[toncho11]

My power supply cable for the HDD of my Indy melted just 10 minutes ago.
Luckily I see no damage to my SGI.

HDD1 is 80 PIN HDD with a scsi converter to 50 pin - my current drive
HDD2 some unknown 50 scsi - a new drive I wanted to test

So I decided to add HDD2 while HDD1 is attached (not on a running system) and upon powering up my Indy the cable connecting to HDD1 (not the HDD2 - the new one) melted. The plastic covering is almost gone. I tried the old configuration only with HDD1 and now everything is OK. 

I do not understand. The Indy does not support 2 HDDs on the internal scsi cable?
Or it is the 80 to 50 pin scsi converter (as this cable melted) that did something wrong?
A second HDD should be attached only on the external scsi bus?
Or just HDD2 was bad? But when I attached just HDD2 to the Indy before it was OK. No melting at least.
Could it be the power supply not supporting the load?

---

It was a short circuit I think. The power supply did not start, but it was slowly ticking.

[weblacky]

My initial thought is what we all fear...did you not put padding (cardboard) between the BACK of your SCA converter and the rear of the HDD? because if those solder joints coming out the back of your SCA converter touch the rear casing of your drive.......ouch.

Otherwise heat is caused by weak resistive connections. So I'd assume the connection between your female socket of your molex connector and the rear pin of the card's power connector wasn't flush, (in all the way), and was barely touching inside, causing Joule's law to take affect and create intense heat at the touch joint.

[robespierre]

If the power supply cable overheats, it indicates a short circuit on a power rail (+Vcc to Ground). The cable itself may be miswired.

This has nothing to do with SCSI cables.

[toncho11]

What is this padding (cardboard) of the scsi converter?

It was only the red cable, the 5 volts that melted.

On HDD2 (the new unknown one) it was marked "Polarized Plug" on the 4 pin molex power connector. What does it mean?

[weblacky]

What is this padding (cardboard) of the scsi converter?

There isn't natively any padding, I asked if you ADDED padding because often in SGIs (example is an Indigo2 sled in picture below).  Without any protection you have this:

   

Look at the arrows in this picture.  There isn't ANYTHING to prevent the backside (bare solder joints) of the adapter from touching the metal drive casing...for both part of the power connector and the SCSI signaling pins. Because this situation is dangerous, unless some insulated padding is placed between the  board and drive casing...you can easily bend the plugged in adapter enough to touch the drive with those silverly, sharp, solder joints on the rear of the card.  In a tight situation like an Indy...you can do something like this!

Did the two bare parts touch when powered on?  This touching (where the yellow arrows are) could lead to damage/fire/melting/bad stuff.

[toncho11]

What is this padding (cardboard) of the scsi converter?

There isn't natively any padding, I asked if you ADDED padding because often in SGIs (example is an Indigo2 sled in picture below).  Without any protection you have this:



Look at the arrows in this picture.  There isn't ANYTHING to prevent the backside (bare solder joints) of the adapter from touching the metal drive casing...for both part of the power connector and the SCSI signaling pins. Because this situation is dangerous, unless some insulated padding is placed between the  board and drive casing...you can easily bend the plugged in adapter enough to touch the drive with those silverly, sharp, solder joints on the rear of the card.  In a tight situation like an Indy...you can do something like this!

Did the two bare parts touch when powered on?  This touching (where the yellow arrows are) could lead to damage/fire/melting/bad stuff.

Actually you are right!!! It could be the source of the problem where 5V touched grounded surface. I am thinking what kind of padding should I use.

[weblacky]

Cardboard from like a cereal box, multiple layers, normally works okay. As long as those solder joints cannot poke through. Also you'll need to steal a replacement molex power connector for your cable (pins slips out). Just try to replace as much if the damaged parts as possible as they wont make a good connection anymore. Be safe.