Update: I replaced the failed IRFZ14 mosfet and changed the two famous capacitors mentioned several times here and the SUB started playing again. I don't have a function generator, so I piloted it with a voltage taken from the attenuated output of a generic power transformer, here the mains frequency is at 50hz. Increasing the volume, however, it went into distortion, I could not understand if it was vibrations of the woofer or distortion of the amplifier. Since I had also ordered the remaining capacitors of the power supply (total cost less than 10 euros) and I replaced them all, including the main one at the output of the rectifier bridge of the mains voltage, in total 8 capacitors, but the problem remained the same . So I investigated with an oscilloscope, which in the meantime I had obtained. I noticed that on the outputs of the TL084 integrated that drive the driver stage of the power mosfets the signal level was different, indicating that the gain of the final stage transistors is not the same, perhaps due to the replaced mosfet which is not perfectly matched. with the others, in any case the feedback on the operational compensates and this would not be the problem. When I turn up the volume a lot and it starts to vibrate / distort, the waveform I see at the output is regular, a sign that the problem is not the amplifier but the woofer. It could also be normal and that it is a limitation of the woofer. I wait to buy a heatsink to add to the existing one to close the sub, because I noticed that what is there, the simple "L" wing, heats even with the woofer in standby, I recommend it to anyone who will try their hand at the repair of this poor amplifier, in addition to safeguarding the transistors, also makes the neighboring capacitors heat less, extending their life
I'm jumping in to an old thread, @wiseoldtech. Hope you might still want to discuss this. (First post on this site so ...)
I have a Polk PSW-110 subwoofer failing with the dreaded "heartbeat". After much searching, I found your post about replacing the Polk plate amp in the enclosure with the Apex MS 8A. Unfortunately, Steve at Apex Jr informs me that he no longer has the MS 8A. Do you have another recommendation for "a decent plate amp" that might work with my existing sub?
Good work mate. I have worked on a few of these Polk plate amps and 90% of the time I find bad mosfets and caps Replace them and usually you’re good to go. But it sounds like maybe you have another issue as well. Please update us when you find it.
Your “heartbeat” problem is likely due to bad caps. I suggest replacing them all. Have seen this problem very often.
If Steve's out of those amps, oh well.
Those are as reliable as all hell.
If you can find a "real" type plate amp that's powered by a "real" power transformer that's rated for 100W, and NOT one of those crappy SMPS supplies, then go for it.
I recently worked on a psw111 and had an issue with it not going into standby mode automatically after 10-15min without signal. In troubleshooting it I discovered that it would pull 9 watts while in standby and also 9 watts with it powered on but without input signal. So the standby is pretty much useless. Like you said, it is a good idea to physically power it off when not in use.
When I replaced the sub with the apex amp, it used about 50 watts in standby.
Typical of transformer-powered circuits.
So I modded it with a tiny additional transformer with a time-delay that kills power to the plate amp after 5 minutes of no audio.
The result is that the tiny transformer only uses 2 watts when in standby.
Typical of transformer-powered circuits.
So I modded it with a tiny additional transformer with a time-delay that kills power to the plate amp after 5 minutes of no audio.
The result is that the tiny transformer only uses 2 watts when in standby.
Finally, I replaced the Mosfet IRFZ14 and all the power supply capacitors, circled in red the notorious bad boys, then the others, I spent less than 10 euros using FR or FC series from Panasonic (but the important is they will be other brand no made in china, with low impedance 105C) and added a heat sink using one made from an old Slot1 processor. As you may have also noticed, the PSW110, and similar PSW111 and so on, always stay on, so I bought a 5V relay and mounted it inside a PVC box, I connected a wire to the relay coil with a connector, one of those circular standards for DC power. To give voltage to the coil I can use either a small 5V power supply to be connected to the amplifier service sockets, sockets that I have on the Sansui integrated amplifier, or, if it has no service sockets, as on the Onkyo AV tuner, I have also purchased an adapter cable that draws 5V from the USB socket and terminates in a circular DC power connector. The alternative simply solution is using a multi-socket extension cord with master switch for the AC power, for both the amplifier and the sub, and switch both off when not in use. I think now the SUB will last longer than me.
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Looking at youtube, somebody mount a 100W Dayton Audio SA100 Plate Amplifier or others. Anyway, if you replace the capacitors, as I have explained previously, you will spend few dollars and SUB will come back as new.
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I buy these POLK junk subs on ebay. I have a PSW10 and an XT-12 . The amps are ALWAYS blown. Drivers are not bad (XT-12 driver is outright beefy).
Since I build amps , I put "Badgers" in them with real a toroid trafo. Never , ever an issue after doing this. They also sound WAY better with a real amp.
OEM = scamerica junk.
Ha !! I just looked at a Dayton sa-100. 1 pair to-3P = 100w ?? What a tiny EI trafo. 100w pmpo BS. Glad I make my own amps. My PSW-10 has 2 X MJL ON
to-264 outs and a 200VA toroid. I consider that a 70W amp. My XT-12 , I'm presently building a 2 pair to-264 with a 300VA trafo ... I consider that a 120W amp.
Since I build amps , I put "Badgers" in them with real a toroid trafo. Never , ever an issue after doing this. They also sound WAY better with a real amp.
OEM = scamerica junk.
Ha !! I just looked at a Dayton sa-100. 1 pair to-3P = 100w ?? What a tiny EI trafo. 100w pmpo BS. Glad I make my own amps. My PSW-10 has 2 X MJL ON
to-264 outs and a 200VA toroid. I consider that a 70W amp. My XT-12 , I'm presently building a 2 pair to-264 with a 300VA trafo ... I consider that a 120W amp.
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Through the years, I've silently watched the "wattage specs" degrade into pure lies.
Lordy knows we're fed lies from just about anything these days.... and yes, politics included.
Back in 1980, a Pioneer SX-1250 put out 165 watts/channel...honest watts.
Now-a-days, with the dumbed-down society that believes anything spit at them, they see a spec, and accept it, even if it's BS.
And how could they despute it?....... they can't, won't bother, they're too busy living their lives from some cellphone "app".
Lordy knows we're fed lies from just about anything these days.... and yes, politics included.
Back in 1980, a Pioneer SX-1250 put out 165 watts/channel...honest watts.
Now-a-days, with the dumbed-down society that believes anything spit at them, they see a spec, and accept it, even if it's BS.
And how could they despute it?....... they can't, won't bother, they're too busy living their lives from some cellphone "app".