Infinity PS-12 Powered Subwoofer Fired Amplifier

[MobileXT]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I have also a Infinity PS12 that won't turn on. The LED is always red. I already replaced capacitors C2,C4,C9, C78 and C12 according to this forum and still have the same Problem. Also I am waiting for the rest of the capacitors to arrive the two NP capacitors. They look good but I will try to replace the two once the NP capacitors arrive.

[molalani]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Thanks for the reply Bud, much appreciated!

I'll check to see what the timing is like the next time I use it and go from there.

Mo

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

C37 is the Timing, the Value will determine how long the unit will stay active AFTER it does not detect the audio signal, the unit should stay on for about 10 minutes (Service manual page 9, AUTO ON/Stand-By) then it will timed out and mute the unit, see SCH PDF page 33.
Service manual Page 8:AUTO ON/Stand-By
The subwoofer will automatically enter the Standby mode after approximately
10 minutes when no signal is detected from your system.The subwoofer
will then power ON instantly when a signal is detected. During
periods of normal use, the Power Switch ¶ can be left on.You may turn
off the Power Switch ¶ for extended periods of nonoperation, e.g., when
you are away on vacation.

[molalani]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

First off, just want to thank everyone on this thread! It's one of the most informative I've read in order to try and DIY a project.

I don't have a tonne of electronics experience, but I took a couple courses in high school and it has aided my tinkering ever since.

I own a PS-10 subwoofer, and I've had the same situation as Derek (DoubleD14) where my board is in perfect shape and no caps look to be swollen, however the light on the back of the sub was constantly flickering between green and red and there was no output from the sub.

I decided to replace all the caps on the lower portion of the board nearest the transformer (C2, C4, C9, C12, C35 and C37), as that seemed to have been effective for most users here. I purchased caps from a local store based on the values in the service manual. Upon removing C37 I noticed that the value did not match what was written in the manual. I removed a 47uF cap, and it is listed as a 220uF, both at 16V.

I installed the 220uF cap anyways, and sure enough the sub works again! Only peculiar thing that I don't remember from before, is that when I power up the sub with the switch, I hear a squeal that lasts about half a second and increases in frequency until it disappears. Kind of sounds like a capacitor loading up. Should I replace with a 47uF cap instead? Could that even be the reason I hear that sound, or is this just a normal attribute of the unit?

I've also noticed that the temp on the back panel where the transformer sits has been super hot, so I'm planning to add a small fan to the back panel with a separate 12V supply, and running the supply through a second almost identical relay in parallel to the one on the board so that the fan only runs when the amp switches on with a signal present. Any downside to this that I can't see?

Also, for anyone who doesn't own the sub, the compartment in which the amplifier sits is completely sealed off from the moving air inside the sub, so there shouldn't be any effect to the acoustics.

I'll also post pictures of the mod when I'm done, although it may not be all that pretty.

Thanks in advance!

Mo

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Start by check the resistance of the rectifier diodes, power output transistors to see if they show very low resistance.
How about the pictures of your boards?

[balboarules]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Hey guys

I have a PS-12, when you plug it in, the fuse instantly blows, where should I begin to troubleshoot that? I have a soldering station, desoldering gun, voltage meter, and some knowledge from working on pinball machines.. I pulled the amp out, put another 2V fuse in, popped instantly when I turned the unit on.

Thanks
Steve

[999999999]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

four3rds, yes that's just glue that turned brown from heat. The way they put the shrink wrap on some caps that size, with the plastic disc on there it makes them look a little domed on top like bad caps get but that's usually just the plastic disc bulged up, not the metal under it.

Trying to describe from scratch how to trace an amp is really beyond the scope of a forum post but basically you whip out a multimeter and see if the right voltage is getting to the output transistor(s) or power pin on an output IC.

With the audio you feed it a line level continuous tone and probe for where the signal (AC voltage) drops out. Since you are getting audio I wonder if it's just a potentiometer with a bad wiper. You could jumper across its pins to see if that produces FULL volume. Feed it a lower signal level in case that would blow the speaker or disconnect the speaker and measure output voltage. If you can't figure out which 2 of the three pins to jumper then you probably should ignore my advice and not be messing with a live mains powered amp, but basically one pot pin is signal input, one is ground, and one is output. Jumper input to output.

If audio signal is making it that far you keep tracing the circuit to the next IC's audio input pin and verify that the audio output pin is outputting signal, and if it's a gain stage then the voltage should be a multiple higher to reflect that gain. You keep tracing the audio AC voltage all the way to the speaker output to see where it's supposed to get gain and isn't, or see where the signal is dropping like if there's an output relay and the contacts have oxidized so it's acting like a capacitive coupling. When tracing you'd get the part # off the component, use that to get the datasheet, and use that to get the pinout for power and audio I/O.

[four3rds]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I have an Infinity PS-12 that's exhibiting slightly different symptoms – the signal detection circuit detects when a signal is present and the light switches from red to green as expected but the sub hardly outputs any volume. This thing should rattle your teeth when it's working properly.

The capacitors at C6 and C8 looked suspicious to me but after doing a little reading that may just be glue that was applied at the factory to hold them in place. So, I am wondering if the experts here have any opinions on how I should troubleshoot my sub. I am not an electronics expert but I can handle replacing the capacitors if they are indeed the issue and I can find suitable replacements. The sub is about 12 years old. It really hasn't been used all that much and it's never been pushed hard – mostly just used for movies and not at some outrageous volume.

Any information/advice will be greatly appreciated.

[DarDar]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Yeaa.... PS12 is FIXED!!! Thanks for the information! Burned it in yesterday with about 5 hours of hard rock thumping! Changed out all caps in high heat area and all Samxon caps. Total of 8! Hopefully I want have to go back in, but it would still be advisable to help solve the heat issue!

[DarDar]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I also have a PS12 which had died a while back. Started off making popping noises on occasion then quit. When I first opened it up I immediately noticed that the C6 cap (3300uF) had a bulging top. (black plastic but definitely pushed up) I made an assumption that was the problem and ordered two new caps. Got them in and swapped them out. When I moved the cap that was bulging back and forth I could feel something inside moving around, definitely not normal so I figured that was the problem. However when I installed the new caps it still didn't work. That's when I searched the net and found this thread! My LED also fluttered between red and green, (95% red). I cranked up the volume and adjusted the bass output +10 db from the receiver and it just fluttered away between red and green (now about 50/50), relay clicking madly. I tried putting an 820 ohm resistor across C2 as suggested in the thread and it went to green. It appears the caps that failed were all SAMXON, so I'm going back with Nichicon. The new C6 and C8 were 25mm instead of 22mm but they fit just fine! You can definitely notice where the board has been heated up due to those 5 watt resistors! So in addition to C2, I'm going to change out C4 and C9 while I'm at it due to excessive heat... and C78 and C12 to replace the bad actors ( SAMXONs)! Soooooo, I have ordered a few more caps and hopefully in a few days I can give you the results!
First pic shows new 3300uF Nichicons caps already in place (albeit tight)! Second photo better displays heat problem!

[hepha3stus]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Hi All,

I hope you can help! I have a PS210 (Service Manual Attached) which will not produce any sound. The power supplies look good, and I have been applying a signal to the Amp, and following it with an O-Scope. Here is where Im at so far:

The signal looks good on side 1 of R84, then is pulled low on the other side side 2. Scope images attached. I dont think the signal should be Low on side 2 of R84 should it? what should I do next?

I am a DIY-er, but am new to electronics and repair, Help is much appreciated!!!

[drakulina]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Well, it was the C2 cap.
Replaced and now the amp works fine.

[drakulina]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

OK, on C2 Voltage reading does not look right.
Do you have 100~1K resistor?
If you do, put the resistor on the two legs of C2 and see if the relay will come on

I am really sorry to revive an old thread, but I have an Infinity PS410 (same amplifier plate it seems as PS-12) with the same fault as DoubleD14's.

I have measured the C2 voltage and it is 5.82 - 6V. It drops to 4.5 V if I manage to make the relay click by setting the plate horizontal with the discrete components on the bottom.

I tried your advice to use a resistor on the C2 pins and the relay clicks nicely and the sub works. I do not understand what component is faulty? The C2 cap?

Thank you

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Yes, any 1/4W or larger will be fine.

[DoubleD14]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I don't have any resistors, where can I buy one locally? Radio Shack?

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

OK, on C2 Voltage reading does not look right.
Do you have 100~1K resistor?
If you do, put the resistor on the two legs of C2 and see if the relay will come on

[DoubleD14]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

How about C2 Voltage s marked in post 56?
https://www.badcaps.net/forum/attach...1&d=1413344894

Also check the DC Voltage on either C71, 72, 73, or 74 to make sure it is not the power amp output is causing the shutdown.

My appologies for the delayed reply, been entirely too busy as of late.
OK got the following results"
C2 reads about 6.25 but bounces a bit to a few tenths above or below that
C71-C74 are all 0.0
Thanks,
Derek

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

How about C2 Voltage s marked in post 56?
https://www.badcaps.net/forum/attach...1&d=1413344894

Also check the DC Voltage on either C71, 72, 73, or 74 to make sure it is not the power amp output is causing the shutdown.

[DoubleD14]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

ok these are bouncing all over the place on both capacitors:
C4 hovers around 14.5
C37 bounces from .4-1.1 or so
LED on unit is still red like its not getting a signal to turn the amp on...so it's not even doing what my initial complaint was, seems worse now. I only took it apart and put it back together

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

OK, then start taking voltage readings, just do not let the probes slip on you.