Re: Profile Drive issues (of course)

Just thought I'd post an update to this to the list...

Still no solution although some interesting observations. I've spent sometime reading the ProFile repair manual trying to get my head around what does on when the Lisa self checks and reads the disk as initiated by the host. I've grasped SOME of it and did a series of checks with scope and logic probe on various pins on the controller. Nothing untoward was seen. There didn't seem to be any stuck TTL gates.

Here is something though. I wanted to do some checks on analog board. To do this (due to the short cable) I had to flip the drive on its side and rest it on the controller board. I put a slap of styrofoam in the controller board to spread the weight of the heavy drive. Once I had done this the drive suddenly worked!!

Ah huh, I thought I had the answer. The cable. It was bent in a different configuration.

However, it WASN'T the cable. I checked it for continuity and it was fine. I also checked for continuity between the controller and analog board with the cable in place. It was also fine.

Flipping the drive again made it work but only one time more. The drive has now reverted to the same old symptom even on its side (and even upside down).

Then I suspected maybe a socket. The drive did put some weght on the controller board when it was sitting on it and distorted it a little. However it seems not. I checked EVERY pin of EVERY socket in the board. These sockets have a small solder pad on top of the board tucked right in beside the socket corresponding with each pin (and bottom pad) so they are easy to check. Using a featherlight touch I checked from the top of each pin to this pad. Every pin on every socketed IC checks out. None of them seems flaky.

So, there it is. I'm baffelled. The only thing I can think of is some dry solder joint on the controller board, although they all look fine. I'm assuming these top solder pads associated with each pin in each socket only show continuilty if the solder in the bottom pad is connecting with the pin but I could be wrong about this? If I'm not wrong, then it would limit any dry solder joint theory to non-socketed ICs or passive components.

Oh, I also checked the speed. It was a little low but within tolerance. I adjusted it to exactly the right speed but no change.

The frustrating thing about this is that when the drive does work it seems perfectly fine so I know the drive surface itself is not damaged (no need for a low level format). Also, in my experience ICs either work correctly or they don't. The drive works perfectly on very rare occasions so everything points to a connectivity issue. Just where that is though is proving difficult to track.

Anyway, I've spent hours and hours on the drive and I'm sure divorce proceedings will start if I don't take a break. You know what it's like though. You just don't like these things to beat you (-:

Terry (Tezza)

On Mon, Jan 23, 2012 at 10:51 AM, Terry Stewart <terry_at_email.domain.hidden>wrote:

> Thanks Shirl,
>
> I did have that Level II repair document, although oddly the one I had had
> a different introduction? It was in a document titled "Apple /// Computer
> Information • Doc # 78 • ProFile Hard Disk Repair Info". The bulk was the
> same though. I didn't have that profile schematic though. Thanks for
> pointing me to the folder. I'll explore those resources.
>
> Terry
>
>
> On Mon, Jan 23, 2012 at 8:51 AM, Shirl Casner <shirlgato_at_email.domain.hidden>wrote:
>
>>
>> There is a great collection of Profile hard disk documents on the
>> following site which may be useful for this Profile discussion:
>>
>> http://www.bitsavers.org/pdf/apple/disk/profile/
>>
>> The Level II repair document is quite detailed and shows how Apple itself
>> repaired these when they were returned to it by its dealers who handled
>> Level I repairs which was basicly board replacements.
>>
>> - David Craig
>>
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>

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