Hello all, I recently serviced a DD-11 walkman, full recap and new belt, thing even before the recap sounded amazing just very quiet. I got it amazingly working from the original owner in Germany. Now that it has some real volume I can hear the tiniest distortion, it's only noticeable when music really picks up and it very rarely is at all even detectable. I believe it's the pinch roller as that was the only thing not replaced, and the sound immediately got as small as it is after the belt change. To get to the point, would anyone agree that it is likely the roller? As I tested the caps and they seem to have perfect contact, while the roller was just cleaned with roller rejuvenator.
I think by distorsion you mean wow&flutter (like the music sound a little wobbly). If that is the case, yes the pinch roller can certainly cause that, especially if it has an idnentation mark from leaving the unit in play with no batteries. I can only confirm that if you put pictures with the roller itself in different positions, to see if it has an indentantion mark or not, otherwise the picture of the unit itself isn't of any help. I also recommend lubricating the capstan bearing (use oil, not grease) if you didn't do so already. The harmonic distorsion caused by the electronics or the tape is a different thing, but I'm pretty convinced that is not what your problem is. I suppose you did not touch the Dolby level adjustements.
I'll take some pictures later to see if so. It's akin to a slight wobble yes, more of a slight drop in sharpness if I could describe it like a picture. Though from what I see right now there is a clearly discoloration in the shape of the tape in a cassette. That is one thing I've been wondering about, exactly how do you do that? I didn't see it in the service manual. Certainly didn't, didn't even know that was a thing till now haha.
The discoloration is oxide left from the tape. Put the unit in play and clean the pinch roller with a cotton swab immersed in alcohol until that discoloration disappears. Only then you can draw conclusions about the condition of the roller. I'll explain later about lubricating the capstan bearing. I don't think that procedure is shown in any service manual, so I might do a separate thread covering how to do that in general, on any walkman.
Oh cool I'll try that now, does it matter if it's 91% or 70%? Haven't been able to get a clear answer on that, but I have both handy. Hm I see, guess they never expected most of these electronics to last long enough for such a need. Great thanks for the help, I'll be waiting on that advice.
Either one will work, but the 91% will evaporate much faster, due to the much lower water content. I personally prefer IPA (99.9%) as it dries extremely quick, but not all people have IPA. I will make a separte thread in the coming days regarding the capstan bearing lubrication, as I must first take some pictures or find some suitable that I already have in order to explain everything.
I'm out of IPA but in that case I'll give the 91% a try, alright great sounds like that's gonna be an interesting post.
Alright gang, I've been doing some test, and I know exactly what the distortion is. I listen through a blank cassette with headphones in the car and it's the unmistakable sound of interference. Sounds the exact same as the noise I hear with my phone next to an older radio.
This one I believe however is coming from the car's computery screen thing they put in the new ones, as when I turn the car off it goes away.
Wow seems I'm a bit late to the party, this fellow here discovered this issue way before me. However it explains why when I plugged it into a speaker and listened through that it sounded perfect, as my aux cord is highly insulated.
You can bet it's coming from the car's computer system. You did not mention it only happens inside your car, that would have been an important hint that clearly points to something external. Given how old the unit is, it's likely that the EMC regulations at the date of manufacturing were not that strict, so it's not immune to interference. With today's standards, it should be impossible (if both the car and the player are indeed EMC complaint) to get such an interference. What is curious is the car's infotainment system has very high RF emissions. Probably it was only tested outside and the screen does not have good shielding (high speed digital signals create a lot of broadband emissions). I suggest changing the title of the topic to something like "EMI problem" or "RF interference", instead of "distorsion", because it's clearly not distorsion nor wow&flutter.
Well to be honest I still wasn't entirely sure if it existed, just the car under the radio is where it was most noticeable. I haven't actually used it in many places yet as I still have the skittishness from the EX line. Whenever they're "fixed" something else breaks, also it's rather fatter than the ones I'm used to especially with the case, so I haven't quite found a way to carry it in my pocket haha. Though the small bit of distortion I only noticed besides in the car is in the room I first played it, a room full of electronics like computers and large incandescent bulbs so that probably explains it, as the reddit ask did say it causes the headphones to antenna. Outside and in less crowded rooms it sounds perfectly normal, mainly the reason I wasn't sure it existed or was a roller issue. Since it's the model made for 1990s germany I can imagine the regulations of EMC were quite different than the modern USA. However likely it's the fm radio which could be the source as the storage area it sits in is directly underneath. Though the headphones I used are more of copper earbuds, so that think lanky cable likely makes it much easier. In that case I'll change it now.
I was engaged in a discussion in another thread regarding a DD11 that has a different unrealted problem and I remember something that might be useful. There are 3 small ceramic SMD capacitors near the headphone jack and judgind by their capacitance and how they're wired are clearly used for interference supression. I think it is worth checking those are properly soldered onto the PCB or if there are any broken traces in that area. Also check the chassis connection, as I see one marked on the schematic that is clearly different than the PCB GND.
They looked alright last time I opened things up, thankful to my past self I took a picture before starting work. Looks fine from what I can see, seems like it might just be the nature of the beast.
For EMC issues it's useful to identify whether the problem is conducted (through the 3.5mm audio cable) or radiated (though the air). If you hold your Walkman close to the screen, does the noise get worse? If yes then the problem is likely radiated emissions related and you need to either use a longer shielded 3.5mm cable and move the Walkman away from the source of the noise or improve the shielding inside the Walkman. If moving the Walkman close to the screen doesn't make the issue worse the noise is likely conducted through the audio cable and you could look for a poor PCB ground connection or damage to any noise filter components on the PCB next to the headphone jack as previously mentioned.
Alright lads, I've done a few more test. With what Matt I decided to fine headphones with a thicker wire, and found some rather nice over ears that have a fairly solid wire. Not even going to go into finding good non bluetooth headphones for a low price but these are fairly quality despite being 20$. From testing these pick up little to no interference when next to a source, to the point I have to touch the NFC point on my phone to them to get a bit of noise. I would say that's problem addressed, next order of business was replacing the pinch roller. Which if I must say what more troublesome than usual, I'm usually able to change them out with these two small pointy pins I use to push out the holding pins however this one wasn't having it. It came half way out but that's all, a "unique" feature of the DD 11 however allowed me to do a "controlled" demolition. As the pin doesn't actually go through the top hole with it being a square, I simply broke the top plastic. It's a clean break so it can be reglued if need be however seems fine with what was done. The service manual certainly didn't offer any assistance but I'd say this is a good fix.
