Time for a new subwoofer? PSB Subsonic II help needed

[fameless]

I have a PSB Subsonic II subwoofer that I use for HT duty. It has developed an audible hum that gets louder as the days pass. PSB has a replacement plate amp for about $387US. There is a electronic repair shop nearby that charges $75 just to look at something and find the problem, plus the cost of parts and labor so who knows how much it will be. I'd hate to get rid of the thing. Is it time for a new sub? I have also considered using a standalone amp.

 

[Jim Griffin]

You could purchase a new plate from a supplier like Parts Express or Madisound or such and renew your existing subwoofer. A quick look at a photo of your PSB sub shows a very basic amplifier so you can easily replace it and have the same or more functionality. You can review the dimensions of possible replacement amps versus your current unit to ascertain which plate amp would best replace your old one.

Likely you will have to modify your enclosure to accommodate the new plate amp. What I have done is to remove the old amp and then change the cutout to fit the replacement amplifier. A cut here or there or a few pieces of MDF glued in place to fit the new amp would be the job you would face. A little finishing work on the enclosure can restore your sub to its previous functionality.

 

[frankm]

I have a Subsonic III that developed a hum. The hum would disappear if you touched the plate of the amp. I replaced the two prong power cord with a three prong, grounding it to the chassis ground and the hum disappeared.

I have also read that since these amps have no on/off triggers they tend to be powered on continuously. Eventually the heat build up causes the power supply caps (which are placed close to the transformer) to drift resulting in a hum.

Frank

 

[mlipovitch]

I could use a schematic for the PSB Subsonic III or II (same amp I think) mine is currenty working but some burnt resistors that I cant determine the values, they don't test open in circuit but values might be off...driver was blown also so I replaced with a TC Audio driver I had lying around ( the original was a cheapo stamped steel sub cone blew right off the basket..oh well what can I expect for $12 from GoodWill)?
Marc

 

[Chris_wen]

The used PSB Subsonic II I bought soon developed unacceptable hum. After replacing the two 47 uF capacitors, the hum was greatly reduced. However, when listening carefully, the hum was still there. Measuring other electrolytic capacitors, I found that all 10 uF capacitors are bad with only about 5 uF of capacitance and have 15% of voltage leaking. I will replace all these bad capacitors when I have time.