TDK Boombox 2-speaker volume pot

[zvat]

[SIZE=14.285714149475098px]hi all,[/SIZE]

[SIZE=14.285714149475098px]my beloved tdk 2-speaker boombox seems to breathe out life after a few years already. volume adjustment has become difficult lately and is now hardly possible anymore. that's really annoying but otherwise the boombox is perfectly alright. I was 99% sure that the potentiometer is worn out so I took the boombox apart and took out the circuit board with the pot on it, looked inside and yes, it's worn where the contacts move along. problem is, there is no possibility to obtain original spare parts from TDK, resp. Imitation.[/SIZE]

[SIZE=14.285714149475098px]has anyone had the same issue? or can anyone help with ideas how and where to find a suitable replacement pot (see pics)? I'm no technician, so I have no idea what to look for, specs-wise.[/SIZE]

[SIZE=14.285714149475098px]if there's no chance at all to get an alternative pot, which would be a real shame, I may consider removing the electronics altogether and putting in a simple amp with line-in.[/SIZE]

 

[blu_fuz]

You are screwed!!!!!


There is no replacement. If you can't fix the one you want your best bet is to find a beater TDK 2 speaker and pull the parts off you need.

If you are OK with non-original, you might have to modify the box and add a new power switch separate from a new potentiometer .


https://boomboxery.com/forum/index.php/topic/13196-how-to-get-inside-a-tdk-boombox/?hl=%2Btdk+%2Bpot


https://boomboxery.com/forum/index.php/topic/13064-what-the-heck-do-i-do-with-this-hunk-of-crap/?hl=%2Btdk+%2Bpot#entry165278

 

[zvat]

I'm affraid you nailed it with your first words...

thanks for the links. I actually used the first thread to get into the boombox. was very helpful, this guide with photos is fantastic! I'm not in a hurry so I'll keep watching for a used boombox or parts. Unfortunately, there's not a lot of those things around here (in Germany), it was already a rare find when I bought it almost new a few years back.

I don't care about original parts, as long as the thing works properly. A mod is ok too, if there is no other way. Perhaps I'll have it repaired by a skilled hobby tech, who likes a challenge and knows how to source a fitting pot. There must be someone in a city like Berlin.

Anyway, if there's any other idea on how to find a pot that fits or a working mod, let me know. Any hint is greatly appreciated.

 

[floyd]

can't you just buy a similar pot and replace the parts inside the pot you have .

http://www.ebay.com/itm/500K-Audio-Taper-Potentiometer-With-Solder-Lugs-Volume-Control-Pot-Alpha-/281446424279?hash=item4187839ed7:g:uEQAAOxyMZVTkMmB

 

[blu_fuz]

I see what you are saying Floyd, maybe you can transplant just the board with printed traces

Or if you were going to modify the box, you could use a "D" shaft audio pot, but it will not have the On/Off power clicks like the original TDK Pot is. That's why I mentioned you could probably use a standard volume pot but need to mod the radio to have a separate power switch located somewhere.


You should open the potentiometer, it might be an easy fix.

Good luck keep us updated.

 

[floyd]

joe i don't know much about the tdk , just figured he might be able to scrounge some of the tiny replaceable parts inside the new pot to fix the old pot. might not work or you just have to keep looking for a similar unit that's a closer match.

 

[blu_fuz]

For sure, I agree.

 

[floyd]

this part looks like it has more usable pieces.
http://www.ebay.com/itm/4x-Panel-Mount-PCB-6xStepx10k-D-Shaft-Rotary-Volume-Tone-Potentiometer-P-006-/390744586548?hash=item5afa313934:g:NrIAAOxyOlhS0QGM

 

[baddboybill]

First thing I would do is see if ohms are stamped on pot. There are plenty of pots with switches out there to try and match this one with.


Bad Boy Bill

 

[zvat]

I found a guy who seems to know a fair bit about audio pots. he's also a skilled tech and he's optimistic about finding a suitable pot. I'll meet him today and I think I'll have him repair the thing.

There's unfortunately nothing stamped on the pot but it's still soldered on the circuit board. I hope that once removed we will find the ohms on the back side of the pot. otherwise my tech will measure the resistance, that's no big deal he said. If the repair works out, I'll post here which pot exactly he used. I'll try to add photos too.

Floyd, the pot you posted looks similar on first sight but I'm not sure it's really possible to replace internals of a pot with those from another brand one. I love the idea but I'm affraid that there may be tiny differences in terms of build and function. When I looked into the TDK pot I found it has a non-removeable shaft, which makes replacing the print-on resistance unit impossible. Also, the shaft is coupled with the internal on/off switch mechanism, which seemed like rather special design to me. The TDK pot does also have two "feet" on it's back reaching through the circuit board, they have no function other than fixing the pot. All pots I found so far did not have these feet in this particular place. Nevertheless, I'm sure we'll come up with a workaround, in case there no exact match to be found.

I'll talk this repairing the pot idea over with my tech as well. And I'll post his answer, if it's worth mentioning.

I hope to be back with news soon

 

[zvat]

the TDK [SIZE=14.285714149475098px]is alive again![/SIZE]

We did some workarounds and some not so clean fiddling with the electronics, but the machine works again, that's the most important. As it turned out, my tech did not know much about pots at all, so he bought the wrong one... What you need, in order to get close to the original one is:

a pot with 50K Ohms, mono (not stereo!) and switch included (see pictures later).

My tech bought a stereo pot without switch, BUT at least with the right Ohms. We made it work anyhow, eventhough it's stereo. We simple did not connect the second stereo circuit to the circuit board. As there is no switch now, we had to bridge the two contacts on the circuit board with a tiny cable (see pictures). The TDK is now always on so I have to turn on / off by connecting / disconnecting the power cord. Not the cleanest solution but it works for now.

We did also have to use little cables to connect the pot to the circuit board, as the new pot did not have the long 90-degree feet of the original pot. That was not a big deal to get done (see pictures). The critical point is, how to properly anchor the pot to the circuit board, as it will be almost impossible to obtain a pot which comes those long "feet" on the back, as the orignal TDK pot has. You could use strong adhesive tape (removeable, like tesa power strips), or you can try to bend off some corners of the chassis and use them as "feet", which is what we did. However, these feet are tiny, so I doubt they will stay soldered in place forever.

 

[zvat]

this is the new "wrong" pot. 50K Ohms. As you can see, it's stereo (2 x 3 contacts). (A mono pot with switch should have only 2 contacts on the rear, where this one has 3 contacts)

 

[zvat]

Here you can see the new "wrong" pot already installed. You can also see the cables we had to add. And you can see that the shaft is grated down to proper length and to d-shape, in order to fit to the volume knob

 

[zvat]

Here you can s[SIZE=14.285714149475098px]ee how we bridged the on/off switch contacts (orange cable). The TDK Boombox is now always on. [/SIZE]

[SIZE=14.285714149475098px]However, I recommend to rather use a pot with switch included right away. I might change the new "wrong"pot some day when I find time for it. If I ever do it, I'll try to keep you informed[/SIZE]

[SIZE=14.285714149475098px]Thanks for all your ideas and assistance![/SIZE]

 

[blu_fuz]

That's way better than a busted blaster. Good job getting something to work for it.

 

[Billy Bill]

Thank you blu_fuz for the clean cut disassembling instructions ! You are amazing! I'd stress only one detail - pry the front plexiglas panel real slow, I mean SLOOOOOOW... Basically the point is to tire-out the glue by putting extra tension on it by prying. So do it gradually step by step and when you are at the end and almost done and speed-up a bit... boom and you broke it... no, that was me not you...

Thank you zvat too! Big help!

The same problem here, but 50k linear or logarithmic? Mine is the 3 speaker version but I'm assuming it's the same. Thanks again!

Cheers!

 

[blu_fuz]

Bummer to hear your plexi broke!!!!


Tip #12 was pretty clear LOL.

"12. work slow and carefull all the way around the boombox to pry the plexi away from the front case"