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Tips on where to start on a non-working Disk II?

T

troj

Experienced Member
Joined
Apr 22, 2018
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115
Location
Bellevue, NE
Earlier today, I acquired an Apple ][+ from its original owner. With it, I received three drives -- two Disk II, and a 1/2 height drive of a brand I've not seen before. One Disk II works just fine, the other does not.

I'll disassemble it and clean the heads sometime this weekend. Assuming a thorough head cleaning doesn't do the trick, what other steps do those of you with more experience suggest I take? The drive does spin, but doesn't read disks at the moment.

-Kevin
 
Drive speed can also be an issue, speed should be set just a bit under the 300 Rpm mark
 
On getting a non reading Disk II, usually I try head cleaning then I next look to the 74LS125. Those are often damaged if the cable is plugged into the Disk II card incorrectly.
 
troj said:
Assuming a thorough head cleaning doesn't do the trick, what other steps do those of you with more experience suggest I take? The drive does spin, but doesn't read disks at the moment.
-Kevin
Click to expand...
Will it initialize a disk? Success at initialization but failure at reading all other disks is usually suggestive of motor speed that's out of order.
 
I need to find a proper fluorescent light so I can check drive speed manually. I tried Locksmith 6 and its drive speed test doesn't register anything at all.

-Kevin
 
You can most likely make something with a small LED. You can take 120V AC 60Hz and use a 0.1 uf capacitor ( rated for at least 250V ), a full wave bridge rectifier and a 1k resistor. Put the 1K in series with the capacitor then an input lead of the full wave rectifier ( not just a single diode ). Put the LED on the output leads of the rectifier. The other input lead of the rectifier to the neutral lead.
The resistor is to help absorb spikes. The capacitor is the main voltage drop. Use appropriate caution, dealing with 120V AC.
It should make a useful strobe.
Dwight
 
Try swapping the drives. Drive 1 plugged to the bottom, and Drive 2 to the top of your interface card. Then try and boot from Drive 2. If it works, then the problem is the interface card, if not then the problem is the drive. If it is the drive, then swap the analog cards between the two drives, and try booting again (do not replace the casing). If that works, then you can start swapping chips between the working, and nonworking cards to isolate the failed component. (note: do not attempt to boot from a disk that you can't replace/rewrite! As a defective a 74LS125 chip can corrupt data on the boot disk. If this chip is suspect, you will need to rewrite the boot disk with the working drive between boots). Also, be sure that the drives are plugged in properly as if they are offset on the controller card, the 5v rail will blow the 74LS125 regardless of whether that's your current problem or not. The next step, after you've eliminated defective ICs is to adjust the speed of the disk. To do this you will need a to write a diagnostic disk with ADTPro (DataLife Apple II Disk Drive Tester is recommended). You will need to boot from the working drive, then run your diagnostic on Drive 2 with the case removed. There are two potentiometers that will control the speed of your drive. The diagnostic software will tell you the speed as you adjust.
 
Don't fluoro tubes already to that? If its got the pattern on the bottom of the drive spindle then it may not pop a lot, but it should highlight the correct pattern.

A
 
Most small fluorescent lights are high frequency and no longer flash at 120 cycles any more. They rectify the AC to DC, filter and chop it to a higher frequency, like a switcher supply does. Some large shop fluorescents will still have the regular ballast but I don't know of any small bulbs that would work. The LED method I stated should work. It is simple to make with parts that are easy to find.
Dwight
 
A neon lamp powered by AC is an easier solution than rejiggering an LED to run on 60Hz, IMO. I've rigged up a pilot lamp like this one with a power cord, and it works well for stroboscopic rings on turntable platters and whatnot. I also have a vintage GE screw-base neon lamp like this one which I'm planning to put to use for the same purpose.
-Adam
 
AdamAnt316 said:
A neon lamp powered by AC is an easier solution than rejiggering an LED to run on 60Hz, IMO. I've rigged up a pilot lamp like this one with a power cord, and it works well for stroboscopic rings on turntable platters and whatnot. I also have a vintage GE screw-base neon lamp like this one which I'm planning to put to use for the same purpose.
-Adam
Click to expand...

Neon lamps are fine. Never said they weren't. The just need a current limiting resistor. They may be a little harder to come by, that is why I suggested the LED.
Dwight
 
Dwight Elvey said:
Neon lamps are fine. Never said they weren't. The just need a current limiting resistor. They may be a little harder to come by, that is why I suggested the LED.
Dwight
Click to expand...

I was just surprised it wasn't mentioned, since it's about the simplest solution. Sure, NE-2 bulbs aren't as easy to find as they once were (and NE-34s probably aren't even made anymore), but just about all 120/240V AC panel lamps still use neon bulbs, AFAIK, and have the appropriate current-limiting resistor built-in. The one I linked to is offered for sale at a local electronics store, and has an easily removed lens which exposes the neon bulb inside to make it easier to use for stroboscopic duties.
-Adam
 
AdamAnt316 said:
I was just surprised it wasn't mentioned, since it's about the simplest solution. Sure, NE-2 bulbs aren't as easy to find as they once were (and NE-34s probably aren't even made anymore), but just about all 120/240V AC panel lamps still use neon bulbs, AFAIK, and have the appropriate current-limiting resistor built-in. The one I linked to is offered for sale at a local electronics store, and has an easily removed lens which exposes the neon bulb inside to make it easier to use for stroboscopic duties.
-Adam
Click to expand...

I have a bag of almost 100 NE-2's someplace. My mention of using the LED instead was that it was more likely to be quickly found parts that one would have laying around. The diode bridge doesn't need to be high voltage. The capacitor is the only thing that might require a little searching.
It is true that most all lit AC switches use a NE-2, or smaller, with a resistor. In that case, one just needs the wires and plug.
Dwight
 
Dwight Elvey said:
I have a bag of almost 100 NE-2's someplace. My mention of using the LED instead was that it was more likely to be quickly found parts that one would have laying around. The diode bridge doesn't need to be high voltage. The capacitor is the only thing that might require a little searching.
It is true that most all lit AC switches use a NE-2, or smaller, with a resistor. In that case, one just needs the wires and plug.
Dwight
Click to expand...
A few years ago, I went into Radio Shack looking for some NE-2s, and was surprised that they didn't carry any. However, they did carry 120VAC power indicators which used them or something similar, and that's the basic sort of thing I put to use for checking stroboscopic disks on turntables and whatnot. When it comes to LEDs, I'd imagine it wouldn't be too hard to get the flicker rate wrong when building a power supply in order to allow them to be used on AC, making measurements incorrect. However, neon lamps have the advantage of being able to be natively used on AC, with the only supporting component needed being a current-limiting resistor, and flickering at the required rate without needing adjustment or assistance.
-Adam
 
It would be almost impossible to get the flicker rate wrong with the circuit I suggested. It is just the AC that is pulsing the LED. The rectifiers are there only to keep the voltages forward on the LED. It is intentionally unfiltered DC pulses. The pulses are at 120Hz, just like the NE-2.
Dwight
 
I thought every good tech carried a 4' fluoro tube in his toolkit :) I can understand the CFL's don't do it, but I'd never thought about how they worked any differently from the traditional tube.
 
Not all fluorescent lamps are created equal. Ones which use an old-fashioned magnetic ballast will likely strobe at the proper rate, while ones which use a newer-style electronic ballast might not. And ones which are battery powered (like most of the 4" fluorescent lamps I've seen) won't strobe at the proper rate at all, since they're not governed by line frequency.
-Adam
 
There used to be a drop light that had a ballast hanging from the cord. It was as a small transformer type ballast. It would work fine as a strobe. To bad I dropped mine years ago.
Dwight
 
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