TPS-L2 Walkman Loud Distortion at near/full volume.

[jercool]

Hi, I am writing this thread to bring up an issue I am having with a TPS-L2 that I have that seems to be having a problem. I have the later model TPS-L2, the one where it says walkman at the bottom of it. The walkman is in excellent physical condition. There was only some corrosion in the battery compartment. I replaced the belts inside of the unit. Anyway, I am having a problem with the audio when I put it near full volume or even near full. The sound tends to get a very loud low frequency distortion noise behind the sound. I thought this might be some sort of design fluke of every late TPS-L2 but then I went to youtube to listen to TPS-L2 playbacks. They didn't seem to have nearly the level of distortion that I am experiencing. Now what I have realized is that when I press on the HOTLINE button the distortion doesn't go away, I can still hear the distortion. Im pretty good at soldering and looking at repair manuals, however I am not the best at understanding circuit design and pinpointing/understanding exactly where a problem may be. I am getting a hint that maybe it is a bad capacitor. One thing that I did notice about my unit is it has Light Blue Sanyo Aluminum Capacitors inside of it. I read on one forum thread that these lower voltage capacitors have been known to go bad and should be replaced. This thread was talking specifically about a Pioneer unit of some sort so i don't really know if the info would help. I don't really want to go willy nilly replacing capacitors right away before I know that they are the cause of the problem. One thing that I did notice is that as the batteries begin to be used and lose power, the distortion does go away significantly. But by that point the batteries are half used. I have included pictures of the PCB with the blue capacitors visible. I have also included a link to a google drive folder that has recordings of different tapes that I recorded using a good usb capture device. In those recordings I press on the HOTLINE Button occasionally to show that the distortion is even present when it is pressed. I have searched all over the place for people who may have the same problem as me with no avail. I might be crazy and this is just something that the TPS-L2 has always been known to do or there is actually something wrong with it. I think that there is something slightly wrong with it
If anyone knows what might be the problem with the unit please respond to this thread. It could maybe even help others with this problem.
Thanks!

Here is the link to the google drive folder containing the recordings:
https://drive.google.com/open?id=1RoxnyC_lXnovooIsJPqxakCZ_tNpfQNQ
*Note I converted them to MP3 for those who don't want to download the files so they could just be played in browser via google drive. There are also the original M4A files for those who want them.

 

[stragulus]

I am not qualified to comment on the distortion. It may very well be a component out of spec. Mine does not have any of this distortion at all.

I do hear that the mechanism runs very rough. I restored a TPS-L2 myself and it is very difficult to get to run without too much W/F. I replaced all the rubber parts including idler tires, but most importantly the capstan against which the pinch roller presses was too polished from wear, offering no grip for the pinch roller. The solution is to dunk the top part for 5 seconds in a Ferro Chloride (FeCL3). This roughens the surface enough to get more grip and thus more constant playback speed.

 

[jercool]

Yes stragulus, when I first serviced the unit, the motor wouldn’t even start up. After searching up a fix for it I found out that a good fix for this soaking the motor in some 91-99% percent isopropyl alcohol and then using gun oil to lubricate the motor shaft. I use Hoppes gun oil. You can get it on amazon it’s great. Anyway after I did that I had to replace the belts. Then problem 2 came. The mechanism wasn’t moving properly. The little arm thing that goes back and forth kept missing it and wouldn’t be caught. That is part of the Auto-Stop function as I discovered in the service manual. After that I look up the problem. It took about 1 week until I finally found out that I had put the belts backward. Lol. So I fixed that and all seemed fine. Then I noticed this bad W + F. I realized that the pinch roller had an indentation on it maybe the play button was pressed in for many years idk but that would be why it had a mark in it. So everytime It would roll, it would make a audible “jump” if I had to describe it. I found some guy on eBay who was selling the very origional spare part that was made by Sony so it’s an official Sony service part. All seemed fine after that issue. But then I changed the batteries to fresh new ones. That’s when I heard the terrible distortion. And after I used the batteries for a while the distortion went away but by the time that it went away, the batteries were half full. This may be an indication that the higher voltage of fresh batteries could be tripping it up so that may eliminate some possibilities of things causing the problem. But I still don’t know because no one else has this problem with their TPS-L2. I feel like my case is a very rare one because I have googled to see if any others have brought up this problem with their unit to no avail, but that’s why I’m reaching out to all of you guys. Someone on this forum is probably more knowledgeable on the circuits in this thing and can respond.

 

[jercool]

My biggest fear is that the IC in the unit could be bad. This would be the most problematic as they are the hardest to replace as they no longer make them and I would have to hunt down some other product that Sony released unsung this IC as a donor. And that wouldn’t be a pleasant task. Either way I don’t believe that that is the problem because it appears to amplify the audio. The blame would most likely be on a capacitor I believe because they would probably be responsible for filtering out undesirable distortion from an audio signal.

 

[stragulus]

I did the very same thing to my motor, it was also stuck. I think I would trace the audio signal in your case and see at which point the distortion is introduced. An audio tracer is something you can very easily build yourself. Essentially really just connect a wire to ground, and another wire you manually touch to contact points in the circuitry that carry an audio signal. The other ends of the wire go to an amp. The only thing you'll want to do is put a small capacitor in between the positive wire and the amp to protect the amp. That's how I found most audio issues on boomboxes.