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Sharp PC-7000 Restoration


This is a Sharp PC 7000. A portable IBM PC clone released in 1985 when you picked one of these up for its original base price of $1795 US you would get two 5 ¼ inch double density floppy drives, parallel and serial ports, Detachable XT keyboard with a semi-proprietary RJ11 6P6C cable connection, and a backlit 640 by 200 monochrome LCD *beep* It has an Intel 8086 CPU and a base memory of 320K that is expandable up to 704. That’s right.
704 not 720 Now a 640 by 200 pixel display is pretty wide I’d shown this to someone who is curious to how DOS handled the extra wide screen aspect ratio So I figured I’d mention that here. In DOS, this shows 80 by 25 characters Which is typical for 80 columns even on 4:3 displays. But to make this display makes sense you should know that before 80-column was the standard, 40-column was the usual display size. For those who don’t know, The 4032 model number means that there’s a 40 character across screen with 32 kilobytes of memory So 4:3 displays were originally meant to be used for 40 columns. When computers added 80 column modes, only new horizontal space was added not vertical meaning both 80-column and 40-column only show 25 lines. So in a way, the extra wide display on the portable LCDs like this is actually more correct than the 4:3 desktop monitors Speaking of desktop monitors.
There were 4 extra options available for this computer. You could get it with a printer connected to the back, a 10 megabyte external hard disk that connected to the bottom an internal modem, or
the only thing mine came with the external CGA monitor connection. Conveniently out of all of them That’s the one I would want the most as the modem in CGA used proprietary connections inside the case and are not likely to be removed and sold separately. While we’re in here we can see that cool
Intel 8086 with a 1979 date code. which is… Kind of weird since that means
the CPU is six years older than the computer. All right now for the downsides this computer has some problems. *sad beep* Floppy disk drive B doesn’t seem to work at all And when the floppy drive motor is running the display flickers and when the backlight is off the fan runs faster, so I’m thinking the power supply is getting weak. And the keyboard cable is bad making it beep sporadically sometimes. Although I haven’t been able to capture that on camera. It sure has been annoying me while I’ve been testing this computer So let’s start with the keyboard cable first because that prevents us from being able to test anything else it may have seemed unusual at the start of this video that I knew exactly what kind of cable this was. And that’s because had a really hard time trying to find a replacement for it locally. Earlier I said, this is a 6P6C connector That means it has 6 positions and 6 conductors.
Unlike the two or four conductors that phone cables typically have. Well, I could order one online, I wouldn’t really be able to find one that’s coiled and the right length to be able to fit in the slot under the keyboard. So instead I ordered the connectors themselves, and I’m going to make my own cable out of Cat 5e network cable. Oookay… So The Ethernet cable didn’t work out.
I did fully make it and it did coil. But it didn’t coil as well as I’d hoped it would. Now I’d made a small little test cable out of the same Cat 5e, But I’d ripped out the internal insulation and the little thread that lets you strip back the external insulation and I’d removed one of the twisted pairs. So it was just the six cables that I needed inside. And that was pretty easy to make
and it looked pretty good but
the full-size cable didn’t work with everything in it And the cable was too long for me to remove that stuff from the inside because of the friction And it would just pull everything else out with it. So instead I found this other cable and I coiled it by wrapping it around a steel rod And heated it so that the insulation would soften on the outside And reform into the shape of the coil
which worked out really, really well! As far as coiling a cable goes
so I’m gonna remember that trick for the future. but putting the ends on this cable proved to be… So much more difficult than I anticipated. I recorded over an hour of footage of me trying to put the cable connectors on That’s not even counting when my camera’s 10 minute recording limit ran out and it just it didn’t record it So I probably spent 2 hours working on this cable and… Oh, it was so frustrating The wires inside are just too soft to try and jam into the crimp connectors like this So they would end up crumpling as I tried to fit them in. Eventually… Finally though after much struggle, I managed to get it to work
and I made a successful cable and I was able to test it with my
network cable tester and prove that it was indeed functional. And if I plug it into the computer itself and the keyboard, and power the computer up it does indeed work and Just for verification. I used it for a couple hours after that just with some software I had, and the cable held up very well. Now, it is a lot shorter than the original cable Which was not one of the things that I wanted to do I wanted it to be the correct length, but this was the only beige 6 conductor cable that I had on hand So I was just doing the best with what I had Eventually, I’ll order a proper vinyl insulated 6 conductor cable and I’ll remake this longer. So now it’s time to get back on track repairing the disk drives. After the nightmare that was making the keyboard cable. It would be really nice to have both drives be functional All right, I’ve got the floppy drive out, but I just want to stop and take a moment to appreciate how Incredible this thing is for 1985 It’s definitely bigger than a half-height Drive But it’s obviously smaller than a full-height drive like this Tandon and has twice as many floppy drives in it! Just wow, I tip my hat to Canon because this thing’s great And it’s even more impressive when you view it from the side. If we take a look at the tallest point on it we can see that it’s only About 10 millimeters bigger than the half high drive and it’s about half the total height of the Tandon Drive For reference if we put a CD drive on top of there because that usually fills up the entire Space in a half-height bay , we can see that there’s really barely anything at all sticking out Now, this isn’t the smallest or even the most useful dual floppy drive This FD-505 would easily take that crown since it supports different types of floppy disks. But this came out in 1992
and this came out in 1985. So this is much more impressive Plus it’s pretty obvious when you look at the FD-505, that they just kind of slapped a laptop floppy drive on top of a shortened 5¼. Well now that I’ve finished gushing about how amazing this tiny design is It’s time for me to eat those words because I still have to work on this thing. So way deep in here you can see the guide rails for the two heads And if I push on this one. You can see the mechanism move inside but what’s even weirder is if I move the other one you can see the other mechanism move both floppy disk heads use these same linear rails So It’s all one solid interconnected piece. So unlike the floppy drive restoration video I did It’s really really difficult to get the guide rails in there. So I’m not quite sure how I’m going to clean them Because I don’t think I want to take apart the entire drive because… ooh… that looks like a whole can of worms And unfortunately, I’m pretty sure I am going to have to get in there and clean those If I do the same head tension test that I did before with my tweezers.
I can see that drive ‘A’ moves quite freely But drive ‘B’ does not so Drive ‘B’ needs cleaned, but it’s not just that rail that needs cleaned It’s half of the rail because they each share half of the same rails One is just farther back, drive ‘B’ and ‘A’ is farther forward. So… Huh… -_- That’s going to be complicated. They’re just they’re so far down in there Jeez Now since it’s so hard to get in there what I’m going to do is put a little bit of oil on a Q-tip and try and feed it down in there and and Just apply the oil only where I need. Oh, I really hope it’s not bad bearings because these Pancake motors aren’t for spinning the motor. There’s a single solitary drive motor I think these are but it’s effectively direct drive. You can almost sort of see it in there These are actually what move the heads back and forth. So uh… Hoo…
Those really don’t look openable and serviceable. Although I can see some plate layers there. So… Ugh… I don’t know. It feels rough like… bad bearings not like… gummy… rails. Oh man,
it’s a shame It’s not drive ‘A’ that has the problem because I would just have to undo these two screws Which have nuts on the opposite side. Okay, the opposite two screws here and here
really easy to get to. The problem is that the drive ‘B’ motor has the same thing going on not here and not here on these screws But they’re on the underside of this plate. Which means that in order to remove the motor I would have to remove this plate But in order to remove this plate I have to remove the drive retention mechanism in order to remove the drive retention mechanism I Have to remove the drive head clamp Springs. It just it just keeps going on and on This is a much more difficult one to remove and try and work on. But this head it moves Somewhat freely so I think I’m just going to try putting the computer Mostly back to and see if lubricating the rails has made a big enough of a difference that it’ll just work if it has I know it’ll just be a temporary fix, unfortunately because I’m pretty sure there’s something wrong with the bearings in here on and uuuugghh… That’s it’s not fun. This number here is not a replacement model number…. This number HERE is not a replacement model number Looking up the drive model number in general Canon MDD-413 doesn’t bring up anything useful. So… Uuugh… I don’t know maybe this is a standard size pancake stepper motor, I don’t know it’s… I don’t know what that would be. So I’m sure if it is I’m going to let me know in the comments But for now, I don’t see a way of replacing those All right. It looks like drive B is now working correctly if I put a disc in there and try and read it We can see we do get the directory listing from it and What is even more reassuring is the fact that the disc I just booted from is actually a copy of the DOS disc I’ve been previously booting from so not only did it work for Reading a disk, but it was able to write a disk that another drive was able to read correctly So the alignment is correct on it and I may have made changes to that There are two variable potentiometers up here and I’m not sure that I didn’t make a change with those I played around with One of them specifically I can’t find any information on this thing Let alone a manual on how to tune it so I’m just kind of flying blind But it does seem to have helped. Now that the floppy drive is fixed Let’s go ahead and take a look at the power supply problem I’m measuring the 12 volt rail while the computer is booting up and you can see that it fluctuates between about 12.7 and 12.4 to 12.5 volts, so it’s really not dropping that much from the floppy motor moving Maybe the electroluminescent back lights just really sensitive to voltage changes because it’s only meant to be 12 volts So being up to 12.7 is probably fine. The 5 volt voltage rail is also rock-solid and just doesn’t change at all so I would say the power supply’s probably find overall Well I think that kind of takes care of all the repairs I need to do but while I have this thing mostly taken apart I should probably just finish the job and clean it up. So let’s go ahead and do that You And the restoration is now complete All right, so I already know what the first criticism of my restoration here is going to be and that’s that I did not Retro-Brite this and I’m just not set up for retro writing yet. It will happen I’m just not quite there at the moment. But now the computers ready. So let’s check it out All right, before we get too deep into this. Let me address the elephant in the room The LCD
it sucks It is every bit is hard to see in person as it looks there on camera. When I first got this thing I thought there was something wrong with my unit. but after I’ve looked at other people’s more recent videos of these but more importantly pictures of this when it was new I can feel assured That this is how it should be so for your sake it’s the viewer I’m going to go ahead and enhance it when it’s up close so you can make it out easier Just keep in mind. It’s not that clear in person Now, I’ve also seen several sites claim that this unit has the world’s first backlit LCD but I don’t put much stock in that. I think that in Sharp’s own sales brochure for this computer They probably would have loudly proclaimed that as a major feature not just mention in passing a few times back light is good though It’s not fluorescent LED or incandescent. It’s electroluminescent.
That doesn’t intrinsically mean it’s better but it gets the job done here It’s not super bright, but in super bright areas the display is reflective So it doesn’t really matter and no the contrast wheel for the LCD does not really help It just makes it darker or lighter overall. It’s not really useful for making the image clearer so now that we have it going let’s take a look at the main setup menu for this thing so we can go in and Adjust the clock and… wow you know, I meant to take out the battery, but it almost looks like it’s working I’m just not quite sure it thinks it’s January 39th here, but or 2019 I did actually set the date but Clearly something’s not quite right but we can adjust some of the features of this unit One of the really nice things we can do is invert the display and I’ll show you why you might want to use that later We can set the display mode from ‘Graphics’ to ‘Mono’, which does not seem to be… actually, maybe if I reboot seems to have worked and We are still in mono. Alright now, let’s try changing that to graphics Yep. Okay interesting. That could be cool and we’ll take a look at that in a little bit But for now, I want to go back to graphics. Okay now just a quick test to verify that drive B still works Yep, alright, so I am… Very happy with that. All right. Let’s try playing a game on here This is “Vette!” one of the few games. I have that says it will actually work on an IBM PC But more importantly this is one of the cooler ones I have. So let’s see what happens when we put the 360K disc in here and try playing it Alright, let’s go ahead and launch it Okay, so Vette! is one of the games that actually supports CGA with reverse color So we can just do that because the display is negative This is just… blisteringly fast… Yeah… Alright. Stupid, annoying DRM 16 Oh, yeah! Come on, turn! All right, so this is a little slow But Let’s see what we can do so first thing I may want to do is Change the speaker volume, to… low But here we have processor speed and we have the choice between standard and slow But I’ve also read this as standard and fast and this seems pretty unbearably slow for being PC compatible So, let’s see what happens when we run it it slow just in case that’s actually fast That is literally no different This doesn’t like it when you hit people great now, I’m gonna hit the… yep *snicker* Yeah, so I can press ‘E’ to turn on the end and stay on here Yeah, that’s no faster or slower. So hmm Let me try enabling standard speed Yeah, that’s no different so it kind of seems like… Turbo mode isn’t working Now, I did kind of show this working already earlier But this unit can use an external monitor because mine came fitted with the CGA option So with that we can have the internal display and an external CGA monitor connected and that does mean We can run the same game but on a proper color display. No inverted colors this time That seems like it loaded faster. I wonder if there’s a performance penalty for running the game in inverted color mode Which is actually why I mentioned the option to invert the color here Because we can just do it in the computer itself and then have the normal game display on there But let’s go ahead and see how this runs now maybe it will run better That’s getting really annoying engine sound but yeah, I don’t think that is any faster so Yeah, probably… Nothing to do with the inverted color mode Well that pretty much covers everything I wanted to say about the Sharp PC 7000 I think it’s pretty cool. Just as a portable PC compatible computer. Now I can say this is not the end of the restoration for this unit as I will be going back to do the Retro-Brite for 1 and 2, drive B Still isn’t quite right it puts on a good show, but it’s it’s got some issues. I’m not really… Happy with that. So I’m going to have to figure out something to Permanently fix that I don’t know what it’s going to be Maybe I can get the motor loose and maybe dribble some oil down into those giant pancake steppers. I’m not really sure. It’s… That’s not a that’s not a fun prospect But I’m also not Particularly fond of having to rely on floppy discs for this thing. While, there was a Sharp PC 7100 that would come with a hard disk instead of a second floppy drive and There is a 10 megabyte hard disk add-on for this unit. That would go underneath of it I don’t have either one of those so I do have to boot off a floppy disk Well, I’m wondering what’s the pin out of those internal connections? Specifically the modem since I don’t have that or really ever want a modem So I may look into seeing if the modem connection has a… Full ISA connection on it. But that’s something for a later video For now, I hope you guys have enjoyed that and I’ll see you next time

Glenn Chapman

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