Infinity PS-12 Powered Subwoofer Fired Amplifier

[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.

[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.

[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

[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?

[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

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

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

[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.

[MobileXT]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I also notice that my PS12 came with 47uf/16v cap at C37 according to schematics 220uf@16v..

[AresROC]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I also notice that my PS12 came with 47uf/16v cap at C37 according to schematics 220uf@16v..

Since C37 is timing calculated with the value of R121, I found the following info that might be helpful:

Version A - C37 220uF x R121/2.2M = 484
Version B - C37 47 uF x R121/ 10M = 470

I would replace the C37 caps with a value similar to your version.

[AresROC]

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.
[/I][/B]

Love the information here! I was able to repair one of my two PS-12 with the information provided!

I bought a pair of PS-12 in 2006. It's now 10 years and I found out both of them are somewhat dead... x(

The left "L" Sub is 6 month newer than the right "R" Sub by manufacture date, and uses Su'scon 85 degree c main caps. One of them has failed, with a bulged top. The older "R" Sub uses Samxon 105 degree c main caps and they are Ok after I replaced the standby caps C2 + C4 & C9.

I replaced the newer "L" sub with Nichicon 3300 uF 80v 105 degree caps, but it is still having an issue. It would play bass fine for a while, and then after 30 minutes ~ 1 hour, it would start to make cliping noise as if the amp is running out of power. My "R" sub runs fine during those bass passages.

I thought replacing the bad Su'scon caps with Nichicon caps would have solved the issue, but it did not.

Anyone have an idea as to where to start to troubleshoot? I have a cheap oscilloscope that I don't know how to use much, lol. Can a bad transistor exhibit the symptoms above?
https://photos.app.goo.gl/OiIMrbh2b4mdidWD2

[Moreno83]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Maybe the other caps are failing also? They dont need to be bulged to be defective.

[AresROC]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I will go ahead and replace some other caps.

http://www.avsforum.com/forum/113-su...values-me.html
From the above thread, it appears the screeching sound others and mine are producing when first powered on is produced by the crossover caps.

I found them on parts express and will be replacing them, unless someone can tell me the film caps would be a better replacement:
https://www.parts-express.com/68uf-1...citor--027-336
https://www.parts-express.com/47uf-1...citor--027-332

I also purchased a capacitor tester, so I can test each cap's ESR once I build the tester kit. I don't understand why caps would go bad with a high ESR... can someone enlighten me or point me at the right direction? I am hoping not to have to repair this pair of sub woofers again in 10 years xD.

[AresROC]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

My PS-12 has a revision "D" board, which is a design between the PS-12 service manual and the PS210 Sub. From there I compared the design changes and found a few interesting tidbits.

C65, a capacitor near the IR2111 IC was 470uF/16v, it has been changed to 47uF/16v.

C39, C75 was listed as 33uF 16v parts. But in the schematics they were 22uF 25v parts.

I am hoping to "upgrade" some of the parts. C2 is a part that caused the Sub not to turn on from Standby, and it is a 4.7uF/50v part. The 50volt part is interesting since the power supply rail I believe is 15 volt, and the outputs are 72 volts or so. I changed C2 to a 4.7uF 400 volt part, hopefully the C2's capacitance have not decreased too much if it is only getting 15 volt.

BTW, if space allows perhaps C6 & C8 3300uF caps can be a 100volt part or greater? I measured 72 volts on them with 80 volt rated caps.

[AresROC]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

gonna have to replace all the caps.
last 3 of these i did needed all of them replaced.high esr.

^^^^^This. Took most caps off except the output filtering 4.7/6.8 uF 100v bi-polar caps and measured them with a tester.

Most are high ESR and many are just very dead. Gonna upgrade most from 16v to 25v Caps if I have them.

Planning on leaving the 4.7/6.8 uF 100v filtering caps as is (C72, C73). Will map out a sound pressure map with my Radio Shack SPL meter. If they are off I might replace them too... Turning out to be a big project x(.

More excitement to come...

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Just use good quality low ESR cap with 105c rating, no need to go from 16V to 25V.

[AresROC]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Just use good quality low ESR cap with 105c rating, no need to go from 16V to 25V.

Seeing most badly damaged caps are 16 volt parts (36~150 ohm ESR, 10%+ vloss), I did replace them with 105c high temp caps when possible.

Took off the C72,C73 output filtering BP caps and tested them. 0.4 ESR & 2.3% vloss, still serviceable I think but I replaced them anyway because my new caps are 0 ESR and 1% vloss.



This amp design doesn't seem to have a resistor divider/capacitor to minimize pop at turn on. On my unit "R" it turns on to green LED but had an audible "beep" in addition to the relay click.

On unit "L" the AC detection circuit doesn't seem to be working even with a new C2 4.7uF 200v.


The amp turns on fine after flipping the AC switch to on, when not connected to the speaker. When connected to speaker, flipping the AC switch would only go into standby Red LED.
However it does turn on with an audio signal... The Learning continues...

[AresROC]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

[AresROC]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Wow, got it pretty much figured out finally!

Replaced Q2 & Q3. Clean bass all day long! See my fixes here: http://zenlog.wordpress.com/2017/11/...-repair-ps-12/

One lingering issue remains. My right sub turns on to standby mode. Left sub turns on to ON mode right away. The service manual actually doesn't say which mode it should turn on to. Not a big issue...

Very tempting to upgrade this Amp from 150 watt to 250/500 watt

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

You cannot just upgrade the amplifier without upgrading the power supply with it.