Volume knob broken off on PSW350 subwoofer

[jlewis]

Help! The volume knob on my PSW350 subwoofer has completely broken off and I can’t adjust the volume anymore. Photos can also be seen at: http://nomoon.org/misc/psw350/

This is a $2 part and should be easy to replace with a few minutes of soldering. However, Polk doesn’t sell individual parts, though they will sell me a whole new amp assembly for $200. I called customer support and spoke to a polite person who emailed me a parts list. I was hoping to find an identical part, or at least one with identical dimensions. The replacement part needs to be the same size in order to physically fit. This item (R31) is listed in the Polk factory parts list as "POT, 100KA,9mmx1". However, the part in the list doesn’t exactly match what is in my device. I appear to have a 250K ohm potentiometer. Can anyone identify this part? What does the "9mm" mean? I found a company called "Tawain (Alpha), though their only 250K ohm pc-mounted audio potentiometers were 16mm. This potentiometer is pc-mounted with three solder leads. Does anyone know what company makes this part? Should I assume that it doesn't really matter whether I use a 100K or a 250 K ohm potentiometer? Would one be better than the other? I've been looking at the online Mouser catalog for parts.

I would be grateful for anyone’s help!

Regards,

Jason

http://nomoon.org/misc/psw350/outside.jpg
http://nomoon.org/misc/psw350/back_far.jpg
http://nomoon.org/misc/psw350/back_close.jpg

[F1nut]

Here's thought. Remove the potentiometer, cut a groove in the stub with a hacksaw, re-install it. You can then use a small screwdriver to adjust the volume level. Once you dial it in there should be no need for further adjustments.

[jlewis]

Thanks for the suggestion. Unfortunately, the stub is broken flush with the casing around it. I may be able to cut into the casing a little in order to cut a notch into the stub. However, I don't want to take a chance on damaging the potentiometer further. I have managed to awkwardly make adjustments by using the pointed end of a wood screw.

Jason

[F1nut]

Ok then, in my Mouser catalog on page 537 are three 9mm, 100K PC mount pots made by Alpha to choose from.

[jlewis]

Thanks again for the suggestion. Are you referring to this? (http://www.mouser.com/catalog/628/550.PDF) The audio horizontal PC mount was one of the ones that I was considering.

What are the chances that a random pc-mount 9mm potentiometer will physically fit, i.e., the solder tabs and knob will fit the holes already in my unit? I'll look at the dimensions. I'm concerned that it will ALMOST fit.

Also, do you think that it matters whether a 100K or 250K ohm potentiometer is used? Any ideas on why mine was built with a 250K?

Does the "9mm" refer to how far the knob sticks out?

[F1nut]

Yes, I think 311-1902F will work. If it's not dead on, improvise.

[DarqueKnight]

Find out who manufactures that amp for Polk, then contact the amp manufacturer and ask if they will sell you a replacement part or at least point you to a parts vendor who will.