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Old 29th Apr 2020, 9:53 pm   #1
saxmaniac
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Default Sony WM-D6C dc converter

Hi folks
I need to replace the 6v to 12v converter. I've looked through Farnell, Cricklewood etc and it's hard to find the right thing. It needs a regulated output supposedly 11.6 volts I think but anything from 9 volts will work. I know I'll never get the original type but any ideas what to search for and where from? I know ive got to do a bit of construction to make it fit!
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Old 29th Apr 2020, 10:06 pm   #2
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Default Re: Sony WM-D6C dc converter

You may not need to replace it. They're eminently repairable if you're comfortable working with smallish parts. There's even a circuit diagram in the service manual, though it's shown back to front (input versus output) to try and confuse those who would repair it.

On mine, one of the tantalum capacitors had gone short circuit (surprise) which had burnt out one of the filter inductors. New inductor, new capacitor, both from the bits box, and it's back in action.

A replacement generic boost converter won't have the filtering that the Sony part has, which could lead to nasty noise problems, especially if its switching frequency beats with the bias oscillator.

Chris
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Old 30th Apr 2020, 7:47 am   #3
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Default Re: Sony WM-D6C dc converter

Ah thanks I'll have a look at that. This was a project that had a sat half done for a few years, only just got time to resume.
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Old 30th Apr 2020, 9:19 am   #4
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Default Re: Sony WM-D6C dc converter

Out of interest looking at the schematic for the WM-D6C I can see the circuit of the DC to DC converter (designated CP 304) but I cannot easily see its components listed as to their type/values, are these components listed in the manual ?
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Old 30th Apr 2020, 12:24 pm   #5
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Default Re: Sony WM-D6C dc converter

Just had a look but there's no markings to identify them on the circuit, it's the first time ive actually looked at the Dc _Dc board, it looks like discrete components inside the module, I had assumed it was an ic. I'm going to open this one up later so I'll see if it's possible to make out any values
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Old 30th Apr 2020, 1:18 pm   #6
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Default Re: Sony WM-D6C dc converter

Have you seen the good write up on it in the link above that Chris provided at Post # 2.
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Old 30th Apr 2020, 2:58 pm   #7
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Default Re: Sony WM-D6C dc converter

i.e. here: https://martin-jones.com/2019/01/01/...verter-repair/
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Old 30th Apr 2020, 3:08 pm   #8
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Default Re: Sony WM-D6C dc converter

The component values aren't listed in the manual, but they're readable from the components themselves once you've scraped the blobs of grey potting compound off. There's nothing unusual in there, just straightforward discrete components and a little transformer which is very unlikely to be faulty.

The module is also easy to test on the bench. Given a 6V power input it should produce about 10.8V at the output.

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Old 30th Apr 2020, 5:21 pm   #9
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Default Re: Sony WM-D6C dc converter

Thanks for the replies, I hadn't realised that was a relevant link above. Good tip about the input and output being reversed in the manual! An initial glance tells me that I've got a burnt choke, probably due to tantalum caps, but two semiconductors burnt to a crisp. I'm not sure at this stage whether they're diodes or transistors as they're packaged the same, but I'll have to map out the layout to identify what's what
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Old 2nd May 2020, 9:52 pm   #10
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Default Re: Sony WM-D6C dc converter

Just an update, drew out layout with component values when I could identify them, which I'll try to post here in case they're of use to anyone else.
Replaced temporarily the blown transistor t1with general purpose npn, tantalums read ok, input inductor had been roasted but not open circuit so good result but intend to replace inductor and tantalums as precaution
Attached Files
File Type: pdf wm-6c DC-DC converter print side .pdf (1.29 MB, 804 views)
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Old 8th Jun 2020, 3:48 pm   #11
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Default Re: Sony WM-D6C dc converter

Hi all,
I think that I have the same issue with a faulty D6C that I have, the motor turns etc etc but there is no sound from either headphone socket or the line out. Not sure which model of the supposed four iterations I have but is either gen II or gen III as does not have the birdsnest wiring but has an amorphous head. Thing is that all sites I have found talk about testing the DC-DC converter to see whether output is near 11V but there are no diagrams on a photo of circuit to say where to test - grd easy but where to put positive probe? Also does the unit need to be in "play" or is the rail on 11v till the micro switch? Also again no photo of the actual points to unsolder to get the offending article off. one web site just says "you will know what to do" and the site above is great but again assumes you are familiar with the unit I believe?
Sorry if the above appears a "duh" moment but I am totally new to this walkman, I can read circuits etc but the service manual I have found is no real help and does not appear to be for my specific gen unit ie I cannot locate the DC-DC unit on the layout plan as it shows IC601 in the DC-Dc position?

Thanks in advance if anyone can shed any light/help?
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Old 9th Jun 2020, 8:13 am   #12
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Default Re: Sony WM-D6C dc converter

The main difference between models is that the very late ones had glassfibre board and surface mount components. I'm not familiar with these but the majority are the earlier type. The 11v converter is on a separate board under the main one, if battery compartment is on the right, it's in the bottom right hand corner looking at the main pcb. There's 3 wires connecting to the main board, 0v black, 6v in red, 11v out, orange (from memory!) So very simple to test, just need the machine in play to power it up. It's repairable but very small and fiddly. Inside the can is a small pcb with a few discrete smds, I had the regulator transistor blown to smithereens. It's not too critical as to the replacement and the unit is best repaired off the machine with a separate 6v source
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Old 9th Jun 2020, 8:22 am   #13
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Default Re: Sony WM-D6C dc converter

The link in Post 7 will also help.

Last edited by DMcMahon; 9th Jun 2020 at 8:31 am.
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Old 9th Jun 2020, 8:27 am   #14
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Default Re: Sony WM-D6C dc converter

Thanks for reply

the DC-DC converter in my D6C is on the main board but on the reverse. I have now tested the converter and it is pumping out 10.88v so I believe it is all good.

Now the issue is that the motor has stopped working and still no output from the sockets etc.

I think the motor stop is something to do with the autostop and will google for any answers unless anyone has a fix here.

Still no output though so I assume I move on to testing/replacing caps, but am unsure which path to take ie which ones do I check first and should I be checking ICs as well?

By the way I have found a service manual addendum with my type board layout on a Hungarian web site, however unlike earlier service manuals the pin voltages are not shown but I asssume they remain as on older versions?
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Old 9th Jun 2020, 12:41 pm   #15
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Default Re: Sony WM-D6C dc converter

Don't just jump into replacing caps unless there's a reason, you'll do more harm than good. You must have one of the later fibreglass versions so I'm not familiar, don't know if it's electrically the same. First thing is to check none of the small wires have dropped off the board. It's an idea to take close up photos before doing any work so you can identify where wires go. Then dc voltage checks, if the motor has suddenly stopped working it's more likely that you've disturbed something than a fresh fault
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Old 9th Jun 2020, 12:45 pm   #16
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Default Re: Sony WM-D6C dc converter

The autostop on playback is mechanical by the way. The stop mechanism for fast wind depends on a photo led reading a serrated disc connected to the feed spool and cuts current to the motor. This is all mounted on a sub board if it's the same as earlier type
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Old 10th Jun 2020, 11:16 pm   #17
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Default Re: Sony WM-D6C dc converter

An update and grateful for the help to date

I cleaned out the mechanics and regreased as there were some stiff gears - probably age and lack of use. I also replaced the drive belt and capstan rubber whilst I was there. So mechanically the unit is now in good order.

Whilst trying to sort out the motor fault I unscrewed the separate board above the photostop wheel and found the leaf spring muting whilst record button pressed was stuck closed, fixed that and with all boards back in place I have volume and I have an active playback head - hopefully one issue resolved!

As an aside the manual says there are 3 leaf springs but I can only see/find 2 the power by the motor and the mute on record under the board - where is the third one?

However, the motor still will not move, I know it works as I have connected the motor directly and I have 10.98v now at the DC DC convertor. What I failed to mention before is that the motor died gradually that is it worked for a while then stopped, I hit the stop button and pressed play and it worked again for a short while then stopped again. This happened about a dozen times till it has now stopped altogether.

I have checked all the connections and wires and I can see no issues there - any ideas where to start?
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Old 11th Jun 2020, 7:41 am   #18
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Default Re: Sony WM-D6C dc converter

If it runs for a few seconds then stops, just give the supply spool a spin by hand, does the motor again run then stop? If so it's something to do with the auto stop on fast wind. There's another leaf switch that's activated by the ff or rw buttons to bypass this for playback. Could be a wire off or switch dirty or not working. That's the area to look anyway
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Old 11th Jun 2020, 4:49 pm   #19
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Default Re: Sony WM-D6C dc converter

Really appreciate the reply and an update,

- before I remove the motor and test it some readings etc and unfortunately the motor does not run if manually spun. I have now cleaned all leaf switches and all OK there.

As an aside the SN is 273312 if that helps?

At pins 5 and 8 of IC601, I have on "play" 0.8v and 6.17v respectively and just checking the other pins going from pin 1 to 16 - 0.16v,0.23v.1.3v,0v,0.8v,0.8v,1.6v,6.17v,1,58v,0.4 2v,0.25v.0.1v,0v,0v,0v,0v. I have also checked Q601 and read 6v at the base only, emitter etc 0v.

The current draw on play. rewind etc is between 120mA and 125mA.

Does any of the above help the diagnosis of the problem?
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Old 11th Jun 2020, 8:49 pm   #20
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Default Re: Sony WM-D6C dc converter

The emitter of q601 should have 6v on it ?
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