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MDS-JE530 does not record, OWH is tested and OK

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Greetings to everyone - I am a newbie here, though not new to Minidisc. I entered the MD world in about '96-97, when I bought my MZ-R3 in a Duty-Free shop at London Heathrow, while waiting for connection. It was an amazing piece of kit that time, and I must say, the MD technology is still a fantastic engineering achievement in my eyes.

I have been reading the forums since about two months now, mostly seeking for repair tips - having a couple units I bought recently second hand (mostly fairly cheap), with the intention of bringing them back to life and preserve. And, already a big "thank you" for the forum - I already managed to fix my MDS-JE510 unit, that did not accept discs, ejecting all with C13 error. Following Jim Hoggarth's instructions, I turned it back to fully functional, and it still holds since then.

Now, I am in a project of repairing the unit in the subject. I tried a couple of things but still not yet there. This 530 arrived with a broken OWH (Overwrite head), that had clear signs of previous failed repair attempts, thus the machine was play only, but otherwise working OK. As a first step, I took a 100% OK OWH from a fully functional 520 unit, built it into the 530, but then the 530 still did not record, i.e., when ejecting after a record session, the disc remained blank. Testing the same OWH back in the 520: all OK. (BTW, I finally fixed that broken OWH from the 530, tried also in the 520, and the 520 just can record properly with this repaired one.) Error history in Error Display Mode shows E04 and E09 alternating ("Address cannot be read" and "Playback retry error" respectively).

Then I took the service manual and began performing the checks (except for laser power and traverse signal, as my old oscilloscope gave up recently), and the only error I could find  is a "7350" error in self-recording (and focus bias) check, obviously, as no data was written to the disc. Apart from that, the deck seems all fine, functioning as it has to. Having the idea the focus could be out of range, first I created a continuously recorded test disc in a spotless 330 unit, then put it back to the 530, and checked the focus bias with that. It went all OK, continuous play test showed all error rates below factory specs. Repeating the same procedure with a continuously recorded disc made with the 530, I got back to the "7350" error - as nothing was written on the disc.

I am stuck here, I have no idea, why the unit is not recording, as everything seems OK. This particular deck run only 38 hours of recording, and 418 hours of playback, and looks like new - would be great to have it fully functional again, especially for the Type-R ATRAC.

The schematics of the OWH drive circuit is fairly simple, pairs of diodes and transistors, plus a capacitive coupling to the writing coil - all these parts look robust on the BD board, I cannot even imagine they blew (or the IC driving the transistors?). I could only check the diodes, they seem to be OK, however, I have no means to check these special transistors. As soon as I can get my hands on another oscilloscope, will check the writing signals on a good unit, and compare with the 530, to see ho far the signal gets, and when it stops.

But before that, if anybody with some experience can give me their view, whether I am going the right direction, or something else needs to be checked/adjusted. I am aware, that the time I will probably spend on fixing this may not worth it, and I may buy another unit at a lesser cost, but hey, this is a hobby, and I looked for some challenge :-) . Should I not succeed, I will put up the unit for parts, if it can help others to fix theirs.

Thank you in advance and apologies for the fairly long post.

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You don't need the OWH to do actual recording. Many folks have reported everything working fine for many minutes and then they simply get a blank disk. Having no overwrite means that you never get to record the TOC. If you can see the seconds clicking off on the display then all should be OK except the OWH. If you don't see that, then, perhaps strangely to you, the OWH is not your problem. There's nothing to adjust on the OW circuit if my memory serves me.

I'm wondering if the abuse to the machine was it being plugged into the wrong mains power. Even 120 vs 100 makes a difference on Japan-intended units. Will this give you a clue to what is wrong? You can check all the relevant voltage levels. I'm also wondering about the write protect circuit not doing the proper thing, you may need to check the signals from the microswitch which controls whether writing is disabled - maybe it's (physically or electronically) "stuck" and somehow the OW never gets enabled.

I don't know where 7350 is coming from, can you give us a better locus for this error number? I cannot get the bits in the "retry cause display mode to make anything like this", so I am probably merely demonstrating that I've never worked with this feature. Either 73 or 50 could be a track number (in Hex). Tell us all the digits you see on the display, and try to figure out (Page 9) what they mean.

Sounds like you're hot on the trail. Maybe we'll be getting you to fix our equipment soon!

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Thanks for your reply. These days are kinda busy, I hope I can continue working on this deck at the weekend, and hopefully sometime next week I will possess a scope too. In the meantime, answering you I added some more details. As soon as I  can have my hands again on the machine, I will report here where I am  progressing with the repair.

"I'm wondering if the abuse to the machine was it being plugged into the wrong mains power."
The deck is a European version, was also originally purchased over here (mainland, 230V across, fairly flat), so such a change in mains voltage should not be an issue, unless the machine has got a spike or shock earlier, that hit some recording related parts. I will check all individual power rails' voltages at more points to exclude this possibility - already measured the supply voltage lines on the ribbon cables, all seemed to be in order.

"If you can see the seconds clicking off on the display then all should be OK except the OWH."
That's right, when in recording mode, seconds were clicking just as if there was no problem at all.

"Having no overwrite means that you never get to record the TOC"
And, that actual magnetic polarizing does not happen during recording/writing, only the laser heats and erases the bits.
I made two experiments: first I took an earlier recorded disc with several tracks on it, put into this 530, erased one letter of the title to make a change to the TOC. Upon ejecting and reinserting the disc, it showed "blank disc" (I certainly restored my test disc cloning back its TOC I saved prior probing).
Then I made a short recording on a brand new, never used blank disc. The result was a blank disc. Then cloned a matching TOC onto this disc in another deck. While cloning was successful, I could not play back the disc - the drive was audibly seeking back and forth, and the time display did not progress.
These results told me, that the OWH did not function for some reason (though the head itself was operable, proven in another deck), and rest of the machine seemed to be OK.

"There's nothing to adjust on the OW circuit"
This is an important piece of information for me. At the end of the day, this was my assumption too.
I thought whether there was something to adjust on the OWH/OP relative positions and focus, but probably there is nothing there either, as the OWH is mounted at a predefined position on the OP arm, and the writing coil covers a fairly large area, way larger than the tip of the focused laser beam. The focus of the laser then might not be an issue, if the drive can read both kind of discs properly.

"check the signals from the microswitch which controls whether writing is disabled - maybe it's (physically or electronically) "stuck" and somehow the OW never gets enabled."
That's a good point - learning from the issues with the 510, I already took the switch panel off, and checked all switches, but found no problem there. However, I cannot yet measure, whether the control IC's relevant input circuitries are in good order or not. Once I attempted to fix an S38 that did not respond to any of the front panel buttons, then it turned out, that two of the key matrix inputs on the main IC were dead, i.e., internally shortcut to ground. I hope it is not the case now, because then no way to repair it (frugally, I mean).

"I don't know where 7350 is coming from, can you give us a better locus for this error number?"
7350 is displayed as a C1 error in self recording/playback check, while this value must be <80. The same time, ADER is 0, and that is a good value. A Sony technician wrote once somewhere on the net (I keep re-searching for the link), that C1=7350 means "does not read correctly". It is then not an error code, but rather a bad value of an error variable. Will take a photo, when I am back to playing with this deck, how it is displayed.

So much for now, I will get back soon. Thanks again for the care and the ideas.

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It must be the actual connection to the OWH then. The normal thing that happens is the cable gets an invisible crack in it somewhere it was flexing. However as you mention that this head worked ok in another machine, may I venture to suggest that it (the break in continuity)'s upstream from whatever you fitted. Especially since you said a working OWH failed in the exact same way when removed from another machine and transplanted here.

Look at printed page 40 (on page 36 of the pdf). Top right. The connections to the OWH are pretty simple. If the ATRAC chip isn't actually blown up (game over), the answer must lie in that little piece of the diagram. What's BG1? some kind of isolating crystal or something? And you've got 4 test points to check, too, TP320,1,2,3

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BG1 is a solder joint. Sony has them at many places, it is part of the EDS protection during repair. Normally, one has to remove the solder (thus disconnect the two parts of the circuitry) before replacing the OWH, then resolder afterwards.

Next time I want to check the signals on the output of the bridge at those test points, then the inputs of the logic IC, the two signals coming from the ATRAC: "EFMO" (at TP307) and SCTX (at TP301). I cross my fingers, these last two will be alive, should any or both not, then yes, game over.

I can hardly wait for having an oscilloscope, at this point a simple DVM is not enough for such tests.

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A little disappointing day...

I could play a few hours with the 530. A 520 was the reference unit, I repeated every measurement on both machines. The OWH signals look alike on both BD-s, both OWH circuitries seem to be working OK. Still, no recording made on the 530.

I began pulling my hair out. OWH OK, BD OK, I even swapped spindle  motors, still the unit does not write to the disc. It's very late now (actually, getting very early), so I stopped for now, looks I can't see the forest for the trees.

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Looks like no laser power to the optical head, then. It plays, so presumably what's happened is that the higher power required for writing is either busted or adjusted to a low value. Reading only takes 1/10 of the power (usually 0.7mW as opposed to about 7 mW).

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Yes, something is not round there. If I understand correctly, there is a single laser diode, that does both writing and reading, the difference is in the applied laser power. Therefore, hopefully, with proper settings, it can write again.

Without a laser power meter, I could not yet check it, all I can see is the settings all seem to be in range, i.e., IOP value matches what is on the OP's label, and other laser power settings match proportionally two other units' that I could compare to.

It then probaly lies with the control circuitry, that switches between high and low power. Or, worse, it could be, that the laser itself is aged (odometers don't reflect this though) - I saw a similar situation, when a DVD-recorder deck "forgot" recording, ejecting discs with error, though it was still able reading dvd-s.

Seems I need to develop a DIY laser power meter, because the generic equipment are very expensive, the Sony gear is very seldom (just missed one on ebay a month ago, it was up for a few minutes only, fixed price 45usd or so ...), to see exactly, what is the laser emission in recording mode, on the surface of the disc. This would help to decide, whether to continue working on this unit, or just scrap it for parts.

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Up to now I have seen more trouble with misadjusted reading power than writing power. The major thing that can happen is too much write power may burn the pickup out... but that surely is not happening here. Or it would not read. A common failure seems to be that misadjusted reading power makes it look as if writing failed. It's time to replace the pickup maybe. I like your theory of the switching circuit. Can you actually do the IOP current measurement?

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Lacking an LPM, for further tests I decided to make some trial and error settings, though within a ~20% range of the original values, not to risk burning something. I found that increasing the writing power of the laser has no impact until a certain point (at around 10-15% increase), i.e., recording looks going OK, seconds ticking, but the result is a blank disc (if attempted to record on a blank disc). Going slightly above changes the situation: during recording, the display begins counting the seconds, then after a few moments it displays "Retry". Though the result is still no recording made, the retry error should mean something - I tend (or hope ...) to believe, it is only a settings issue and not a broken component, but cannot obviously justify without the LPM.

I took a look at the link above (thanks anyway), but this meter is not applicable for my purpose, for a couple of reasons. First, it is only working in the 800...1600 nm wavelength range, at given discrete values (MD lasers work at 780 nm). The measurement range is up to 6 dBm only, that is, slightly below 4 mW (we would need up to 9 mW or so). Last but not least, the problem is the probe. This tester is designed to measure fibre optics' laser power, thus the "probe" is built inside the unit (and cables to test are connected to the meter).

I am in the progress of designing and building a low cost probe, that can be attached to a DVM or DMM, and then make a simple mV to mW conversion. Calibration is still a question mark though, but I expect to have some fair results by using an intact, working deck's values. As soon as I have reasonable progress, will publish it here. Besides this, I am about to post some other fixes and mods to other machines I made in the meantime, if that can help others.

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Yes, the Sanwa LP1 (for example) is a great piece of kit, it has a range of 400...1100 nm, and also has a conversion table, to multiply the shown figure as you mentioned, for the given wavelength.

I saw a few pieces on ebay at around 200 bucks, that is a great price, if one would use it regularly, but for that money I could buy 4-5 MD decks :-) .

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Finally, my homebrew laser power meter is put together. It cost $3 worth of surface mount components, a used disc sacrificed for the shell, a piece of pcb, and some other stuff I found in the back of my drawer. Initially I tested it with my digital multimeter hooked on those test terminals, but then I found this neat little five-digit Volt-meter I bought some time ago on ebay, I think it was five bucks or so with free shipping from China.

Without much fine tuning, I popped this little probe into all the decks I had at hand, and measured the laser power. From the mV readings and the nominal laser power values I calculated the mV-to-mW multipliers, and I took the average of a unit I trusted the most, a 940. Using this sole multiplier as the "calibration", I recalculated the measured mW figures and compared to the factory recommended range. Most of the other units were nicely within specification, but this 530 in question, that immediately popped out, being near 40% below the necessary values, i.e., 0,55 mW and 4,32 mW versus 0,9 mW and 7,0 mW respectively.

Now, it might be that easy, but before changing anything, I want to check the IOP, to see, whether that meets the specs, and set the measured value for further adjustments. For this I will need that rig connecting to the drive, currently waiting for the  special connector to arrive.

So much for now, I will update the thread as I progress. Some photos attached below, just for fun.

 

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A little (for me actually a big) success tonight.

The mini wire-to-board plug arrived from China at last, and I could not wait to improvise the jig for measuring IOP.

My LPM probe popped into the deck, jig attached to BD, DVM hooked on the jig, and there I began setting the laser. It was not that straightforward as I expected, because either the mW or the mA value fell out of the desired range.

I suspect this OP underwent some improper settings in the past that wore it more than the odometers would show, as I could not fully turn the laser power up in writing mode. Nevertheless, I could set it very close to the minimum value stated in the service manual. IOP was also slightly below the -10% limit (but within the -10 mA limit, stated also in the SM somewhat contradictory, or at least inconsistently). Interestingly, read mode laser power did not need any adjustment, it was spot on.

Quick check of other variables, i.e., FBIAS, CPLAY, CREC, etc. (traverse check maybe at the weekend, if I can have some more relaxed time), then I inserted a recordable MD, and hit the RECORD button. No RETRY error, seconds ticking, so far so good. Could not hold my breath for more than 10 seconds, hit stop and play.

The 530 does record now!

Eject, TOC writing, pop back in again, play - recorded material is there and playing back properly.

I am happy that I could bring back this nice unit from read-only, also, it was a great excercise.
Thanks for the support and the hints/ideas.

 

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On 02/04/2016 at 12:41 AM, NGY said:

The mini wire-to-board plug arrived from China at last, and I could not wait to improvise the jig for measuring IOP.

DSC01578.jpg

 

 

 

Sorry for the late nudge on this one. NGY, can you remember the part number/style of this 6P plug for the IOP measurement jig? The SM does not identify the manufacturer/series number. It may well be a JST part as is common with Japanese kit - certainly my Tascam MDs seem to use JST PCB connectors, but a tiny variety!

Also the PCB inside the MD shell - is that one you designed/etched yourself? It's very neat!

Thanks, Kevin

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