Sharp PC-5000

[darkscreen]

Hello
I have a Sharp PC-5000 with a broken internal power supply. I need some informations about the internal power board like the service manual or the pinout of the conector to the mainboard. The external power supply works and I get the 15V to the internal board but no output to the mainboard connector. It would be helpful if someone has pictures of the internal power pcb.
Greetings
Darkscreen

 

[voidstar78]

I do have a copy of the Sharp PC-5000 Service Manual, mostly in English and has many schematic diagrams.
So far I'm not seeing a digitized version of this manual
CODE 00ZPC5000S/ME
I have seen some spelling errors and technical mistakes in the manual (suggesting it was translated, and might apply to very early editions of the system before production model was final). But still a good reference.

I opened my PC-5000 in an attempt to replace the RTC battery - but I was unsuccessful at the time, since all the tearing down involved I felt I might end up doing more harm than good. My notes on this are in Category 4 of the following:

Sharp PC-5000 Archive Notes — xiphod

(click on images below for larger view) A video covering this system is now available here! TABLE OF CONTENTS Introduction In November 1983, Sharp released a “portable office” system called the PC-5000. This had a 640×80 dot LCD (no backlight) and 128KB bubble memory cartridges, using an Intel...

voidstar.blog

There are two diagrams for the power circuits, will try to capture them

 

[voidstar78]

Not sure if this is enough info to help? Can try to get a better capture, if this is in the right direction.

Notice the "Power Supplay" is the kind of misspellings I mean. It's cute

 

[darkscreen]

Thank you for the pics. It helps a lot. I hope that I can bring my pc-5000 back to life.

 

[nevergrownup]

Thank you for the pics. It helps a lot. I hope that I can bring my pc-5000 back to life.

Were you able to get your Sharp PC-5000 working again? Recently got one working. Happy to help with diagnostics/readings from a working example if it's still a project for you.

 

[darkscreen]

Were you able to get your Sharp PC-5000 working again? Recently got one working. Happy to help with diagnostics/readings from a working example if it's still a project for you.

No my Sharp is still not working. Cool that you got one! My problem is the PSU, I am still searching for a service manual with the voltage of the power connector, so that I can try with a different PSU.

 

[smbaker]

@nevergrownup and @darkscreen and @voidstar78 I've joined the club on PC-5000s with nonfunctional powersupplies. Darkscreen did you ever get yours working? and Nevergrownup what did you do to get yours working?

I've supplied mine with +15V, center negative to the power supply, but it does absolutely nothing. Doesn't even pull a measurable amount of current. I don't think it's something so easy as bad capacitors, but could be bad rectifier or (worse yet) one of those potted subassemblines on it.

A list of power supplies to the main board would be very helpful, then I could at least replace it with something else.

Scott

 

[nevergrownup]

@nevergrownup and @darkscreen and @voidstar78 I've joined the club on PC-5000s with nonfunctional powersupplies. Darkscreen did you ever get yours working? and Nevergrownup what did you do to get yours working?

I've supplied mine with +15V, center negative to the power supply, but it does absolutely nothing. Doesn't even pull a measurable amount of current. I don't think it's something so easy as bad capacitors, but could be bad rectifier or (worse yet) one of those potted subassemblines on it.

A list of power supplies to the main board would be very helpful, then I could at least replace it with something else.

Scott

@smbaker I was fortunate enough that the PSU on mine worked without repair. I think I replaced some caps just in case, but that's it.

If I get a chance tonight I will pull it up on the bench, take a few pics, and try to mark some of the outputs and what they are reading so everyone has a baseline from a working system.

Also, @darkscreen I apologize, somehow I completely missed your reply back in August so I didn't get the voltage reading to on the power connector over to you.

 

[smbaker]

Thanks @nevergrownup. If there was any way you could measure the current draw between the battery and the PSU when operating, that would be useful. I've found that mine will consume power if I supply +6V to the battery connector (as if a battery was connected), but quickly spikes to around 2A of power consumption which sounds like too much. There's also a bit of a squeeling sound, which could be a boost converter misbehaving. I'm not sure whether the computer is capable of being powered from the barrel jack on the back alone, or if it needs battery to provide current boost. Since it reacts to voltage at the battery connector, at least the second stage "does something" unlike the first stage of the power supply, which does nothing.

The diagram voidstar uploaded above will be useful, as it has the power leads marked with names. If we had the rest of the schematic, it would be even more useful to be able to determine what these wires did. At least a couple of them are marked as being for the LCD. Another one has to be for the clock.

I will probably recap mine as well.

 

[nevergrownup]

Thanks @nevergrownup. If there was any way you could measure the current draw between the battery and the PSU when operating, that would be useful. I've found that mine will consume power if I supply +6V to the battery connector (as if a battery was connected), but quickly spikes to around 2A of power consumption which sounds like too much. There's also a bit of a squeeling sound, which could be a boost converter misbehaving. I'm not sure whether the computer is capable of being powered from the barrel jack on the back alone, or if it needs battery to provide current boost. Since it reacts to voltage at the battery connector, at least the second stage "does something" unlike the first stage of the power supply, which does nothing.

The diagram voidstar uploaded above will be useful, as it has the power leads marked with names. If we had the rest of the schematic, it would be even more useful to be able to determine what these wires did. At least a couple of them are marked as being for the LCD. Another one has to be for the clock.

I will probably recap mine as well.

@smbaker The machine will operate fine with no battery installed. While I have the battery from mine and it is in good physical condition, I removed it and I keep it separate in a plastic bag in case it ever starts to leak and I do not bother to install it even when running the machine.

 

[voidstar78]

for ref,

SharpPC-5000/Sharp_PC-5000_ServiceManual_October1983_compressed.pdf at main · voidstar78/SharpPC-5000

Contribute to voidstar78/SharpPC-5000 development by creating an account on GitHub.

github.com

Let me know if still not high enough resolution - maybe I'll go ahead and tear the binding and scan pages properly.


Also my PC-5000 video (but not a tear down):

And I have an STL model of the compartment cover. I did in TinkerCad and have printed in both PLA and ABS, fits well for me. Also did a translucent print, so you can semi-see what's inside the compartment without opening it.

SharpPC-5000/PC5000 CoverT.stl at main · voidstar78/SharpPC-5000

Contribute to voidstar78/SharpPC-5000 development by creating an account on GitHub.

github.com

 

[smbaker]

for ref,

SharpPC-5000/Sharp_PC-5000_ServiceManual_October1983_compressed.pdf at main · voidstar78/SharpPC-5000

Contribute to voidstar78/SharpPC-5000 development by creating an account on GitHub.

github.com

Let me know if still not high enough resolution - maybe I'll go ahead and tear the binding and scan pages properly.

This is fantastic! Thanks so much, there's theory of operation on the power supply.

Higher resolution on the schematics would be great (if I zoom in they just blur), but this is plenty to get started.

Scott

 

[voidstar78]

Ouch, I see - yea the PDF conversion wrecked the resolution (but now I remember I also had filesize limits on github and had to do the compression).

Ok, so here are the individual 75 pages. Might help a little.

SharpPC-5000/ServiceManual at main · voidstar78/SharpPC-5000

Contribute to voidstar78/SharpPC-5000 development by creating an account on GitHub.

github.com

There are some spelling mistakes here and there in the document - so not sure how final-version it is. But I find the mistakes charming, just a real reminder on the challenges of doing a Japanese to English product translation.

 

[smbaker]

Thanks @voidstar78 for the individual pages, much appreciated.

You have a floppy drive unit too, right? Have you opened that up and taken any pictures? I'm assuming there's a CPU and a ROM inside of it. One of my issues is I have no floppy drive, nor do I have a bubble cartridge with an OS on it (I do have one blank bubble cartridge, and the BASIC ROM is installed, so that's something, if I can get the power supply to work)

Scott

 

[smbaker]

I replaced all of the caps. Only one tested as "definitely bad", but several of them looked sketchy. The first stage of the power supply still doesn't work -- no surprise there. The second stage I haven't evaluated yet.

One thing to note -- two of the capacitors had incorrect polarity marked on the silkscreen on the pcboard. If you're recapping, be sure to note the polarity the capacitor was installed.

 

[voidstar78]

Thanks @voidstar78 for the individual pages, much appreciated.

You have a floppy drive unit too, right? Have you opened that up and taken any pictures? I'm assuming there's a CPU and a ROM inside of it. One of my issues is I have no floppy drive, nor do I have a bubble cartridge with an OS on it (I do have one blank bubble cartridge, and the BASIC ROM is installed, so that's something, if I can get the power supply to work)

Scott

I haven't opened the disk drive yet. Unless it's already broke, I'm reluctant to open up stuff that I only have one copy of.

Are you sure the bubble cartridge is empty? All the ones I've seen (that are officially labeled from Sharp at least) have included the DOS boot content on them (like as part of a ROM in the cartridge - because you can't delete those files either). But once you get PSU going and try it - if that cartridge doesn't work, maybe I can do a "SYS A:" on it ? I can make new bootable disks, maybe that same software can make a cartridge bootable.


The BASIC ROM is misleading. It is needed to run BASIC on the system, but it won't "boot to BASIC" from that alone. I think the BASICEXE.EXE on the bubble cartridges is the BASIC environment (thing to add and edit line numbers and issue RUN, LIST, etc), but the runtime support is in the BASIC ROM cartridge. Different than the IBM PC 5150, where all this was all in one ROM.

 

[smbaker]

Thanks Voidstar. The bubble cartridge I have is NIB. I had assumed it was empty, but I'll plug it in and give it a shot.

I had some limited success -- after recapping the power supply, then opening up the display and removing a shattered capacitor and fussing around with the flex cable a bit, I was able to get it to boot up and give me an error, which as Voidstar suggests, it's because it can't run Basic without DOS. I'm powering it with 6 VDC via the battery connector. I was unable to repair the first stage of the power supply (the part that converts the +15V at the jack to +6V to charge the batter and/or power the secondary supply). It seems like the issue with the first stage is inside of the large rectangular potted component, which is going to be unobtainable. Running it off +6VDC isn't the end of the world, and I may consider tossing in some lithium ion batteries and the appropriate electronics to use them as it would far exeed the original lead acid battery.

The display is very faint though. Is yours very faint, voidstar?

 

[nevergrownup]

Thanks Voidstar. The bubble cartridge I have is NIB. I had assumed it was empty, but I'll plug it in and give it a shot.

I had some limited success -- after recapping the power supply, then opening up the display and removing a shattered capacitor and fussing around with the flex cable a bit, I was able to get it to boot up and give me an error, which as Voidstar suggests, it's because it can't run Basic without DOS. I'm powering it with 6 VDC via the battery connector. I was unable to repair the first stage of the power supply (the part that converts the +15V at the jack to +6V to charge the batter and/or power the secondary supply). It seems like the issue with the first stage is inside of the large rectangular potted component, which is going to be unobtainable. Running it off +6VDC isn't the end of the world, and I may consider tossing in some lithium ion batteries and the appropriate electronics to use them as it would far exeed the original lead acid battery.

The display is very faint though. Is yours very faint, voidstar?

FYI, if you remove the Basic cartridge and boot with no bubble memory plugged in the Sharp will start in store demo mode which includes a basic word processor and general demo stuff.

 

[nevergrownup]

Thanks Voidstar. The bubble cartridge I have is NIB. I had assumed it was empty, but I'll plug it in and give it a shot.

I had some limited success -- after recapping the power supply, then opening up the display and removing a shattered capacitor and fussing around with the flex cable a bit, I was able to get it to boot up and give me an error, which as Voidstar suggests, it's because it can't run Basic without DOS. I'm powering it with 6 VDC via the battery connector. I was unable to repair the first stage of the power supply (the part that converts the +15V at the jack to +6V to charge the batter and/or power the secondary supply). It seems like the issue with the first stage is inside of the large rectangular potted component, which is going to be unobtainable. Running it off +6VDC isn't the end of the world, and I may consider tossing in some lithium ion batteries and the appropriate electronics to use them as it would far exeed the original lead acid battery.

The display is very faint though. Is yours very faint, voidstar?

How much does the brightness control on the side affect the display? Mine will go from no text visible to completely black. Maybe that pot is dirty and not adjusting correctly?

 

[voidstar78]

That's the same error message I get also, if I boot the system without the bubble cartridge (but with the BASIC ROM bottom side cartridge inserted), and try to press ENTER (as prompted) to load BASIC [ and this issue is described in the manual, so it is "normal behavior" ]. As mentioned, remove the bubble cartridge AND all the bottom side cartridge, and see what happens (it should "boot" into a demo-mode built into ROM {this is NOT mentioned in the manuals}). This demo mode doesn't do much, but it actually does have an option to exercise the printer to see how well that works.


As to the screen brightness, I concur with nevergrownup - the knob adjust the screen from a "blank" screen, on up to a nearly fully black. I seem to recall there was a grounding wire on the LCD, inside on the left side (but attached to the case). It's weak and easy to break - and while it may not be essential, something runs in my mind I found that it did influence the stability of the display. [ I feel like this was a wire-braided kind of grounding wire? but I could be mis-remembering ]

EDIT: Also just try different angles. Depending on the room lighting, it's just a very faint display. I think at a "steep angle" it might go better, or just try with more sunlight in the room when you can. If the springs (or whatever they are) for the display are broken, it may be hard to prop it at a good angle. But anyway, the knob should make a noticeable influence onto the brightness.