Infinity PS-12 Powered Subwoofer Fired Amplifier

[Asimo5000]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Great wealth of information on this thread. I was trying to troubleshoot with DMM and I couldn't locate some of the components, I would like to point out some are on the back of the PCB, especially the smallest kinds.

In my case I have owned this subwoofer since about 2008 (PS12). I didn't have issues until after 2014 I would get a chirp on startup. This progressed to clickiy standby especially in movies where the bass wasn't requested. Fast forward to late 2022 the sub no longer would do anything and would only click.

Today I spent the day troubleshooting the circuitry, suspecting the big caps were bad as many others did, however voltages all appear to be in check. The only thing I can say with certainty is there is a residue around AC1/AC2/AC3 leads that is sticky, also the board gives off some heat in similar area. Voltages seemed OK, resistance OK, voltage on downstream circuit +15V I measured +14V. I could see a changing voltage (AC) when measuring the output speaker leads.

In my case, I suspect it actually is the driver. The driver doesn't move or make much noise when using 9V battery. However it is not open loop, and impedance is fine at ~4 ohm. I am not sure how to verify either amp or driver.

I will see if I have leftover car speakers that I can run off the amp for quick test. Other than that I am not sure what else to do, I no longer have car amps that I can use to test the driver

Any thoughts?

[momaka]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Should I just start replacing caps anyway?
I get nothing out of it at all, have never seen the woofer move.

Yes, start by replacing all of the small electrolytic capacitors, and with good brands if possible. At this age, the old ones are very likely on their way out, given the brand they are.

Great wealth of information on this thread. I was trying to troubleshoot with DMM and I couldn't locate some of the components, I would like to point out some are on the back of the PCB, especially the smallest kinds.

In my case I have owned this subwoofer since about 2008 (PS12). I didn't have issues until after 2014 I would get a chirp on startup. This progressed to clickiy standby especially in movies where the bass wasn't requested. Fast forward to late 2022 the sub no longer would do anything and would only click.

Today I spent the day troubleshooting the circuitry, suspecting the big caps were bad as many others did, however voltages all appear to be in check. The only thing I can say with certainty is there is a residue around AC1/AC2/AC3 leads that is sticky, also the board gives off some heat in similar area. Voltages seemed OK, resistance OK, voltage on downstream circuit +15V I measured +14V. I could see a changing voltage (AC) when measuring the output speaker leads.

Hi Asimo and welcome to BCN.

Given all the people that have fixed these subwoofers by replacing the small electrolytic capacitors, I would say do this as well for your first troubleshooting step. Just because voltages appear OK on a multimeter does not mean the caps are doing their job. Ripple and noise will not show on a multimeter, nor would the internal leakage of a cap in a signal path (unless you remove each cap and put on a leakage test circuit to verify.) These are usually what tends to kill hot-running subwoofer amp boards. So plan on replacing every small capacitor and some of the medium ones too. Only the big ones are less likely to fail... though not always.

In my case, I suspect it actually is the driver. The driver doesn't move or make much noise when using 9V battery. However it is not open loop, and impedance is fine at ~4 ohm. I am not sure how to verify either amp or driver.

The driver is easy and you don't need an amplifier for that.

Just grab a 20-35 Watt 120V (or 230V if you have 230V mains) incandescent/halogen light bulb, or 15-35 Watt corded soldering iron, or even a 10-15 Watt hot glue gun would work. Disconnect woofer driver from amplifier board completely (both leads). Then, using jumper leads, connect one terminal on the woofer to Neutral and the other to one side of the incandescent/halogen bulb mentioned above (or soldering iron or hot glue gun.) Now *carefully* wire the other side/lead/terminal of the incandescent/halogen bulb to 120V AC live (BEWARE that you're working with AC Live here, which can be DANGEROUS and lead to electrocution, so that's what I mean by be careful.) Essentially, you're putting the light bulb in series with the speaker to limit current / power going to the speaker driver so that it doesn't burn out. Once wired up, the circuit will look like this, where "unit to test" corresponds to your speaker driver. At 10-35 Watts (depending on light bulb or soldering iron power rating used), beware that you would get quite a bit of sound and movement from the speaker. In fact, it's a good idea to keep it in the cabinet/enclosure for this test (and screwed in) to prevent bottoming out in free air. Definitely DO NOT use a bulb or iron rated higher than 40 Watts. If this test doesn't make some noise, your driver may be faulty.

Alternative (and much SAFER low-voltage) test for the woofer driver:
using a pair of sacrificial / cheap ear buds or other headphones, remove the headphone drivers / buds and use the cord with the 3.5 mm jack to connect the woofer driver directly to your phone or PC (or other device with sound output.) 3.5 mm audio jacks typically have very limited power, so you won't get much sound from the woofer, but you should still be able to hear whatever your playing (alas very mid-range-y and probably muffled-sounding.)

My personal suspicion is your speaker driver is OK. The amp, I can't say. But with very old electrolytic caps on the board, I'd say the amp is probably OK too, and it's just the old caps causing the issue (hence the suggestion to start with the recap first.)

[Asimo5000]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Thank you for the reply, I’ll start by verifying the driver since it’s a simpler step before going for capacitors

To find adequate replacement Caps, do I just need to match the voltage and uF rating? I didn’t see other specs listed on the existing caps

[momaka]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Thank you for the reply, I’ll start by verifying the driver since it’s a simpler step before going for capacitors

Sounds like a reasonable place to start.

To find adequate replacement Caps, do I just need to match the voltage and uF rating? I didn’t see other specs listed on the existing caps

The voltage and capacitance (uF rating) are the main parameters, but there are a few more that you may need to match (or exceed in superiority.)

For starters, the temperature rating: if the original caps are rated only for 85C, then they are general purpose (GP) caps, and indeed matching only the voltage and capacitance (uF) rating is usually adequate. If the caps are rated for 105C, they may or may not be low-ESR type (actually, low impedance.) For low ESR type, you have to check two additional parameters of the original caps: their ESR (impedance) and ripple current (RC). This you can get from the datasheet of the original caps by looking up their brand and series. But beware that this could turn out into a wild goose chase, as some obscure and/or cheap cap brands may not have published datasheets or incomplete data sheets. For the ones you can find datasheets, though, note the impedance and ripple current for each cap type you have. Then make sure the replacement caps have the same or lower impedance/ESR and same or higher ripple current.

Is it critical to match the ESR and RC rating?
- No, most of the time.
This being a subwoofer, the caps are probably regular GP type or "entry-level" low ESR at best... so should be pretty easy to find replacements.

With all of that said, here's the easier way to go about finding replacements: just use entry-level low-ESR caps for every cap, and it should be OK.

Since you're in the North America, my suggestion is to order online from reputable websites, such as Digikey or Mouser, and use only Japanese brands (Rubycon, Nichicon, Panasonic, and United Chemicon / Nippon Chemicon), since these are the most reliable electrolytic cap brands.

Each cap brand has a series. Different series have different ESR and RC ratings. Here are some series from each Japanese brand mentioned, which should be OK for this type of use (amplifier / audio):

Rubycon YXJ, YXH, YXF, ZLJ, ZLQ, ZLS, ZL
Nichicon PS, PM, PW, HE, HD, HW, HV
United Chemicon LXV, LXY, LXZ, KYA, KYB, KY, KZE
Panasonic FC, FM, FR, FS

These may also work OK for general purpose 85C or 105C caps:
Rubycon: PX
Nichicon: VR, VZ, VY
UCC: KMG
Panasonic: EB, NHG, M-series

And for audio path circuits only (i.e. not part of the power supply filtering):
Nichicon: FW, FG, KW, KT, KA
^ Note that these audio caps may be more expensive. While they are recommended (by cap manufacturers) for use in audio path circuits, they aren't necessary. Any GP or entry-level low ESR series will do OK in audio path circuits too. According to the cap manufacturers, though, these audio caps may be better for the audio quality... but this being a subwoofer, it shouldn't really matter, since you're only dealing with LF (low frequencies.)

[Jodeanss]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Thank you for the reply, I'll start by verifying the driver since it's a simpler step before going for capacitors

To find adequate replacement Caps, do I just need to match the voltage and uF rating? I didn't see other specs listed on the existing caps

you can check that sub with any of the channels from the receiver?? I assume your hooking this sub amp up to something? Sub output of receiver? Use any of the 7 speaker outputs on that to test woofer.

[Asimo5000]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

you can check that sub with any of the channels from the receiver?? I assume your hooking this sub amp up to something? Sub output of receiver? Use any of the 7 speaker outputs on that to test woofer.

True ! Forgot that can work lol

Let me check its impedances on my receiver

[time4this]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

PS-10 here with the C71, C72 issues. Thanks to everyone who has contributed to this valuable repository of knowledge! Amazing.

Has anyone figured out why C71 flames out? What causes this failure mode? I've read through the pages here and don't seem to find anyone elaborating on the causes of this condition. I've got parts ordered to replace, but I'd like to know it is not going to happen again. I'm also going to put a couple air holes to allow some convection (hopefully) to occur. Fingers crossed.