on the back.

 

[tezza]

I am pleased to report both drives are now working!

The first one simply needed that capacitor replacing. You were right Mike, the replacement one I tried from the second drive (which blew also) must have just been too old as well. I was aware of the polarity and was sure it went in the right way.

The second drive was tricker. The problem was a short circuit caused by another faulty capacitor. This took some finding. The cap hadn't blown, but had become 100% conductive.

I should now turn my attention to my non-working PS/2, but I'd better come down from the garage workroom and spend some time with the family before they change the locks!

Tez

 

[Terry Yager]

If ghawd had wanted us to 'interact' with our 'families', he wouldn't have given us lockpicks!

--T

 

[scommstech]

I am pleased to report both drives are now working!

The first one simply needed that capacitor replacing. You were right Mike, the replacement one I tried from the second drive (which blew also) must have just been too old as well. I was aware of the polarity and was sure it went in the right way.

The second drive was tricker. The problem was a short circuit caused by another faulty capacitor. This took some finding. The cap hadn't blown, but had become 100% conductive.

I should now turn my attention to my non-working PS/2, but I'd better come down from the garage workroom and spend some time with the family before they change the locks!

Tez

Tez what sort of multimeter are you using, Analog or digital ???

 

[tezza]

It's a common old digital one. Why do you ask?

Tez

 

[channelmaniac]

Tez,

You need to get an ESR cap meter. They are basically a milliohmmeter running a high frequency signal through to measure ESR.

One alternate use for one is tracking down shorts on a board. As you get closer to the short the resistance goes down ever so lightly, into the hundredths of an ohm.

Also, those old tantalum caps short out after many years. When that happens they have a spectacular POP or throw lots of acrid smoke. It'll scare the crap out of you either way.

You could've checked where that cap was in the circuit too. If it's a decoupling cap across power & ground you have a LOT of fudge factor in replacing it.

RJ

 

[scommstech]

It's a common old digital one. Why do you ask?

Tez

Well Tez you can use an analog meter to test these type of capacitors.
You use the voltage on the probes on the ohms range to charge , and by
reversing the leads watch a good capacitor discharge. You can't do this with
a digital meter. I always preferred an analog because of this technique.
Doesn't work for the smaller value capacitors but its perfect for electrolytic.
Theres no guarantee however that when the full working volts is applied to
the capacitor it won't blow....
Digitals are better for setting up volts etc.

Regards.

 

[tezza]

Ah I see.

Yes, testing caps is one thing I wish I could do properly. In two recent repairs where the fault has been caps I've found them more by a process of elimination more than anything. In other words, it couldn't be anything BUT the capacitor. To the eye they looked perfectly normal.

That ESR caps meter sounds a useful device. I have to get a scope first though. I've only got a borrowed one at the moment.

Tez

 

[scommstech]

Ah I see.

Yes, testing caps is one thing I wish I could do properly. In two recent repairs where the fault has been caps I've found them more by a process of elimination more than anything. In other words, it couldn't be anything BUT the capacitor. To the eye they looked perfectly normal.

That ESR caps meter sounds a useful device. I have to get a scope first though. I've only got a borrowed one at the moment.

Tez

Never used a bridge for capacitors. Electrolytic are up to 20% +/_ value.
If the equipment is old, electrolytic are sure to be a problem. Some circuits can run without the cap., they are just extra smoothing. Most IC recommend using caps every few chips but its a precaution. Others will not run without them. You were unlucky that the drive caps were needed. Always double check the polarity when fitting electrolytic, they are unforgiving. If you come across the older larger caps with oil inside, be careful its toxic.
A scope is a must.
Regards