MZ 80K repair project
MZ 80K repair project
Hi all,
First time posting here.
Hoping you are all well.
I recently aquired a MZ80K with the hope of getting it working, so my students can have a go with using it.
Apart from being filthy, the 'first' problem I have found is that the PSU does not work.
I gave it a quick dusting, then fired it up, intending to check the voltages coming out of it; 2 fuses blew. (bottom right, by the transformer, and top right by the black/red/blue wires)
Upon taking the board out and desoldering the transformer to allow easier access, I found the board was coated in some sticky, tarry substance (not sure what that was...) I managed to get most of that off with alcohol and elbow grease.
I have also replaced all of the electrolytic capacitors apart from the 4 larger ones (which I am having trouble sourcing...)
On that note, this is the closest I can find :
https://www.mouser.co.uk/ProductDetail/ ... 4I1w%3D%3D
But it mentions they are 'Low ESR Electrolytic Capacitors'; I'm not sure what that means...so am unsure whether they would be suitable?
After replacing the other capacitors and blown fuses and cleaning the board up, fired it up and the same fuse (far right by the transformer) keeps blowing straight away.
Any thoughts?
I have noticed there is some sort of deposit on these components, but had assumed it was some sort of glue, could be wrong?
Worst case scenerio, as a temporary measure, has anyone had success using a modern power supply on old equipment like this? Perhaps using similar method to the one described here:
https://www.electronics-tutorials.ws/bl ... upply.html
Looking forward to hearing your suggestions!
First time posting here.
Hoping you are all well.
I recently aquired a MZ80K with the hope of getting it working, so my students can have a go with using it.
Apart from being filthy, the 'first' problem I have found is that the PSU does not work.
I gave it a quick dusting, then fired it up, intending to check the voltages coming out of it; 2 fuses blew. (bottom right, by the transformer, and top right by the black/red/blue wires)
Upon taking the board out and desoldering the transformer to allow easier access, I found the board was coated in some sticky, tarry substance (not sure what that was...) I managed to get most of that off with alcohol and elbow grease.
I have also replaced all of the electrolytic capacitors apart from the 4 larger ones (which I am having trouble sourcing...)
On that note, this is the closest I can find :
https://www.mouser.co.uk/ProductDetail/ ... 4I1w%3D%3D
But it mentions they are 'Low ESR Electrolytic Capacitors'; I'm not sure what that means...so am unsure whether they would be suitable?
After replacing the other capacitors and blown fuses and cleaning the board up, fired it up and the same fuse (far right by the transformer) keeps blowing straight away.
Any thoughts?
I have noticed there is some sort of deposit on these components, but had assumed it was some sort of glue, could be wrong?
Worst case scenerio, as a temporary measure, has anyone had success using a modern power supply on old equipment like this? Perhaps using similar method to the one described here:
https://www.electronics-tutorials.ws/bl ... upply.html
Looking forward to hearing your suggestions!
Re: MZ 80K repair project
I posted your post in FB groups dedictated to SHARP MZs to broaden the scope.
One answer from Melissa Wells for the worst case: "i replaced mine with a meanwell one and it works a treat".
One answer from Melissa Wells for the worst case: "i replaced mine with a meanwell one and it works a treat".
Re: MZ 80K repair project
May I suggest to check if there is no short-circuit due to the motherboard when powering the machine on. Unless you tried it without the motherboard to make sure it is an issue from the PSU.
Re: MZ 80K repair project
Thanks for your reply, and also for passing it onto others
It is great news that others have had success using modern power supplies to run these computers; very promising.
My first action when opening the case was to isolate and remove the powersupply. I got that idea from a very good youtube tutorial where the creator found that the voltages were way off due to warn out capacitors. With mine however I get no voltages at all onces the fuse blows
Re: MZ 80K repair project
Ok. I also think they are glues in the last photo.
Re: MZ 80K repair project
https://original.sharpmz.org/mz-80k/download/sm80k.pdf
Look at page 36, 37 or rather 38 if your PSU is a UK version.
So F101 and F401 blew. By replacing them, only F101 blew.
Honestly your first photo is too small to spot something wrong. You should make a higher resolution of it.
Alos from page 12, you have the steps to check for the PSU.
Look at page 36, 37 or rather 38 if your PSU is a UK version.
So F101 and F401 blew. By replacing them, only F101 blew.
Honestly your first photo is too small to spot something wrong. You should make a higher resolution of it.
Alos from page 12, you have the steps to check for the PSU.
Re: MZ 80K repair project
Thanks for the link to that file. Looks very interesting.
Here are links to the original resolution images already posted :
https://drive.google.com/file/d/15zwgyC ... sp=sharing
https://drive.google.com/file/d/163l0Qx ... sp=sharing
https://drive.google.com/file/d/16130gS ... sp=sharing
This is an image of the back of the board : https://drive.google.com/file/d/1699NaC ... sp=sharing
This is the full board from a different angle : https://drive.google.com/file/d/167Xypi ... sp=sharing
Here are links to the original resolution images already posted :
https://drive.google.com/file/d/15zwgyC ... sp=sharing
https://drive.google.com/file/d/163l0Qx ... sp=sharing
https://drive.google.com/file/d/16130gS ... sp=sharing
This is an image of the back of the board : https://drive.google.com/file/d/1699NaC ... sp=sharing
This is the full board from a different angle : https://drive.google.com/file/d/167Xypi ... sp=sharing
Re: MZ 80K repair project
In all honesty, your board looks clean, much cleaner than the MZ-700 I had to repair once.
Back of the board: I can see some scratches but not sure they are an issue. It doesn't look you have cold soldering points but I'm not a good judge.
Full board from a different viewpoint: The only dirty spot I can see is at the bottom of the big blue cap.
Interesting enough, several researches about MZ-80 K PSU failures are related to tantalum caps (four blue ones) issues. Here is one link: https://www.nightfallcrew.com/13/01/201 ... ly-repair/.
And beware, the board is a little different because I think yours is a UK version.
Back of the board: I can see some scratches but not sure they are an issue. It doesn't look you have cold soldering points but I'm not a good judge.
Full board from a different viewpoint: The only dirty spot I can see is at the bottom of the big blue cap.
Interesting enough, several researches about MZ-80 K PSU failures are related to tantalum caps (four blue ones) issues. Here is one link: https://www.nightfallcrew.com/13/01/201 ... ly-repair/.
And beware, the board is a little different because I think yours is a UK version.
Re: MZ 80K repair project
Check that capacitors C407 c406 c503 or c504 are OK.
I can remember repairing a K power supply (that kept blowing fuses ) for MH in Weymouth many years ago by replacing the blue capacitors which are part of the voltage setting circuit. I think one was short circuited but we replaced all 4.
ESR is short for Equivalent Series Resistance.
All PS that power computer equipment are low ESR
Search for PSs with 4 output voltages +/- 12V and +/-5V and ignore the –12V if you need a new replacement unit.
I can remember repairing a K power supply (that kept blowing fuses ) for MH in Weymouth many years ago by replacing the blue capacitors which are part of the voltage setting circuit. I think one was short circuited but we replaced all 4.
ESR is short for Equivalent Series Resistance.
All PS that power computer equipment are low ESR
Search for PSs with 4 output voltages +/- 12V and +/-5V and ignore the –12V if you need a new replacement unit.
Re: MZ 80K repair project
If I look at the schematics correctly, fuse near cables you are talking about is F401, on the +12v rail. Did it blow *after* you removed it from mainboard? Because there is not much there to cause it when it's not connected to anything.
That gunk is probably just kind of glue used during assembly/soldering.. or whatever was left from anti-vibration silicone/glue
Leaked caps are much more... gross
*edit*
And +12V rail is used only in display unit. So you might have to look for shorts there.
That gunk is probably just kind of glue used during assembly/soldering.. or whatever was left from anti-vibration silicone/glue
Leaked caps are much more... gross
*edit*
And +12V rail is used only in display unit. So you might have to look for shorts there.