i found out that there were ants coming into the monitor and getting thunderbolt attacked on the PCB, so each time the bunch of ants arced over the monitor flickered - Cleaning them out solved the problem

Gross. I am sure that smelled nice...

The 1st time probably happened in my absence. What i guess is, the fumes from the 1st ant attracted another few, that all came to the sme spot and burned there

Later the bunch would just randomly arc over from time to time, but there was nothing left in it that could really smell anymore (an an amount noticable over the normal "hot electronics" smell of the CRT itself) - It was probably a couple days there untill i realised that "that momentary flicker" was not just a one off event

I'm making progress with the Sharp PC-7000. First of all, the speaker is now working just fine. I found that as I repeatedly performed an action that made the computer beep, it was gradually getting louder and louder. Eventually it all-of-a-sudden sprang to life at full volume. I think the speaker itself was actually physically seized up!

Second, maybe I'm just getting used to it, but the display is very readable to me now. I look down at the screen instead of directly at it now since it provides much better contrast. I've looked up pictures of other examples of this computer, and their displays look similar, so I would say the display and associated circuitry is functioning just as it should on this unit.

There's one more problem to sort out. Now that I'm at Mom's house where all my floppy disks are, I've been able to actually boot the machine and use it, and I've discovered that the B: drive either has a dysfunctional head, or the heads are out of alignment. When I try to format a disk, any disk, in that drive, it detects it as a single-sided, 180k disk, and formats it as such. And it's always head 0 that does the work - head 1 appears to be the one at fault. But if I try to use the disk, it just corrupts any data written to it. It actually corrupted a couple of good disks with data on them that I tried. I've had the computer apart (for a computer of this type, it's surprisingly easy and intuitive to disassemble), and I've swabbed the heads with isopropyl alcohol, but that did not help.

Multimeter reading of head resistance (is the coil intact) ?

And what if its the controller, or a data bit on the bus at fault ? - Try to swap the controller PCB between the drives - one time leaving them in the same spots on the bus cable, one time swap that too

Try to swap the controller PCB between the drives - one time leaving them in the same spots on the bus cable, one time swap that too

No can do - the drives are a single proprietary module. They are controlled by one PCB, and have one connection to the motherboard.

More good news, though - After I posted my last message I tried formatting the same known-good disk in drive B: over and over, and after several attempts, it started detecting it as a double-sided disk, although head 1 was still failing on several tracks, and the format would conclude as if there were bad sectors on side 1 on the disk. As I tried again and again, the reported amount of bad sectors became less and less. Now it's able to format the disk completely fine, and I even successfully copied a boot disk's contents to it. I haven't tried other disks yet, but I now have hope that the drive may come out of it and start working fine, as well.

You can try to format with one sided parameter.  See the "format /?" to spit out the parameter information at the DOS box.

By the way, what DOS version are you using?

I'm using MS-DOS 3.2 since that's what I have on hand. I have MS-DOS 5 install disks though, so I'm gonna do an installation of that as soon as I re-write one of the install disks, which was one of the disks that drive B: corrupted.

One PCB is how most drives made nowadays - i dont see why it prevents swapping it (i assume the bus is the normal 34 pin one right ?)

Does this box contain a HDD ? If not are you installing to floppies ? Then you can install to floppies on another machine and use them in drive A of this one

One PCB is how most drives made nowadays - i dont see why it prevents swapping it (i assume the bus is the normal 34 pin one right ?)

I think what he means is that the floppy drives are a single unit, instead of two individual drives.  Looking at the picture, it looks like a single full-height drive with two slots in it, instead of two half-height drives.

icefoglights is correct - both drives are on the same PCB. They have separate mechanisms, but are contained within the same structure and have one connection to the motherboard and power supply.

OOh ok. I never realised they were single unit devices

At one point in time I had a double floppy drive that had a 1.44MB 3.5" floppy and a 1.2MB 5.25" floppy contained in a single half-height unit.  One power supply connection.  I believe both the power and data cables were 5.25" style on this drive, and the cable came with only one drive connection.  A jumper on the PCB was used to chose which drive was A: and which one was B:

I have a drive as you describe. But i thought it was a later concept, built as a retrofit for older computers that did not have 3 1/2 inch bays. I did not expect a 2x 5 1/4 drive to be made when 2 single drives can be used just as well..

I did not expect a 2x 5 1/4 drive to be made when 2 single drives can be used just as well..

They did it that way to save space and cables. This is a small portable computer after all.

Well, I've hit another roadblock. I re-wrote my first install disk of MS-DOS 5, tested it in another computer and it works fine. I boot the Sharp on it, and it successfully boots into the install introduction page, but as soon as I hit Enter to advance to the next page, the computer freezes solid. Also, I can exit the setup and go back to the command prompt, but as soon as I try to run any command, it again freezes solid, sometimes with garbage on the screen. I wrote another disk, tried it, same result.

Since the original owner of this machine upgraded from the standard 360k of RAM to the maximum 720k, I thought maybe one of the chips had a flaky connection. I re-seated all the chips; no dice. I tried removing the extra chips and the computer wouldn't turn on at all, so there must be a jumper that has to be set to indicate whether or not the RAM upgrade is installed.

So now I'm wondering what's up with that. Before the install disk originally got corrupted, I remember being able to advance to the next page of the install program, and then I think it froze up there, but I don't remember for sure. Perhaps I'll scrounge up a program to test the memory. I haven't had this issue with any other of the handful of software I've run on this so far.

These Sharp machines weren't known for following standards.

My question is where are you installing DOS?  From what I read on this machine, having the dual floppies means there's no hard drive.  I would think the most you could do for "installing" DOS would be formatting a floppy to be a system disk.