Edit: Guess I had posted this in the wrong section by mistake and don't know how to fix it without just making a new post. I've gotten some information on reddit but am now here to look for more information about the fixyouraudio capacitor upgrade I recently did on my WM-DC2. I had replaced 2 220uF 4V caps with the provided 561uF 2.5V caps and would like to confirm this is an upgrade? The concern being going from 4V to 2.5V. And also that I did replace the correct ones? After finishing everything there is very low volume and I am looking for the cause of it.
Also, doesn't the DC2 have a more powerful headphone output than the others? I think it uses a DC-DC converter to increase the supply voltage to the headphone amplifier. If this is the case its possible the voltage of the output caps need to be rated higher too. I could be wrong, others on here might know.
mattb1970 not really, the DC2 has an output of 20mW per channel, D6C has 30mW per channel and the DD9 around 5mW per channel.
Here is the link of the kit I ordered. Says DC2. https://fixyouraudio.com/product/sony-wm-dc2-capacitor-upgrade-kit/
@Knife The kit is ok, as it is the voltage rating of the new capacitors. They operate at 1.35V, so the 2.5V rating offers more than enough headroom. You did change the right ones and the polarity is correct. How is the line out, does it work correctly ? How about the volume pot, does it produce any change in the output volume or not ? As for the upgrade itself, what it's meant to do is improve the bass response with low impedance headphones. For refrence, yes the DC2 does use a step-up converter, but what it powers is the following: the head preamp, line amplifier, muting circuit, PLL circuit for the servo. The rest (meaning servo itself, Dolby ICs and headphone amp) is powered with 3V battery voltage. But given these are coupling capacitors, they don't operate at the full supply voltage (which is 3V in this case), but at about half of that. So for this purpose, even 2V rated capacitors will work just fine.
Hello Knife, Nice job and hope you really enjoy the upgrade and that one the reasons I love a good pair of headphones because they can produce a good range . Sincerely Richard
Unfortunately did not test the line out but I will put it back together and test it. When changing volume it seems the same all the way around until the lowest point it goes lower. So from probably 2-10 its the same volume? This is my first time working on something like this so bare with me and thank you very much for more information!
I have put it all back together and the volume is slightly higher but the volume does not change between 0-10 at all? The volume is also louder through the line jack? Seems like maybe the volume pot is the issue?
So the volume went slightly higher just by putting it back together ? And before the volume would do something between 0-2 and not the rest and now (when assembled) it's doing nothing at all ? The fact that line out works means everything before the potentiometer is working just fine. If you put a lot of pressure on the volume pot while taking the case apart it may have been damaged, but I do not know if this is the case or not. Unfortunately without seeing the unit myself to find where the signal gets attenuated with the oscilloscope, it's hard to draw any conclusion. So I think it's better to double check those 2 output caps are soldered properly and eventually put the original ones back just to completely eliminate them as a potential issue. Cause it's strange that problem appeared immediately after replacing those caps. So there are 2 possibilities: either the caps themselves are bad or incorrectly installed or you did something else at the same time without realising. It is of course possible that this fault is completely unrelated to what you did, but that seems unlikely.
I should of mentioned the walkman wouldn't work at all until I did the recap. And all my solder points look solid. Should I remove the volume pot to inspect it?
Ok, first of all you don't need to quote the previous post since it's just before your own. It only adds redundant information and makes the thread harder to read by an outsider looking for information on a certain topic. You can edit and delete the quotes for better clarity. Second, the fact that it did not work at all before is an important piece of information. So you replaced all capacitors, not just the 2 output ones. The other ones are not in the audio path, so even if they were bad (open circuit), they won't cause the unit to not work at all (no sound). For the time being, check the potentiometer with a multimeter: measure the resistance between the wiper (center pin) and one of the other 2. See if that resistance changes with rotation of the wheel or not. Also check the voltage on pin 5 of the headphone amplifier IC: it should be 0V during operation. Anything higher than 1V will mute the amplifier.
Removed previous quotes. To catch up on the story of this thing: When I bought the walkman it wouldn't turn on at all. No light, movement, or sound. After some research it seemed like I needed to open it up. While I'm in there I replaced main gear, reel gear, belt, full recap w/ upgrade (There was 2 leaked caps). Put it all back together and now everything works except volume. I will get it checked with multimeter and respond here with what I find. Thank you very much for taking your time to help me.
Isn't it possible to bridge the volume pot on the solderside and hear if the signal gets through directly?
It was in fact the volume pot. The 2 metal piece on the inside were loose from the plastic knob and I had to use string and epoxy to repair as I found on another thread. I now have adjustable and loud volume, but only on the right side? Any suggestions? Headset isn't the issue.
Given what you have discovered with the potentiometer, I would make sure that both channels of the pot are actually working before going anywhere else. The most likely scenario at this point is you need to do a little more work on that pot. Given one channel is working, the headphone amplifier is clearly not muted (as there is only one muting signal). And then what do we have more in the signal path ? A bad TA7688F is pretty unlikely unless unit has been powered with reversed polarity but that would also fry the CX20084 which is clearly not the case here. And then there's not much else: broken traces, cold solder joints on the headphone jack (but both are pretty unlikely).
A bad TA7688F is definitely possible. The one in my DC2 failed completely on one channel for no reason whatsoever. Check for something more simple first like a bad joint on one of the legs, given that you have done work in that area of the board, albeit on the other side.
@Knife On this topic: @Valentin replaced the capacitors of my DC2, with no noticeable change in the end. I just wanted to have it done - the old ones were not leaking. Some stated in the past that it improved sound quality of the DC2, but not for mine.
It is to be noted I used normal capacitors (polymer), not audio grade ones as those cannot be found in Europe in these small packages. Have used such audio grade caps in other audio equipment in the past and to my ears the results are debatable, hence why I do not want to argue about that. My measurements do indicate that the old Nippon Chemicon ones are usually still within spec. Capacitance spec (on any electrolytic) is +/-20%, so a 220μF capacitor measuring 176μF is within spec. It is also to be noted that even a new 220μF capacitor will not measure exactly 220μF, but less (and I am reffering to the good quality ones). Of course, if one wants to improve the bass response for low impedance headphones, then using a 330μF, 470μF or even 560μF is the way to go. ESR is also lower on the higher capacitance ones, however given the DC2 has a 3.9Ω series resistor on the output the ESR of the coupling capacitors will not matter as it's 1-2 orders of magnitude smaller. It is to be noted it's not recommended to bypass this resistor, as it's used as a phase compensation circuit along with C7. It will also limit the current if a short circuit happens on the output. This 3.9Ω along with the TA7688F output impedance (which is 1-2Ω as well) will mean the output impedance of the headphone output is quite high, hence the reason why the unit will sound better with an external headphone amplifier, at least with low impedance headphones. With high impedance ones (like 80-300Ω) it won't matter. So probably the best improvement is to use an external headphone amp, especially because this unit does have a line out, so you can bypass the TA7688F entirely resulting in a lower noise floor and better driving capability.
