Subwoofer no longer produces sound

[smbrisbin]

I have a PSB Subseries 200 woofer connected by single RCA to my Yamaha A2060. The light on the subwoofer indicates it has power and signal, however the tone test no longer produces sound. I removed the subwoofer electronics, which consist of an I/O board, feature board, power supply unit, and output board. Application of battery voltage across the woofer leads produces a thump, but touching the RCA jack does not. I suspect something failed on the output board. Any repair or troubleshooting suggestions? Thanks!

 

[TLS Guy]

I have a PSB Subseries 200 woofer connected by single RCA to my Yamaha A2060. The light on the subwoofer indicates it has power and signal, however the tone test no longer produces sound. I removed the subwoofer electronics, which consist of an I/O board, feature board, power supply unit, and output board. Application of battery voltage across the woofer leads produces a thump, but touching the RCA jack does not. I suspect something failed on the output board. Any repair or troubleshooting suggestions? Thanks!

Your best bet is to contact PSB.

Those class D MOSFET amps are a nightmare to troubleshoot and service. I guess PSB and NAD are now owned by the same company.

Usually when these type of amps fail the usual recommendation is to replace the amp.

NAD has acquired the moniker, Not Always Dependable.

 

[smbrisbin]

TLS Guy, thanks for the advice. I've reached out to PSB inquiring about a replacement output board. I confirmed that the stereo produces a tone with a different sub, so it's definitely not a problem at the input.

 

[TLS Guy]

TLS Guy, thanks for the advice. I've reached out to PSB inquiring about a replacement output board. I confirmed that the stereo produces a tone with a different sub, so it's definitely not a problem at the input.

The problem is that you don't actually know the problem is with the output board. Usually with those class D amps it is the switching power supplies that cause trouble more often than not.
Don't forget that a power supply has multiple sections with different voltages and current outputs. Low voltage for the control and voltage amp stages and higher voltages for the output stage.

You need a circuit with voltages marked at the least and preferably a service manual as well.
You also need a high impedance FET VOM as using a cheap multimeter can do damage and give misleading results. Then you need to confirm the stage where the problem starts by tracing a signal from a signal generator and tracing through where the signal gets interrupted.

There are no short cuts to service work and you have to have some experience the right equipment and at least a circuit with test voltage points marked.

So in your case you need the whole amp unit replaced.

I have been down these type of situations with posters before, and so often these type of repairs lead to failure and a waste of money.

After writing this post I see from searches that this amp is a horror story. It is a diabolical contraption that continuously varies the power supply voltage with load. Experienced service people on the DIY forum have had no luck at all trying to repair these.

I have found that PSB will not service them or provide parts only replace the whole amp, which I understand is quite expensive.

These people have ended up cutting their losses and just getting an external amp, usually Crown, and fitting speaker terminals on the back of the sub. Since this is a ported unit, any good external amp of around 200 watts will do the trick.

Realistically your options are to send that sub to the recycling center, or adapt it for an external amp.

Quite honestly the moniker Not Always Dependable is deserved.