Friday, April 10, 2015

Fixing the Infinity PS210 Subwoofer

Just got a PS210 at a thrift store for cheap; plugged it in and quickly learned why...Googled its name and number plus the word "problem" and there it is; the amp is completely sealed inside a plastic chamber so air doesn't shoot out the RCA jacks, etc. This causes the amp to very quickly overheat and shut off. Right now I've got it playing happily along by removing the amp from the back panel so the tiny heatsink can breathe a minute.

When I first powered it up I experienced the dreaded Standby bug, which is it turning off the instant signal drops below a certain level. This can become oscillation. Haven't had it since removing the power supply from the cabinet. Yes, it's just sitting up against the unit, ugly as hell, so that needs to be addressed...I'm wondering about 1" nylon spacers and longer screws, so it's still mounted to the rear of the unit, but is held out enough to breathe. Ugly, but convenient.

Improvements? Mounting the amp externally with a larger heatsink. Bigger power supply capacitors (Nichicon Super Through if possible). C6 and C8...3300uF 80V. They're tall but thin so fat ones won't mount to the PCB. I like to increase both the capacitance and voltage ratings when replacing caps such as these.

That heat sink is way too small. Might need to get something better and mount the transistors to it off the PCB, requiring a bit of wiring. (This is something which apparently effects the highly-regarded Nakamichi Stasis receivers...the heat sinks don't get to breathe.)

One thing I'm noting is that the crossover frequency pot is intermittent. Its cutoff moves up and down, perhaps in league with the switch which makes it full-range. I note that pushing it a touch past its maximum setting opens it a bit more, when it's "down".

I also note that the mode switches produce a huge LF pop. Very bad. Haven't checked if that's "normal". :p

This is a nice subwoofer although I'm not yet convinced that a smaller, lighter cone isn't better for punch and kick of music versus the sustained LF rumble expected by home theatre enthusiasts.