While I was testing stuff on my MZ-721, a small pop came and then smoke started to rise. I quickly turned off the machine, just in case it is more severe than the power supply. A visual inspection shows that one of the capacitors in the psu is dead (leaking) so it is time for some repair. the tantalum and electrolytic capacitors pass a visual inspection, at least.
Luckily the mainboard looks ok.
I have the service manual, and found the "Repair PSU's" article on the original sharpmz.org.
I will be replacing the dead capacitor and any that looks like it.
Should I do more?
MZ-721 power supply repair
Re: MZ-721 power supply repair
Is that a X2 ?
I had this issue (it is not necessary to work but I dedided to replace while I could only remove it).
https://forum.system-cfg.com/viewtopic. ... 99#p133548 (french language).
I had this issue (it is not necessary to work but I dedided to replace while I could only remove it).
https://forum.system-cfg.com/viewtopic. ... 99#p133548 (french language).
Re: MZ-721 power supply repair
Not sure it is X2 (how do I know?) but it is X class, at least. The schematic only says 0.047 mikroFarad AC 250V. Here are some pictures:
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Torfinn
Torfinn
Re: MZ-721 power supply repair
And C1 (the other filter capacitor) has traces of leakage around it, even if it looks ok. Maybe it has been replaced in the past:
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Torfinn
Torfinn
Re: MZ-721 power supply repair
It's the same as mine. You have a choice: just remove it or replace it with an equivalent one.
It is not necessary as it was just here as a filter which "cleans" the frequencies interferences especially with old CRTs around (so your neighbours may watch their TV set). Nowadays, it is almost useless. It won't prevent your machine from running well.
If you want to replace it, look for .047µF (47nF) - 275V - X2 on eBay: for instance, https://www.ebay.fr/itm/MKP-250V-275V-2 ... :rk:1:pf:0.
It is not necessary as it was just here as a filter which "cleans" the frequencies interferences especially with old CRTs around (so your neighbours may watch their TV set). Nowadays, it is almost useless. It won't prevent your machine from running well.
If you want to replace it, look for .047µF (47nF) - 275V - X2 on eBay: for instance, https://www.ebay.fr/itm/MKP-250V-275V-2 ... :rk:1:pf:0.
Re: MZ-721 power supply repair
Yes, I have ordered new capacitors ( I ordered some for C1 as well) on eBay already. They will get here in some weeks time, hopefully. In the mean time my MZ-700 runs unfiltered
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Torfinn
Torfinn
Re: MZ-721 power supply repair
3 of the 4 MZ700s I have I've had to replace C2... fairly easy job.
Found at:
http://retro-rick.djsho.co.uk
http://retro-rick.djsho.co.uk
Re: MZ-721 power supply repair
Oops, I forgot - I've replaced C2 already. PSU is good as new now
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Torfinn
Torfinn