PaoloB

Hi All, Update on the power brick. Today I replaced the big capacitor (in case, be careful, always discharge it before touching its pins) with a “new, bigger, better” one (of course: same capacitance). No surprise, though. Output voltage is still around 18 V with 220 V nominal input (in fact, the original capacitor looks just fine, no bulging, no leaking whatsoever). MZ-1 units work. However, what indeed puzzles me is that under load the output voltage drops just slightly, down to some 16 V. Way much above the indicated, and - I’d assume - expected 10.5 V, plus minus. If plugged into a 120 V outlet, you get in between 8 and 9 volts. Sufficient to power up the minidisc unit, but not to operate it (e.g. eject would not work). So, it’s not even a “universal” power brick of some kind just differently labeled depending on the plug and final market of destination. Would be interesting to know the actual range of voltages the unit can handle...

Just swapped the fuse with a good one taken from a donor board (damaged unit). Must say I missed the caveat about the solder temperature and used 260 deg C. Luckily, it seems as though I did not damage the fuse, so the unit is alive again. As for the power brick, I will in any case replace the capacitor with a new one: I’m sure the old one is OK (can’t measure it, though), but you never know. I attach a picture of the fuse for future reference. Thanks again for your support, I’m really grateful I could learn something new. Paolo

I just made a quick and dirty check by bridging the fuse and... it just works! Any suggestion on where to source an exact spare or equivalent? Even though some web links are suggesting that Sony 1-533-282-21 is a 2A/72V, the unit is reading a “50” on the small case, suggesting - maybe - 5A (which seems a tad overrated)... Thanks!

Hello, It seems you got it right! By a quick continuity check, PS401 seems to be open on the faulty unit. Will try to replace it by desoldering a good one from a donor board, I will keep you posted about the progress. Thanks!

Hello, thanks indeed for the feedback. Yes, it’s one of those power brick with a transformer (220 V). Didn’t consider the actual voltage goes with the load... So, it must be something different. I tried swapping both boards with known working ones from a donor unit and it came back to life (with a bench power supply), albeit with a disc error message (different calibrations?). What is puzzling me is that a good unit draws some 10 mA even when off. The faulty one does not, indeed stone cold (0 mA). That’s why I suspect something is fried. Additional point. The faulty unit had an original Ni-Cd battery pack in, which used to keep some faint charge. But now is totally dead. Maybe something went wrong as the battery failed.

Hi Guys, I have this MZ-1 unit which I fixed some time ago (eject). I haven’t touched it for a while, but unfortunately I forgot it permanently connected to a plugged original power supply. A couple of days ago I tried to play some stuff, but the unit is now totally dead. So I checked the output of the power supply and to my surprise, the output was around 18 V vs nominal 10.5 V. The power supply itself is indeed basic, I would say the only component that might have failed is the big capacitor, I will replace it and check again. Anyhow, whatever the issue behind, I would say that almost certainly the totally wrong voltage has fried some chips nearby the power connector on the analog board. As I’m no electronic engineer, but I’d speculate some voltage regulators are cooked... I’m not quite sure I’m willing to go for a debugging session back to back with a working unit, so I was just wondering if any of you has had the same unfortunate accident and, in case, has any suggestion to share. Thanks in advance for the feedback. Paolo

Maybe “brazed” is not technically most correct, maybe “soldered” is the right word. Anyhow, what I want to highlight is that the combined gears are not supplied in one piece, but they are two elements combined together. I considered various options, best one would have been friction welding, to keep the gears clean an neat, but impossible, at least for me. Some kind of glue might have worked too, but eventually I opted for soldering the elements together, using, in fact, solder. Concerning the OP, I will try to swap components with working units, just to narrow down the area of investigation, will then go through your checklist. Thanks. One question, if I may. I noticed that one unit tends to slightly scratch the disc surface during recording, or at least this is what I believe I see. Recording is otherwise OK. So, here I assume the magnetic head is calibrated too low and is too aggressive on the surface. Is there any procedure for adjusting the height?

Hi Guys, some update on my last repair. Unfortunately, after fixing the loading mechanism, the unit is still not working. Disc is loaded, but seems to me that the optical pick up is dead, as the disc is not recognized during the TOC reading (“DISC ERROR” - pick up is not moving, but if you manually move it, it does go back to initial state upon disc insertion, so it’s not the motor). Unit is a poor purchase on eBay, didn’t put much attention to the pictures and bought it for dirt cheap. Unfortunately, the unit is quite battered, chassis dented, missing “edit” slider, “rec” one is broken. One disc stuck inside, when I pull it out, the surface was visibly and badly scratched, like if someone tried to make lever with a screwdriver or what. So, probably it was not so “I don’t know, never touched” as promised. Amen... Back to the optics, I have reason to believe that someone tried to disassemble the unit for ejecting the disk, but did not shorted the pick up lead before disconnecting it and just blew it. Any opinion / suggestion in this regard? Anyhow, the unit seems to be an early one, logic board sn is 1-645-916-11, whereas the other two units I have are rev 12. On this one there’s an awful lot of hard wiring and some small boards patched on the main ones.

Here are some details

As I just fixed another unit, I’m sharing a couple of pictures showing the gears and the assembly.

Hello, the supplier is http://www.kkpmo.com . Quite clearly, you will not find 1:1 replacements, but you can order custom made spur gears. When you combine together the gears (special glue / brazing) and use proper shaft sleeves as spacers, you can get a perfect replacement for worn out or broken gears. In my unit I had missing cogs on midway gears B and C 4-955-496/7, I replaced them with metal gears (brass). Module is M0.3. I have now ordered some spares for a D-Z555 unit with stuck sled. In that case M0.25.

Hi guys, should anyone still be interested in this thread, I have managed to source equivalent spur gears for fixing the infamous issue with the MZ-1 no longer ejecting disks. Just fixed mine for super cheap money. Not for the faint of heart, but doable.