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I recently bought a Fostex PM Sub-n Subwoofer. I've been having a problem recently where the sub will just cut out. I can solve this problem by turning the volume on the sub all the way up and then turning it back down to the level I would like. It will however cut out again in a few minutes. The entire time the sub is correctly passing through audio.

I have recently discovered that if I keep the sub volume above 50% then it doesn't cut out at all. Also I have noticed that if I press on the volume dial, then it will cut out.

The sub should still be under warranty, but I'd like to avoid shipping it somewhere fore repairs since shipping is expensive and the sub was pretty cheap to begin with.

Any ideas?

kumori wrote:

I recently bought a Fostex PM Sub-n Subwoofer. I've been having a problem recently where the sub will just cut out. I can solve this problem by turning the volume on the sub all the way up and then turning it back down to the level I would like. It will however cut out again in a few minutes. The entire time the sub is correctly passing through audio.

I have recently discovered that if I keep the sub volume above 50% then it doesn't cut out at all. Also I have noticed that if I press on the volume dial, then it will cut out.

The sub should still be under warranty, but I'd like to avoid shipping it somewhere fore repairs since shipping is expensive and the sub was pretty cheap to begin with.

Any ideas?

If you don't have them, find a friend with good soldering skills. The potentiometer used for the volume control sounds like it is flaky and needs to be replaced. Could be simple if they used a panel mount pot with wires running back to the ciruit board. Could be a bit more complex if it is soldered directly to the board along with the rest of the i/o jacks. Order a replacement (Mouser or Digikey is your friend).

--SS

Almost sounds like a cracked solder connection where the potentiometer is mounted to the board. Might be as easy as reflowing the connections. Also, there's a spray can called "tuner cleaner" which is sold by online electronics resellers and RadioShack. It's usually a compound of mineral oil and mildly abrasive silicates, and you simply spray it into the tuner pot and rotate the control knob a few times to clean and lubricate the contacts.

SecretSquirrel wrote:

If you don't have them, find a friend with good soldering skills.

What constitutes "good soldering skills" ? I've soldered the wires on some fans together to run them off the same controller and extended a few wires that wouldn't otherwise reach the motherboard headers in my computer. Anything more complicated than that?

I've looked at changing the volume pot on my amp, but once I opened up the amp it looked like it was soldered to the board and I would need more specialized tools then a regular soldering iron. I'm a little afraid that the sub will be the same.

kumori wrote:

SecretSquirrel wrote:

If you don't have them, find a friend with good soldering skills.

What constitutes "good soldering skills" ? I've soldered the wires on some fans together to run them off the same controller and extended a few wires that wouldn't otherwise reach the motherboard headers in my computer. Anything more complicated than that?

I've looked at changing the volume pot on my amp, but once I opened up the amp it looked like it was soldered to the board and I would need more specialized tools then a regular soldering iron. I'm a little afraid that the sub will be the same.

Most control pots use through-hole connections. Try reflowing the connections; you'll need either some rosin paste flux that you can dip the iron's tip into, or if you don't have that, just dab a little fresh solder on the connection as you heat it, and it should provide enough flux to reflow the connection properly.

The trick with board soldering is to apply the iron directly to the "L" formed by the terminal penetrating through the board so that you heat the terminal AND the pad at the same time. The solder should be nicely liquified all the way around the pad and it will try to "cling" to the metal bits due to surface tension. Then, as soon as the connection has gone fully liquid, remove the heat and let it solidify naturally (i.e. don't blow on it to speed it up).

ludi wrote:

The trick with board soldering is to apply the iron directly to the "L" formed by the terminal penetrating through the board so that you heat the terminal AND the pad at the same time. The solder should be nicely liquified all the way around the pad and it will try to "cling" to the metal bits due to surface tension. Then, as soon as the connection has gone fully liquid, remove the heat and let it solidify naturally (i.e. don't blow on it to speed it up).

There was a time when a company called Heathkit ensured that any and all electronics-minded people knew how to solder.