My Apple][ has problems...(sob)

Greetings! I appreciate your interesting comment "it must be the DACs that are failing on the interface board. I tried heating them and cooling them, but that didn't change the results much." I don't know much about electronics, what are DACs?

I have 3 5 1/4 " disk drives:
- Apple Disk ][ (the disk speed is a bit "wobbly")
- clone half height drive (works very well, phew!)
- another clone half height drive (doesn't work)

As a maintenance practice, I run a disk speed utility, using the clone drive to boot up with, to align the disk speed on the Apple drive as best as I can. Opening the drive and adjusting the speed inside with a small screwdriver. Problems can arise from disks that were created/written to using a drive with a slow or fast disk speed when the disk is used in another drive. Data get corrupted! The disk speed utility stops the drives from excaborating this problem.

It doesn't quite sound like this is the problem with your DuoDisks but you never know.

I forgot to mention that it is an Apple IIe and that I have tried adjusting the "synch pots" on the duodrive but that didn't help either.

As the previous poster commented, you may have problems with
the drive spped. Try using a program like "Copy II" Utilities
and setthe drive speed pots using this. If that is not the
case, then try using another controller card as this is probably
the culprit. Sounds more like the controller card because you
have the same problem even when reversing the internal drive
connections. And don't forget the obvious. Check your cables
and connectors. They may be slightly oxidized after all that
inactivity.

Also, is it possible you stored the disks near magnets? Because they are MAGNETIC disks, and a magnet would corrupt them.

Unfortunately I can't get any program to load, not even my copy programs so I cannot compare. I did fiddle with the disk speed pots, but that didn't change much as from loading corrupted data it went to loading nothing at all. Also, I naturally checked all cables (DB Connectors) and unplugged and replugged them, but they're ok and nice and clean.

Thnx for the support in any case!

Yes, I am aware that magnetic fields, even weak ones, if maintained near a ferromagnetic source such as the ferro-oxide amalagamn which disks and tapes have will lead to realignment thus data corruption (a speaker, a small magnet etc). However, I have several boxes of disks in different places, not near any magnetic field, at least that I am aware of. Neither work so I don't think the disks are all gone - maybe some can be which already gave me some problems in the past (just a couple), but not all of them.

DACs are Digital to Analog converters, and to be more specific, the ones I was heating were the ADCs (Analog to Digital Converters). Data on magnetic supports is stored as analog, as it is an analog medium (modulated through Phase Shift Keying techniques and similia). The ADCs convert the sounds using a reference carrier or phase through bandpass filters to binary values. The amount of information you can squeeze into the disk depends on the bandwidth of your system and decode algorithm (how to extract the binary data from the "sound"). This is directly proportional to the speed of your disk, the quality of the magnetic media, the signal to noise ratios (S/N Ratio) thus the Bit Error Rate (BER). Every technology has it's limits, especially analog.

With time, al "analog" components (Operational amplifiers, Filters, ADCs and DACs which are basically analog) can drift in tolerance and response values due to instability of components such as capacitors or other internal arrangements. This introduces (even more) noise and other nasty trash in the decode stage and the data eventually is corrupted to a limit that the error correction cannot cope with it.

I haven't studied the components of the drive well, but it looks as if all the external board does is speed control and drive positioning (step motor control) mainly through the two Motorola ICs and additional drivers and logic. The data is then fed through the DB connector to the interface card where it is processed and decoded out to the Apple bus. I haven't taken down any IC numbers so I don't remember the lot but I'm quite sure there's some problem on the interface board (or the bus controller is flakey, but I doubt it). I will purchase another one if I can and if they ship to Italy (from the links on this board).

I was wondering if I could use the analog ports to play back a diagnostic program in compressed wav/PCM format someone could post or send me - if it is available.

Luke

My Apple IIe is alive again! The problem was a faulty dram chip on the motherboard. I ran the self diagnostic and it got stuck on "RAM:" so I went for it: I unsoldered all the 8 dram chips and soldered sockets back in, then I used my 64K expansion card's chips to replace the ones I just removed, and my Apple passed the test (KERNEL OK). So, using 7 good chips, I tested, one by one, the chips I had unsoldered and found a bad chip.

My disks all load fine, at least the ones I could try (I started playing Norad and Transylvania:). Now I just need to get a replacement chip, maybe from another expansion card which I can use as spare parts. I will be receiving also a Superserial card, which will expand my Apple further; I hope to get some more programs and xfer them using my PC to my Apple.

I'm happy again!

Luke

I appreciate answering my question about DACs. You certainly are knowledgeable about electronics. And I am glad to hear that your Apple is working.

cheers from mmphosis

Here are a couple of pics of my working AppleII:

http://www.applefritter.com/image/uid/13452

It lives!

Congratulations on getting the old IIe running again.

I have two IIe's and a IIgs. One of the IIe's belonged to my family when I was a teenager -- I could make that thing fly in my day.

The other two were given to me by clients who "didn't know what to do with these old things." I was very grateful to say the least.

I'm inspired now to dust of my own Apple II's and give them a whirl. Ah, for the warm green glow of a monochrome monitor!