VOGONS

VERY strange HD issue in Texas Instruments Travelmate LT286-45

Topic actions

First post, by scruit

Posted on 
User metadata
Rank Newbie
Rank
Newbie

I was trying to replace the CP-3044 HD with an SD-IDE or CF-IDE adapter and every time I plugged in the adapter and powered the machine on I got a black screen no-start. Even other period HDs had the same response.

With the working HD connected (keyed by the blind pin) I did some oscilloscope traces of the ide legs under the HD (using the physical key as a landmark for picking which pin to 'scope). It showed normal-looking data/address lines but some pins were inverted, like the -reset line and gnd/5v showed wonky results. Then I suspected a black-screen dead could be a short, but not ALL of the devices I tried could be shorted, right?

Long story short - The IDE header on the motherboard is the wrong way around. And it looks like they used a drive with no shroud around the connector with a blind pin to key it instead.

The header on the motherboard has the physical "key" in the wrong position. The physical key and the blind pin are at odds with each other.

Look at this pic... Bottom left... https://i.imgur.com/VQS5LGj.jpg
This pic was taken during disassembly, prior to disconnecting things... And it worked in that configuration.
The #1 silkscreen "above" the pin does not match the red wire BUT the red wire goes the the #1 pin on the HD.

EDIT: WAIT A SEC - That's the FDD, 34 pins. THAT is reversed too?!

So, the fix was to take a throwaway IDE cable, cut the key off the HD end and plug it in "upside down". The pile of HDs that caused it to black-screen all work great now.

There has to be a story behind this....

Reply 1 of 2, by Deunan

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

Well, that's the first time I hear about IDE connector being wrong way around but I do have IDE cable without keys (not cut off by someone) which I guess was made for such occasions?
As for floppy drives, that I've seen. Sony is one particular brand I remember that had one 3.5" model with the key being on the wrong side. Got me too. Fortunately floppy interface is all open-collector with pull-ups so usually plugging it wrong will just make the drive not work (with LED on and possibly spinning all the time) - but nothing will short and die. Not for a few minutes anyway.

I do seem to remember that some OEMs bought these "weird" drives and installed in their machines. Not sure if on purpose (as a crude lockout for not-so-smart people trying to upgrade their machines cheaply by themselves) or was it just cheaper to buy these faulty drives and OEM wouldn't care much since they'd just tell the factory workers how to properly connect it.

Reply 2 of 2, by scruit

Posted on 
User metadata
Rank Newbie
Rank
Newbie
Deunan wrote on 2023-01-03, 23:41:

Well, that's the first time I hear about IDE connector being wrong way around but I do have IDE cable without keys (not cut off by someone) which I guess was made for such occasions?
As for floppy drives, that I've seen. Sony is one particular brand I remember that had one 3.5" model with the key being on the wrong side. Got me too. Fortunately floppy interface is all open-collector with pull-ups so usually plugging it wrong will just make the drive not work (with LED on and possibly spinning all the time) - but nothing will short and die. Not for a few minutes anyway.

I do seem to remember that some OEMs bought these "weird" drives and installed in their machines. Not sure if on purpose (as a crude lockout for not-so-smart people trying to upgrade their machines cheaply by themselves) or was it just cheaper to buy these faulty drives and OEM wouldn't care much since they'd just tell the factory workers how to properly connect it.

I just installed a cmos battery in there tonight and took the opportunity to double-check. Definitely inverted such that the physical key tried to put the #1 pin to the right, but the silkscreen shows "#1" to the left. Just a strange strange thing.

Go to top of page Go to top of page
Back to General Old Hardware
Close window
Close window