Noisemaker Volume Switch Repair

The Equipment:

Homedics SS-2000 Deep Sleep Sound Spa noisemaker – on loan from my dear mother

The Problem:

Potentiometers rely on moving contacts that do a lot of rubbing back and forth over their lifetime. With enough wear, this can create dead spots where continuity is diminished or even interrupted between the moving contact (known as the “wiper”) and the resistor track.

We sometimes leave the noisemaker on overnight to perpetuate the illusion in our son’s mind that things are still going on while he sleeps, something he grew fond of while in the hospital. And because of the wear in the volume adjuster, we had a hard time setting it to volume level that was not too quiet and not too loud and not in the middle of a dead spot. Worse still, sometimes while playing, the sound would briefly cut out entirely and junior would miss it.

I had enough and found exactly the same switch on Amazon for cheap.

The Plan:

Repair the volume adjuster knob on the noisemaker with a new power switch and potentiometer combo.

The Parts:

10 Pieces D Type Rotary Carbon Film Potentiometer 50K Ohm with Switch – $4.62 from Amazon (link broken as of 1-2-18! I haven’t been able to find a new replacement yet.)

The Process:

Teardown was quick. Four screws out the bottom of the noisemaker and we’re in. Another four screws held the main PCB to the upper half of the clamshell case, and there was enough slack in the wires to gain easy access to the opposite side. The knob disconnected from the base-bone, and the base disconnected from the switch-bone (a little glue and a little screw).

Desoldering the five pins from the PCB was a little more intensive. I didn’t realize at first that the larger power pins were in fact riveted to the board, so my initial attempts to pry the pins away with the tip of my pencil iron were fruitless. But the nice thing about rivets is that they drill out easy, and once they were gone the switch began to loosen up.

Here I made another mistake. I pushed the switch all the way through without watching what was happening on the other side with the pins of the switch still partially soldered to the traces. So it came to pass that the solder pads delaminated from the the board. This blog’s namesake strikes again! Fortunately the traces did not break, so I could continue on to heat and free the pins.

The new switch soldered in without incident. I began measuring resistance on the potentiometer pins to check my work, and also happened to check across the pins of the switch when it was open. What I found was not OL on my meter like I expected. Instead I got continuity, but something like 5 MOhms for resistance. Practically an open switch for this application, I thought, but disturbing nonetheless. I removed the switch again, and tried a another one. Same result. Of course my new switches did not conduct in the open position apart from the board, but for some reason when I placed them in-circuit, they did. File under “But It Still Works, Right?”, I guess, because yes, it worked. I snapped the case back together and we’ve been enjoying white noise consistently at precisely the amplitude our little hearts desire ever since.

Review:

“If at first you don’t succeed, redefine “success” and celebrate your victory!” Comforting guidance for the little politician in all of us. ’nuff said.

Not a bad little product

When all you have is a screwdriver, every problem looks like an oyster.

Dual purpose power switch and volume adjuster knob

Notice the rivets holding the two power leads to the PCB. I had to drill them out.

Just a little screw-on baseplate for the knob to sit on.

Baseplate removed. Indented lettering reads D50K.

It took a little time with the solder sucker and 25W pencil iron to clean the blobs off.

Almost off

Too much force! The traces began to lift off the board when I pushed the old switch through.

Comparing the two switches

New switch in place

New switch soldered down flat. No rivets this time.