The two small connectors have 5.1V on them.
They provide the 5V supply to the drive, then. Good, that means that you only need to change the connector to provide the power to a IDE-to-SATA or IDE-to-CompactFlash adapter.
If you compare to a standard PC peripheral power 4-pin Molex connector or the FDD power connector, only the red (+5V) and black (GND) wires are used:
The yellow is for +12V, and all black wires are ground. When the +12V is omitted, the ground next to it is usually omitted too.
The connectors on the left are the ones that connect to devices/adapters.
The 3.5" to 2.5" adapter only has 44 pins with a connector on the side. It doesn't mate with the one in the scope, so it was shoved in and held in place with hot glue.
Yes. The 40 pins are the same as in an IDE/PATA connector (on the scope), and the extra four pins are two grounds and two +5V power. The 44-pin IDE/PATA connector provides +5V to the device, and there is no separate power connector.
If you look at the device-side pinout of the 44-pin IDE/PATA connector,
then the two outermost extra pins are ground, and the next two pins +5V.
Instead of an adapter board (from 40-pin IDE and power Molex to 44-pin IDE/PATA), you could use a cable:
On the Molex connector, the outer pin is the +5V, and the inner pin is ground.
At the moment, the scope is no longer loading the OS (as I mentioned, I'm dealing with this issue in the HP newsgroup), but moving forward, I'd like to put a "normal" drive in this scope. For that, I imagine I'll need to figure how how to tap off the Molex power connector.
Since there is no +12V available, you're limited to 2.5" drives (both IDE and SATA 2.5" drives only use the +5V supply) and solid-state drive adapters to SATA SSD, SATA M.2 NGFF, CompactFlash, etc.
I don't understand why it doesn't have a SATA or Molex for a hard drive since this scope once had (I believe) a 3.5" drive. Someone must have went through the trouble of cutting wires.
Yes, I believe so, too.
I am not 100% sure if the bidirectional IDE-to-SATA adapters need +12V or not, so if you intend to get one, do check if it works without +12V first (noting that you should only use 2.5" drives that do not use the +12V). I
believe the adapters only pass +12V through and use the +5V for internal stuff, but the fact that many of them have two voltage regulators on them makes me wonder.
There were even in the olden days when IDE/PATA was used, drives that only needed +5V. It is possible that the connector you now have was originally a female 4-pin Molex with only two pins connected (+5V on the edge, and GND on the inner pin), and someone just cut it off, put that new connector on, and hot-snotted it in place.
Or perhaps the connector is original, and they just misplaced the adapter (from that to 4-pin molex or 4-pin FDD connector; possibly an Y cable).
Is it possible the motherboard was upgraded and drive power cables should be coming off it?
It is technically possible, but weirder than a grill in an ice cream shop. I've never seen a motherboard with peripheral power connectors; those have thus far always come straight from the power supply.
Since you are having problems with the current adapter, I would recommend replacing it with a cable. (You see, after looking into this, I suspect the adapter is broken, one of the solder connections being broken – it is a common complaint on the IDE adapters. The simple cable approach is more robust.)
For example,
this one from an US fleabay seller. Connect the two red wires to the +5V off the scope supply, and the black wire to ground. (I would replace the scope +5V connector with a molex one, scavenging an existing PC peripheral power cable (Y cables are a good source if you don't already have them), soldering the wires together (instead of de/re-pinning the connector).
To replace the existing drive and adapter, I would use the above, and a 44-pin IDE to slimline-SATA adapter, for example
this one also from an US fleabay seller. In other words, this is connected to the 44-pin cable above, and gets its power (5V) from the extra pins; no separate power cable. Again, I like the WD Green 120G and 240G SSD SATA drives, so that's what I'd use for the SSD drive itself. Your choice, though.
The SATA connector on these kind of adapters is notorious for breaking; they really cannot handle many detach-attach cycles at all. If you need to, get a slimline SATA extension cable (like
this one from the same US fleabay seller as the other cable), and leave one end always connected to the adapter.
This way, the adapter is basically "hanging in the air", so you might have to attach it to the scope chassis somehow, to stop it from shorting out anywhere. The adapter does not have any convenient attachment points, so the best option is likely to get a small plastic box for it, and saw/file room for the two cables on the long sides between the box and its lid. Or, if you have a 3D printer, print a small enclosure with it, with lots of holes in it for keeping it cool, in case it gets hottish.