Sony DHC-MD313 CD Player - Component Identification / Repair

[aod_]

Hi All,

I’m very much a newbie to electronics, but have had an interest for most of my life. I’ve been doing a lot of reading  / research into basic electronics, theory, tools, and watching repair videos and tutorials etc. This was to try and get a BBC Micro computer working for a friend.

Having recently repaired the PSU of the BBC Micro (just replacing some Caps and learning Soldering skills), I’ve been tinkering with a few other things to try and repair them.

I bought this Sony DHC-MD313 in December for £5 as it didn’t power on and having been trying to get it working ever since.

(attachments don't seem to insert inline for me...   )


The power issue fixed itself after I took the cover off, removed the transformer, put it all back and it worked.

The issue I’ve been trying to solve though is with the CD Player, which wouldn’t read discs. I put a lens cleaner in and about 2-3 / 10 times it would read the CD and play the audio instructions, other times it just shows ‘no disc’

I’ve taken it apart and reassembled countless times to check out the CD Player module – just looking at it and checking the mechanisms.

It didn’t get any better, in fact worse, as the tray no longer ejects, or returns – so I thought I’d check out the motor on the CD Player.

With the CD Player module out of the case and disconnected etc, I found the spindle motor and tested it with a 9V battery on the + / - terminals – it span up fine. This might not be the right thing to do, but just wanted to narrow down things that might not be working.

Note, I don’t have a multimeter at the moment, or really have the skills to use one.

I then put it all back together to see if anything worked differently.

It powered on, but still the tray wouldn’t budge, and after a few seconds there seemed to be a sort of power surge and it powered off. I turned it back on – it did the same and powered off.

Then I had the smell of magic smoke (although no actual smoke).

I unplugged and left it for a few days, and have just ventured back inside to find the culprit.

There are tons of capacitors in this thing and they all looked fine, until I came across this odd looking thing I’ve not seen before.

I assume it’s a capacitor but it looks like it’s held it place with metal sprung contacts – perhaps a sort of battery? Anyway it looks like it’s blown, and wonder if someone can advise what it is, how to remove it, and replace it?





Also if you have any other ideas about what I should do next with trying to repair the CD Player, I’d be very appreciative.

[bob91343]

That could be a super capacitor but more likely it's a battery.  You need to get a meter so you can measure if it's got voltage on it.  Trying to repair something when you have no test equipment is like trying to read a book in the dark.

[Fraser]

PCB annotation next to the failed part says “C579” so it is a Supercapacitor. These sadly can leak onto the PCB and cause a lot of corrosion of the copper PCB tracks, component leads and can sometimes create a conductive path between component leads with odd effects resulting. When fitting a new Supercapacitor, the PCB needs a thorough inspection, repair and clean before considering the job completed. If the capacitor electrolyte has soaked into the PCB material, there can still be strange behaviour from the equipment through inter-component conduction.

The value and voltage of the Supercapacitor will be written on its casing.

Fraser

[Fraser]

Some reading on Supercapacitors and pictures of the case format used in your equipment ......

https://www.electroschematics.com/supercapacitors/

Fraser

[Fraser]

Regarding the CD player and “no disc” situation. In my experience this is most often caused by a failure of the laser diode. It’s laser emission power drops off and eventually the reflection from the disc is inadequate for good reading by the detector on the reading side of things. You will sometimes find that such a unit will read some discs but not others. This is due to variance in the reflective coatings used on the discs. Eventually the laser becomes so degraded that the detector cannot even see the disc and the auto focus tries to provide a focus but fails.

The solution to the failed laser is either to replace the whole laser deck assembly as they are surprisingly inexpensive, or to replace the laser assembly that contains all the laser, detector and optics of the laser reading section. Replacing just the laser assembly is more involved as it requires disassembly of the laser sled and careful re-assembly, followed by correct lubrication. It is often better to buy the whole deck that includes a new spindle motor, laser head and all the parts needed to make it work. It just needs a few ribbons and terminated cables to be connected. On older CD drives there were laser bias adjustments and ‘eye pattern’ tests to do using an oscilloscope but modern units are normally self setting and there us no need fir the adjustments in most cases.

The failure of the CD tray to open is often due to degradation in a rubber drive belt that links the tray motor to the CD tray mechanism. If it starts slipping, it needs to be replaced.

It is often more expensive to repair an old budget HiFi CD deck than it is truly worth. The replacement parts can often be found from 3rd party suppliers on eBay but do consider the total expenditure versus the value of the unit to you. I repair some old kit that is not truly economic to do so but that has sentimental value to me.

I attach examples of complete laser decks and just the laser head. These are NOT the parts you need for your unit, just examples. The laser head costs £8 and the complete deck is £15 in the UK. So you see why we replace the complete deck rather than mess with a laser and worn deck parts.

Fraser

[Fraser]

To find out what CD deck you would need, look for it’s ID printed on the metalwork, as in the attached picture.....

[Fraser]

Sadly the old MD313 is not really worth repairing unless you just want to learn from the experience or love the model. They sell cheaply on eBay......

https://www.ebay.co.uk/itm/Sony-DHC-MD313-CD-amp-MiniDisc-amp-Speakers-with-remote-control-/164733035476?mkevt=1&toolid=10044&var=0&customid=CjwKCAiA4rGCBhAQEiwAelVti5NNMSClWPpnAQB_QOacaiTgKrOnO5rEy6eDTqp1kQeFaEFvPlN2ABoCQMUQAvD_BwE&mkcid=1&campid=5338268676&mkrid=710-53481-19255-0&nma=true&si=%252BUbd4rK1QmP%252Bm8OCgnmmaTYmv%252BY%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

£30 makes them too cheap to be worth repairing in most cases. I hate saying that though as I tend to enjoy repairing kit, even if not exactly a sensible economic proposition ! I once spent a small fortune on an old Ferguson Videostar Stereo VHS VCR that had been lightning damaged, just prove to myself that it could be saved ! I bought a lot of replacement expensive IC’s fur that unit but got her running well again. She went to the dump many years ago as she was just not needed. I still have the Service manual in the loft !

Fraser

[aod_]

That could be a super capacitor but more likely it's a battery.  You need to get a meter so you can measure if it's got voltage on it.  Trying to repair something when you have no test equipment is like trying to read a book in the dark.

Thanks alot, I realise a multimeter is essential for troubleshooting, but for now hoping to get away without one until I feel ready. In this case I might be lucky and just be able to replace some parts.

[aod_]

Sadly the old MD313 is not really worth repairing unless you just want to learn from the experience or love the model. They sell cheaply on eBay......

https://www.ebay.co.uk/itm/Sony-DHC-MD313-CD-amp-MiniDisc-amp-Speakers-with-remote-control-/164733035476?mkevt=1&toolid=10044&var=0&customid=CjwKCAiA4rGCBhAQEiwAelVti5NNMSClWPpnAQB_QOacaiTgKrOnO5rEy6eDTqp1kQeFaEFvPlN2ABoCQMUQAvD_BwE&mkcid=1&campid=5338268676&mkrid=710-53481-19255-0&nma=true&si=%252BUbd4rK1QmP%252Bm8OCgnmmaTYmv%252BY%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

£30 makes them too cheap to be worth repairing in most cases. I hate saying that though as I tend to enjoy repairing kit, even if not exactly a sensible economic proposition ! I once spent a small fortune on an old Ferguson Videostar Stereo VHS VCR that had been lightning damaged, just prove to myself that it could be saved ! I bought a lot of replacement expensive IC’s fur that unit but got her running well again. She went to the dump many years ago as she was just not needed. I still have the Service manual in the loft !

Fraser

Firstly thank you so much for taking the time to reply and all the fantastic information in your posts.

Regarding the supercapacitor thanks for the info, does it look like it's just held in by sprung contacts? Can I just pull it out and then push in a new one?

I will see if it's leaked but having checked yesterday it looks clean around the area and below. Maybe I've been lucky.

Thanks for the awesome advice on the CD Player and laser diode.

Reading your comments I think I will look into a replacement CD deck for this unit if it's cheap and see how that goes. I don't really want to spent much more time and money on it, but I would like to use it if I can get it working, as it's a lovely neat little system.

There's also a tape desk which I have for it and that works so would love to have it all working. 

Most of the MD313s I've found are about £60-£100, and I nearly paid £50 for mine, but then as the seller discovered it didn't power on, he sold it to me for £5. So I can afford to spend £20-£30 on it, if it sorts it out.

As the power isn't an issue anymore, fixing the CD player and replacing the supercapacitor should hopefully do the job!

I can relate to the story about the old video player!

The BBC Micro computer I mentioned, was supposed to just be 'turn it on', check boxes of games work and sell them (for a friend).

6+ months later I've invested in an array of soldering tools, learnt soldering and electronics basics, and turned my living room into an amateur electronics lab!

I've fixed up the BBC and think I can finally start the job I meant to last summer!

[tooki]

First of all, I of course think it’s good that you wanna fix it up!

With that said, I suggest you abandon the “throw stuff at the wall and see what sticks” approach to the repair (which can result in damage) and instead take a step back and do a bit more prep. For starters, you can easily find the service manual for it: https://elektrotanya.com/sony_hcd-md313_sm_2.pdf/download.html

Note that DHC-MD313 is the model number for the whole system, but you need to search for the model number of the individual component, here HCD-MD313. (This is presumably printed on the back panel, as on most Sony gear.)

The service manual has comprehensive adjustment procedures, waveforms, and schematics. But you absolutely must have (and know how to use) an oscilloscope to perform laser power adjustments. If you start fiddling with the laser power potentiometer without the scope, you risk turning it up too high and burning out the laser diode. (This model is not self-adjusting.)

The super cap is not in spring contacts. Those are welded-on legs. Service manual says it’s 1F, 5.5V.

Test gear is not optional in electronics. The absolute rock bottom bare minimum IMHO are a bench power supply, a multimeter, and an oscilloscope. Without these, you are, as someone already said, just stumbling around in the dark.

[aod_]

First of all, I of course think it’s good that you wanna fix it up!

With that said, I suggest you abandon the “throw stuff at the wall and see what sticks” approach to the repair (which can result in damage) and instead take a step back and do a bit more prep. For starters, you can easily find the service manual for it: https://elektrotanya.com/sony_hcd-md313_sm_2.pdf/download.html

Note that DHC-MD313 is the model number for the whole system, but you need to search for the model number of the individual component, here HCD-MD313. (This is presumably printed on the back panel, as on most Sony gear.)

The service manual has comprehensive adjustment procedures, waveforms, and schematics. But you absolutely must have (and know how to use) an oscilloscope to perform laser power adjustments. If you start fiddling with the laser power potentiometer without the scope, you risk turning it up too high and burning out the laser diode. (This model is not self-adjusting.)

The super cap is not in spring contacts. Those are welded-on legs. Service manual says it’s 1F, 5.5V.

Test gear is not optional in electronics. The absolute rock bottom bare minimum IMHO are a bench power supply, a multimeter, and an oscilloscope. Without these, you are, as someone already said, just stumbling around in the dark.

Thanks a lot tooki - I absolutely appreciate the need for more gear to properly diagnose and fix this sort of thing! At the moment I'm perhaps just below the stage becoming a hobbyist, but right now I don't plan on taking it a whole lot further by investing in scopes and power supplies etc - yet.

For the potential cost of around £20-£30, I'm hoping to be able to get all the parts I need (replacement CD deck and super cap), and with a bit of luck, fit them in and it might all work. If it doesn't I'll probably sell it for parts and get a working one.

That is assuming, the replacement CD deck doesn't require any fine tuning to work. I know you said there are procedures and adjustments that can be made in the service manual - and if you think it's going to be essential to carry this out regardless, then I'll admit defeat here, as I'm not in position at the moment to invest the time and money (in more equipment) just to get this CD Player working!

Perhaps later in the year or next year I might decide that I want to delve further into electronics, and get a few more things like you suggest.

I'll have a look in the service manual to see if I can find the part numbers I need, as I'm struggling to find one for the CD Deck as suggested by Fraser above.

I've posted pics of the Laser unit and the CD tray assembly. Not sure if the part numbers are on them, but can't find anything ref the green printed text on the metal part of the laser assembly.

I'm also considering replacing the ribbon cable as one end looks a bit roughed up and it might not be connecting properly back to the PCB

[helius]

The green stamp looks like a factory approval mark, with Japanese Imperial date code.

Flat flex cable (FFC) can take a fair amount of abuse, but be sure not to twist or yank it more than necessary. If it is just a bit corroded on the contact area, that can often be cleaned with alcohol, and sometimes abrasive such as a fiberglass brush or pink eraser.

[tooki]

Thanks a lot tooki - I absolutely appreciate the need for more gear to properly diagnose and fix this sort of thing! At the moment I'm perhaps just below the stage becoming a hobbyist, but right now I don't plan on taking it a whole lot further by investing in scopes and power supplies etc - yet.

For the potential cost of around £20-£30, I'm hoping to be able to get all the parts I need (replacement CD deck and super cap), and with a bit of luck, fit them in and it might all work. If it doesn't I'll probably sell it for parts and get a working one.

That is assuming, the replacement CD deck doesn't require any fine tuning to work. I know you said there are procedures and adjustments that can be made in the service manual - and if you think it's going to be essential to carry this out regardless, then I'll admit defeat here, as I'm not in position at the moment to invest the time and money (in more equipment) just to get this CD Player working!

Perhaps later in the year or next year I might decide that I want to delve further into electronics, and get a few more things like you suggest.

I'll have a look in the service manual to see if I can find the part numbers I need, as I'm struggling to find one for the CD Deck as suggested by Fraser above.

I've posted pics of the Laser unit and the CD tray assembly. Not sure if the part numbers are on them, but can't find anything ref the green printed text on the metal part of the laser assembly.

I'm also considering replacing the ribbon cable as one end looks a bit roughed up and it might not be connecting properly back to the PCB

The part numbers for both a whole CD mechanism or just the laser pickup are right on the cover page of the service manual. (Sony is really good about that!) I actually don't know whether replacement CD mechanisms come preadjusted or not, and whether that adjustment holds over time (since those mechanisms will have been sitting on a shelf for quite some time by now). Maybe Fraser knows?

Perhaps you can find a makerspace or similar where you can use some test gear before deciding whether or not to take the plunge and invest in it yourself, since the cost does add up!

[Fraser]

Laser current comes pre-set on all of the SONY laser assemblies I have used. The laser current trim pot on the laser head is usually locked in place with a paint seal. No adjustments have been necessary in the CD unit. I have not worked on the MD313 though and much depends upon the specific design age as more recent designs are far more tolerant of a new deck assembly.

With regard to damage to the tip of the ribbon cable.... if the damage is minor, the end may be trimmed back a mm or two with a sharp scalpel and ruler. Cutting with scissors can be challenging due to the reinforced tear to the contact area. Replacement ribbons are cheap if a new one is needed.

Fraser

[aod_]

Thanks again for everyone's input.

I’ve found all the part numbers I need, but struggling to find anything available.

CD Unit: CDM13C-5BD19

I’m not too surprised about not finding the CD Deck Mechanism as it’s probably quite old now I’d imagine not manufactured. The closest thing I could find was this, but it’s for a slightly different model, doesn’t come with the Laser Head and is out of stock!

http://www.i-service-solutions.com/shopexd.asp?id=14163

For the Supercapacitor the P/N is: 1-110-489-11

If I google this, the following comes up, but it’s not available to export to the UK. Perhaps I could get a generic part for this, if they are available?

https://sony.encompass.com/item/1498401/Sony/1-110-489-11/

Failing that I’m probably ready to give this up as I’ve found myself quite deep into a rabbit hole now, and it seems with parts difficult to source and repairing possibly beyond my skills and knowledge, perhaps quit while I’m sort of ahead!

[helius]

Small supercapacitors are completely generic. Just search Panasonic, NEC-Tokin, and Eaton for "EDLC": Electric Double Layer Capacitor and the value (1 farad) and voltage tolerance (generally they are all 5.5 VDC). That case style is called "VH" or vertical thru-hole mount.
https://octopart.com/search?category_id=4166&capacitance=%281+F__1+F%29&voltagerating_dc_=5.5&orientation=Vertical
RS has the Panasonic parts in stock; ensure that the part has a "V" in the name.