So I just replaced the belt which had melted away on my EX49, and the next issue raised it's ugly head - horrible motor / whine coming through the headset. Gears all seemed to be fine with no obvious cracks. I cleaned the head, rollers etc with propyl and also used demagnetizer with no improvement other than making the noise more consistent and less poppy. Reading up it sounds like the caps may need replacing, I found 15 of them, at least I think they are all caps - are the ones encased in little black boxes also caps? they are named Elect Chip in service manual. Just looking at the biggest one first (330MF) I noticed I could get a close match with a Polymer Electrolytic Panasonic - only diff is 2.5v instead of 2v on walkman. https://uk.farnell.com/panasonic/2r5svpe330my/cap-330-f-2-5v-20-radial/dp/2354778 Is it ok to used Polymer Electrolytic if the size matches, I read something about not using Polymer on the signal path, but this seems like a hybrid of some kind? If those little black boxes contain caps what do you replace those with - SMD caps just like the radial can one's? Are there any priority one's that are worth focusing on to resolve headset buzz, or is it worth going for all 15 of them at once? This will be my first attempt at proper soldering - so will be a challenge being so small, I'm getting some training SMD kits to practice on first. Oh - the service manual I'm referencing is for WM-2091, I assume that is close enough to EX-49? schematic layout appears to be the same. C104 22MF 4v (Elect chip) C114 4.7MF 16v (Elect chip) C204 22MF 6.3v (Elect) C214 4.7MF 35v (Elect) C301 47MF 4v (Elect) C303 3.3MF 25v (Elect chip) C307 47MF 4v (Elect) C308 47MF 4v (Elect) C311 22MF 6.3v (Elect) C314 330MF 2v (Elect) C315 47MF 4v (Elect) C321 22MF 4v (Elect chip) C602 2.2MF 50v (Elect) C603 2.2MF 50v (Elect) C605 2.2MF 50v (Elect) Thanks for any help.
no need to worry about C104 and such. What you hear is a 'grounding' issue and before going into "recap spree" check the continuity of the Ground (thick, Negative line on schematics) between the boards and parts. Usually when SMD electrolytics go bad (and for a few years in 1989-1990 there was a batch of a really bad ones!) you can see it. I do not see any evidently leaked caps on your photo, but when going for a recap start with decoupling/bypass capacitors: they are your prime suspects
Did you fully reassemble the Walkman before checking the audio? Sometimes the case screws or metal contacts are used as part of the grounding scheme. Check the ground (G) connection at the headphone jack socket and also the ground connection to the tape head. I normally use a multimeter set to continuity to do this.
Thanks Jorge and mattb1979 I have a good multimeter on hand, I wonder if you could be kind enough to steer me in the right direction as I'm trying to get my head around the tracers on the board. It was a good point you made re the case screws mattb1979 as I noticed that a key screw on the back of case goes right onto what looks like a grounding scheme (see image below) there is another to the right which simply holds a screw to secure down the motherboard which may also act as some kind of ground. I was testing with unit closed up and open, but I double checked after securing the 2 screws mentioned above and closing the back of the case up, but I still get the interference noise. It seemed to be predominantly on the right channel when music was playing if that helps to narrow it down? although when first pressing play interference is on both left and right, and oddly the music seems to come through approx 10-20 seconds after pressing play, gradually fading in and then becomes fairly clear, and speed seems good. although after pressing stop and then trying again after a minute or 2 the sound is gone again! I can see a ground point next to the battery section (top right) but which lines should I be checking continuity between?
+1 to @Silver965 !!! Also, from your follow-up note it seems that decoupling/bypass electrolytics is not the ((only)) glitch here. Before going for a recap make sure to clean the Volume and all the switches with DeoxIt: DeoxIT 5% Spray Contact Cleaner More than once I had this same problem because volume got dirty or damaged. Check and maybe re-flow solder joints for all the parts getting touched during normal use.
Thanks @Silver965 I've tried to identify the connection points - see image, but there are a few I can't find a hole in between the components you noted - does it matter if it's after an additional resistor? Also what kind of cable / connector do you use to link up to an amp from such tiny pin holes? The only one I have is an old Rotel 921, would that be suitable? This odd warm up behaviour where the music only starts coming through headset after 20 odd seconds of pressing play - would that not indicate a poorly preforming cap? There is a little bit of gunk around the 330mf cap, after swabbing around it with cue tip it's leaving orange stain on the cotton. But I definitely want to rule out continuity issues first. @Jorge I cleaned out volume and also the mega bass switch which seemed to affect the feedback when jiggled, I stuck the multimeter on the other switch connections and they seem to have continuity on all positions.
There is an electrolytic capacitor across the motor supply, I think it's C314 330uF in the bottom right hand corner of the schematic close to the DC IN socket. I would check or just replace this capacitor as it should suppress motor noise. The capacitor voltage rating should be 2V or more. If replacing C314 helps then of course it's possible that the other caps are also failing.
Hello... Mattb the capacitor in the lower right (red) and connected between positive and negative do not know if close to the engine .. but the same thing does the one on the left (Green).. would be to check both....Rossoe.. if the audio comes after a while you pressed play it may depend on the transistor highlighted in red but most likely from the capacitor in the blue circle ...(I can not read the values of the capacitors because when I enlarge the photo loses definition and I can not read ) as for the tests ... I use a small auto-built amp from about 1 watt to 3 1.5-volt batteries and use an incoming shielded wire with a 3.5 mono jack and on the tip of the jack I welded a piece of rigid wire as if it were a needle ... I connect the mass together with the circuit to try and with the tip of the touch jack on the points to be tested if there audio
Thanks @Silver965 I was checking this post - https://fixyouraudio.com/instructions/capacitors/ and noticed they mention tantalum caps, the equivalent for that 330uf would be - https://uk.farnell.com/panasonic/2tpf330m6/cap-330-f-2v-20-2917/dp/2354938 The one you highlighted blue is a 22uf 4v so I'm looking at this one as potential replacement: https://uk.farnell.com/vishay/t55a226m004c0200/cap-22-f-4v-20/dp/2455898 Do they look suitable? they are alot smaller but would hopefully fit being approx 3.5 - 5 mm in length Regarding grounding checks, in particular the headphone jack, should the below points show a continuity? as my multimeter shows nothing between those. joint looks solid to my eye, I don't have my soldering iron yet to reflow anything. Full manual is here: https://freeservicemanuals.info/en/servicemanuals/viewmanual/Sony/WM2091/WMF2095/None/SUPPONLY/
No come da schematico il jack per cuffie ha la massa collegata direttamente ai 30 piedi del cip 301 e non ha altre connessioni quindi ci deve essere continuato tra circuito negativo e jack ... verificare se le tre induttorie hanno continuato
Thanks @Silver965 I appreciate your help, I do indeed have continuity between the 3 inductors L101, L201 & L301. and the foot 30 from IC301 has continuity to Ground on headphone jack. I see now that leg 29 on IC301 heads to ground. The diagram is slowly starting to make sense. I'm going to order some Tantalum Polymer Capacitor's and see how I get on replacing 1 at a time starting with the biggest electrolytic 330uf 2v C314 (red) which I think is a decoupling/bypass cap like @Jorge mentioned. I'll try and test the other 2 you mentioned 22uf 4v C312 (blue) and 10uf 4v C405 (green) but they are tantalum and ceramic caps so I'm assuming they are less likely to fail?
@Silver965 I just read up on basics re testing transistors and did a few checks using multimeter on the on the Q302 you highlighted previously: The symbol shown above for this particular transistor does not look familiar to examples in my book - It appears they have built in resistors, so I may not have appropriate expectations for this test, however I assumed it looked like an n-p-n type transistor given direction of current, so I tested with positive on Base using 'diode mode' on multimeter and found no reading with negative on either Emitter or Collector, I then tested all other 5 permutations and the only combo that gave a reading was with positive on Emitter and negative on Collector! Is that expected? I also checked another Transistor Q301 (p-n-p) which had a more familiar symbol and the results were as expected:
Ok - that was fiddly and & tricky to keep her playing with the motherboard peeled up, so I checked against all the legs on that side of the IC with references, leg 27 seems to have the biggest deviation from Sony spec! I assume I should just have negative on ground and positive touching each leg? These figures were taken when it was playing. I could use the lower ground near the battery terminal, but top one titled 'BLACK' gave funny readings - not sure why.
Thank you for this post,it gives me hope to repair my wm-190. I looked at the 330µf and it has leaked,the other caps have no sign of leak, so i'll start from there.
Sad to see @Rossoe abandon his project. This thread is bringing new life to my WM-170. For the record; I believe that the "elect chip" were electrolytic capacitors; there does not seem to be any available replacement today. You can see as example C104 and C204 are pairs (left and right); the use of C104 as elect chip is purely to clear the cassette drive mechanism. I was able to replace C104 with a regular SMD electrolytic by removing the plastic base and mounting horizontally. I'll post a pic when I do final assembly. Only regret as I did a complete recap; I should have done one be one; following Silver965's start at the preamp and work outwards. replacing only what was necessary.
