Casio FZ-10M fails to start/freezes—only screen & LEDs light

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db0451
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Casio FZ-10M fails to start/freezes—only screen & LEDs light

Post by db0451 » Wed Dec 10, 2014 9:45 pm

Hello all. Halp!

I’m looking for advice from owners of the Casio FZ-10M (a.k.a. Casio FZ-20M and Hohner HS-1/E) rack-mounted sampling synth module – or its keyboard-equipped sibling the FZ-1 (HS-1) as that might also be applicable in this case.

I bought an FZ-10M, which that needs repair: specifically, it does not start/boot fully , only showing a screen light and (sometimes) 2 red LEDs, then seemingly freezing that way indefinitely.

I have little in the way of diagnostic equipment but am happy to try if I get plausible suggestions. The service manual for the FZ-1 only describes the diagnostic program IF it loads in the first place, but I don’t even seem to get that far!

I doubt it’s just the (infamous) LCD screen, but to check, how would I go about testing for any response using buttons or sound, without being able to see what the screen says? Anything simple that will produce a sound or change some LEDs if the whole thing isn’t busted is what I need.

Otherwise, hopefully someone knows the described pattern of failure, and can suggest what needs replaced, tested, etc.

Thanks in advance. I really hope I can get this fixed and get those filters blasting! :)

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by madtheory » Thu Dec 11, 2014 10:37 am

If it's not seeing the floppy drive, then that's where you need to look (i/o circuitry for that) but you'd need a scope to check logic levels etc. Might be corrupted boot ROM too. Is that a PROM of some kind? Is the code downloadable?

Best case is it's just a faulty floppy, in which case replace with HxC emulator, which you would do anyway :)

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Thu Dec 11, 2014 12:33 pm

Thanks for the reply!

A failed floppy drive controller is an interesting idea, but it assumes the FZ always tries to check the FD when booting. The OS itself is on ROM, as you also know, and I believe loading other programs is done via a menu in the main OS, rather than by booting with a totally new OS. And I would assume any FD check would happen at a time when enough of the OS was loaded to display text, etc.

Suggesting the ROMs themselves might be corrupted – the horror! :P Yeah, these are EPROM-looking things, but the kicker is they are soldered directly in (not socketed). Worse, there are no images of the firmware floating around that I know of (only the FZ-1).

The only other thing is the big capacitor on the PSU has some odd looking gunk at its base on the board – maybe just epoxy or similar, but maybe an issue? Perhaps it has hosed one of the v-reg outputs or something; there is one right next to it. If anyone has experience and knows where to check for particular voltages, that would be excellent. Also, a photo of someone else's FZ-10M/-20M power boards would be useful, to check how that capacitor should look.

Someone else suggested trying to change the screen’s contrast, but no dice: just the same behaviour of only the backlight and sometimes a red LED or two below it. This screen probably works on its own… I have an HS-2/E, so in theory I could swap the screens to test, but I'd prefer not to have another rack unit open right now!

Thanks again for all ideas.

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by madtheory » Thu Dec 11, 2014 7:20 pm

Have you not found the service manual? If the gunk is sticky then replace the caps. Ya EPROMs do get corrupted sometimes- horror! :)

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Thu Dec 11, 2014 10:10 pm

Only found the service manual for the FZ-1, but I assume it is largely applicable to the FZ-10M. It does not mention anything about a (possibly) dodgy FD causing total failure during boot. It mentions typical ROM/RAM checks but indicates that even if the fail, there should be some sort of repeatable indication on the LCD. But obviously that does not account for ROMs possibly (but hopefully not) being so badly corrupted they can’t even begin the check…

Does anyone have a dump of these ROMs? In both my unit and the only other one I have found detailed photos of, they are labelled MZ1A and MZ1B. Once again, I feel a need to shell out £100+ on a proper ROM-reader and take rips of absolutely every device I own, in case they just die one day without any way to restore them… :o

Anyway, I guess the most plausible thing to do first is to determine test points and get the voltmeter involved. Not an enviable task, with that unbelievably huge transformer just sitting there, possibly not working quite as it should… :shock:

I found the old page on DanceTech, with hundreds of people asking questions and no one answering them… and there were a few posts by people who seemingly also experienced some kind of failure to boot, but sadly/unsurprisingly no solutions.

I also found a thread somewhere else where someone had posted photos (mentioned above) of boards including the PSU, and the caps on theirs seemed to be gunky at the base too; so, either that was an intentional anchor of some sort by the designers, or that other person’s caps were (also) nearly-but-not-quite broken.

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Sat Dec 13, 2014 12:42 am

In the context of avoiding wear by removing disks, I read someone saying that the FDD is one of those awful ones that will always spin as long as there is a disk in it (and why did ZIP drives have to inherit that? I thought they were meant to be better than FDs!).

Well, here was a start: The FDD in this FZ-10M does not spin when a disk is put in, nor does it light up or make any detectable acknowledgement of its existence. (Perhaps interestingly, maybe not: a muting relay does click on and off, although that might be totally automated by voltages without requiring any ICs to be working…?)

Checking the cable going into the back of the FDD, I found that although the +5 V supply is present, the +12 V is not: I get a constant 0.05 V instead, even if the FZ-10M is powered off(!?)

This missing +12 V supply seems to trace back to the voltage across the pins of an electrolytic cap on the PSU, with values 15 V and 470 pF. The first step is, of course, to check the voltage over that, to make sure it’s not just the wire to the FDD that is broken somewhere along the way (which would not explain the overall failure). However, there’s no way I’m going to turn on that gigantic transformer and then fumble around with voltmeter probes on my own! So, testing that capacitor will have to wait until I can get someone to operate the power button for me. :idea:

This +ve supply, via bunch of other baffling (to me) electronics, seems eventually to originate at an IC that apparently is a “S1WBA10 NTE Equivalent NTE5332 BRIDGE RECTIFIER”, which also serves some other voltages/parts of the PSU. Because it is not only the FDD that is broken, I wonder whether this rectifier, or some other multi-purpose part of the PSU, is hosed – and downstream supplies with it. However, the diagram implies that the +5 V supply for the FDD might also connect to that rectifier, and the +5 V works, as does the EL inverter, so…

Anyway, if anyone knows what this rectifier should be doing, and how I can test it to determine whether the problem is it – or any more plausible node on the PSU – please do let me know.

All other suggestions are, as always, gladly welcomed. Thanks!


[edit] S1WBA10 is preceded by the fuse F4. I guess I should locate a replacement for that, just to be safe. [/edit]

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by madtheory » Sat Dec 13, 2014 3:29 pm

Replace the 470mF cap. Easy to do. The voltage rating of the replacement needs to be at least 15V, a higher value is ok. Assuming this is the one with gunk on it? You're over worried about the trafo. Just stay away from the input side and you're ok. Are you going to put a hxc in there if you get the floppy running?

Nice sampler :)

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Sat Dec 13, 2014 4:29 pm

Nah, this cap is 470 uF, smaller, and gunk-free. Seeing as the gunk is confined to the larger ones, I’m now confident it’s a sort of glue – to function as a strain-relief to protect the solder joints, etc.

I would gladly replace any electrolytics later, but that would require taking the PSU out altogether. In contrast, I would prefer to have it screwed in and operable for the moment, so I could take educated advice on what to test with a voltmeter – with the option of plugging in main boards and probing those, too.

I still need to test the cap in question – betting it’s not got a voltage over it, and the problem is likely to be earlier in the PSU. Thanks for the reassurance about the transformer, haha; my reluctance is amusing, seeing as there have been many occasions in the past where I’ve ignored electrical safety with wild abandon! But I think my cut-off for that is at about 30 V, then I start to worry. :P

This will indeed be a great sampler if (when?) I get it working. I envision it being used really as a synth with user-definable waveshapes, and of course for ridiculous filtered drums. :D

As for the floppy drive, I used to replace those as a priority, but I might hold off for a bit, especially if it needs a special interface. Even the generic 34-pin+USB+FAT32 ones are still about £30 after P&P, which is totally fantastic compared to a year or two ago, but it means less money to buy actual synths! :ugeek: An HxC is something I’ve wanted for a while in general, though – or several, to be precise… In my other gear that supports sysex, I’m nowadays happy to leave the old FDD – but convenient disks are especially important in samplers, of course.
Last edited by db0451 on Sat Dec 13, 2014 5:05 pm, edited 1 time in total.

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Sat Dec 13, 2014 4:47 pm

Hmm, voltage across capacitor is the same as at the FDD: -0.15 V instead of +12 V… Where do I look next? Power supplies almost completely baffle me, although I’m very keen to learn.

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Sat Dec 13, 2014 6:47 pm

quoting myself at GS:
Yeah, checking voltages so far, I still have only one thing missing:
Image
But I doubt that FD +12 V can be holding up the rest of the system; I managed to get the FDD to make disgruntled noises by feeding it power hijacked from a PC, and the FZ didn’t care either way.

Nonetheless, I’d like to ‘walk back’ from that cap (with the voltmeter) to determine whether anything more serious/early than an electrolytic is broken here. Does this sound plausible, and if so, would you be able to suggest what/how to probe? Thanks.

Also, very good point about the RES line [CPU/system reset, active low]; I’ll check that next. It does seem to trace back to the S1WBA10 rectifier that also sources the failed +12 V… :-O

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by sneakthief » Sat Dec 13, 2014 6:50 pm

NB re. "Nah, this cap is 470 uF" - sometimes people write microfarads as mF instead of uF or µF
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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Sat Dec 13, 2014 7:01 pm

Thanks for the info, but then what about milliFarads? :P Searching suggests those are not used often to cite values, but I still like to avoid ambiguity wherever possible. The tutor who taught me about SI units made sure of that. ;)

intriguing: CPU RES line seems to hover around 0.12 V, whereas being active low, I assume it is meant to bounce up to +5 V a few seconds after power-on.

Next thing is to test the h**l out of that S1W rectifier – because both the missing +12 V FD power and /RES signals eventually trace back to there. For someone who, as is obvious, is very new to these sorts of diagnostics and circuits… how would I go about testing a rectifier? Datasheet first, of course… off to Google I go.

[edit] OK, the +/v terminals of the rectifier are at +19.8 V. Sounds plausible? Need to figure out where it goes wrong after that, then. [/edit]

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Sun Dec 14, 2014 12:46 am

I might have traced the lack of +12 V to the voltage regulator in that line. I say “might” because I sometimes got readings from it on my voltmeter, sometimes not at all. This might have been purely because it is so flipping hard to reach with the probes. It must finally have shorted as I saw a nice big white spark between its legs (ooh-er, missus), and then it was gone. That short seems to have cascaded backwards (is that even possible?) because now I have a blown fuse F4, which serves the aforementioned rectifier S1WBA10. So, now I have no +12 V or /RES! However, I seem to recall /RES was back to running properly at +5 V some time before the fuse blew… I don’t know; it’s all blurring together.

As you can see, I need to stop this for a while and have a sleep. On the plus side, I didn’t die. I guess? That’s probably a good thing.

/RES is/was presumably the real issue here; credit to acreil at GS for noticing that as it might have taken me ages to realise. So, the next steps are to replace that fuse, hang some wires off that vreg to test it safely… and learn the dark art of transistors, I suppose.

I replaced several electrolytic capacitors while I was at it, which might improve my odds once the fuse is repaired, but me tell you: the PSU was not made for easy servicing, as without cutting some of the main wires, you can only balance it on its side (via the heatsink) and sort of poke at it horizontally with the soldering iron. :? The same applies to the main board, by the way, which just has to chill on its side at the back of the chassis. :? :?

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by madtheory » Mon Dec 15, 2014 12:46 am

db0451 wrote:The tutor who taught me about SI units made sure of that. ;)
Tutor obviously never worked on anything from the sixties (I learned that lesson the hard way). Ya I know I was technically incorrect (and I beat SI units into my students too) but in my defence, if we were face to face it would be understood.
db0451 wrote:That short seems to have cascaded backwards (is that even possible?)
Yes, it's a short. The thing drew more current. There's no cascade. Remember Kirchoff?

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Re: Casio FZ-10M fails to start/freezes—only screen & LEDs l

Post by db0451 » Tue Dec 16, 2014 1:01 am

madtheory wrote:Ya I know I was technically incorrect (and I beat SI units into my students too) but in my defence, if we were face to face it would be understood.
It apparently seemed like I was being more critical of the unit than I really was :-)
Yes, it's a short. The thing drew more current. There's no cascade. Remember Kirchoff?
Heh. Electronics is not my specialty, as is probably obvious! Not gotten around to Kirchoff yet. :-P "Cascade" was just a bad choice of word. The rationale for the fuse being blown by a downstream draw was explained to me earlier today, and like most things, is embarrassingly obvious in retrospect! :lol: Thanks for confirming.

New fuse (1.0 A instead of 0.8 A, but oh well - the service manual quotes 0.8 but with a part # that implies 1.0) and vreg/transistor are on the way. If I don't get anywhere fast after that, I think I'll try to transplant a PSU from a similar old machine or a hacked ATX.

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