Infinity PS-12 Powered Subwoofer Fired Amplifier

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I decided against replacing C17 and C18 due to their use/location.

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I decided against replacing C17 and C18 due to their use/location.

Huh. My service manual (Rev 1 10/2004) doesn't have a reference to C17, C18. And my board has both of those spots blank.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Interesting. I wonder what else changed between manuals. I'll have to look, but I think mine might 2002 or 2003.

Guess I made a good choice on those 2 caps.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Well duh. In one of my more recent posts I referred to my sub as PS-12. That wasn't actually correct. They are so close I just picked up that label for it. Mine is the Entra Sub Two. The service manual for it is Rev 1 4/2003.

I pulled down the PS-12 Rev 1 10/2004 service manual just to have it.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I just took a quick glance at the service manuals for the 2 subs (Entra Sub Two, PS-12), and they are basically identical with the exception of just a few parts removed. Outside of the few missing, it appears all of the part numbers are exactly same. Sorry for the confusion last night!

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

jiari, I basically ordered the same parts. Should be here in a few days. Then find time to install...

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

jiari, I basically ordered the same parts. Should be here in a few days. Then find time to install...

Yep, it's always finding the time that's the problem. I'm still looking for mine.

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

It's alive.

1st try (still dead): I started by replacing everything except C72 and C73 because, why not. Same problem (no output even though relay clicks and I can verify the relay is working). I verified the rails and they looked about the same (I think one leg was low by a volt). One of the 15V diodes is probably going.

2nd try (worked): replaced C72 and C73. Output seems to work fine. I got this broken off Craigslist for $35, spent another $30 in parts. I don't know what it sounded like before. Compared to my 8 inch 100W sub, this "300W" sub doesn't seem that much louder at 75% volume, though it is a lot punchy-er (ie you feel the low frequency much more). It could also be the setup. The 8 inch is in the corner and the PS-12 is infront of the TV.

I added 3/8 inch standoffs, but the indent of the sub enclosure still blocks any proper airflow. I'll need a fan.

In my setup, the power strip turns on the sub when the tv comes on, which is annoying now as the sub always chirps when it starts up. I checked and it's apparently normal, which makes some sense.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I finished replacing everything I ordered including the new MOSFETs and transistors. I had quite the time getting the heatsink back on due to apparently some binding from heat. The 2 PWB mounting screws did not come out easy. One would not thread all the way down so ended up using some small washers with the felt washer on the bottom. I forgot to thread the thermistor screw back in before remounting the heatsink so it had to come back off due to lack of clearance for a screw driver. The second screw would then not seat although it seemed to thread in okay the first time (remember they both were initially tough to remove). I ended up using a couple ofwashers on it as well for fear a screw would break off or completely spin out if I pushed it. Crazy.

I just quickly plugged in the amp and played a little music and it didn't go up in smoke. The squeal is still there at power on as well. There is a cap mentioned on the referenced blog that can supposedly be swapped out to get rid of the power on squeal. I will need to watch a movie to see if it still goes in and out of standby as low volume.

I need to put the sub back where it was tuned before making a call on how it sounds.

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I finished replacing everything I ordered including the new MOSFETs and transistors. I had quite the time getting the heatsink back on due to apparently some binding from heat. The 2 PWB mounting screws did not come out easy. One would not thread all the way down so ended up using some small washers with the felt washer on the bottom. I forgot to thread the thermistor screw back in before remounting the heatsink so it had to come back off due to lack of clearance for a screw driver. The second screw would then not seat although it seemed to thread in okay the first time (remember they both were initially tough to remove). I ended up using a couple ofwashers on it as well for fear a screw would break off or completely spin out if I pushed it. Crazy.

I just quickly plugged in the amp and played a little music and it didn't go up in smoke. The squeal is still there at power on as well. There is a cap mentioned on the referenced blog that can supposedly be swapped out to get rid of the power on squeal. I will need to watch a movie to see if it still goes in and out of standby as low volume.

I need to put the sub back where it was tuned before making a call on how it sounds.

That's funny. I also forgot to put the thermistor back first. I'm surprised you had such trouble with the screws in the heatsink.

To be honest, I was pretty ready for a bright spark and smoke when I first plugged the AMP in (I tested it a bit first before plugging into the speaker). Glad it seems to be working on your end.

Do you have a squeal or a chirp? My research says the chirp is normal, but not the squeal. The squeal seems to be related to the crossover caps (C72 and C73) [note post 93 mentions them related to the issue), but I think you changed them.

I see the note on AresROC's blog that changing C65 from 470uF to 47uF fixes the chirp. Honestly, I can't tell if it's ok to swap out. The change looks ok to me (IR2111 seems to be used very closely in line with the application notes which only called out the bypass cap), but I don't know amplifier design. AresROC mentioned in post #94 that it was a design change on his revision D board. I'll give it a try if I need something from Mouser. I'm not that bothered by it.

I might spend some time trying to understand why one of my 15V rails is low.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I was also surprised by the difficulty with the heat sink screws. The odd part is it was only the two screws that come through the pwb and not the other sets of screws that hold the clips in place.

How would you define a chirp versus a squeal? If the only difference is duration than mine might be a chirp. It's not very long and it happens as soon as it comes out of standby.

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

How would you define a chirp versus a squeal? If the only difference is duration than mine might be a chirp. It's not very long and it happens as soon as it comes out of standby.

You have a pretty good point. I guess I would say a chirp is shorter than 0.5 second. A squeal is at least a second. I listened to the chirp coming from my subwoofer and it indeed could be classified either way depending on the listener and criteria used. It starts as a chirp and ends in an almost squeal (by my varied definition). I think we both now have functioning subs, which is great.

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I looked at the PS210 schematic which has the same basic layout as the PS12, particularly around IR2111. I'm sure the swap of 470uF (C65) to 47uF will be fine.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I will probably swap it. I already have a couple on hand that I purchased originally to fix the chirp/squeal.

My amp still takes a lot of input before it will come out of standby. Something is still amiss.

Another thing I didn't expect is what appears to be a loss of volume, but at the same time I think it's tighter cleaner bass. Prior to new caps is it possible a whole lot more unfiltered signal was coming through and adding to the volume? I bumped my receiver sub output to +5db from +1.5db, and it is appears to be close in volume to what it was previously. Could the replacement MOSFETS have this affect? I would think so.

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Please let me know if the c65 swap fixes the chirp. I'll probably do it.

As for the MOSFETs, I poured over the data sheets and am sure IRF640NPBF (made by Infineon) is a direct replacement for IRF640N (made by Infineon). You can pull up their data sheets and check yourself. What this means is that outside of the old IRF640Ns being damaged or slowly degrading, the new MOSFETs should not have had an effect on the output.

My understanding is that actual capacitors have a model with resistors in series (ESR) and in parallel (ripple). Hence, as ESR rises, you should get longer response from the capacitors as well as more noise which should result in sloppier bass. I'm not 100% sure that explains everything though.

Tell me more about what it takes for the bass to come out of standby. Remember that what's coming out of your receiver's sub port is a filtered output. So the sub may not be getting any signal until a movie or song hits the right note. My fronts go down to 40Hz. I have my crossovers set at 80Hz on the fronts and 90Hz on the subwoofer (on the receiver, disabled on the subwoofer). If I play a song, the sub doesn't always click on right away. You can further test this by outputting directly (on low volume please) from a source (MP3 player) directly into your sub with LFE turned off. I did this before connecting to my receiver and could clearly hear the music coming through. You can use this same method to test if the detection circuit is working correctly. Just keep the volume low.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Agree on the MOSFETs and capacitors. Both should have only improved sound quality.

The standby issue. My receiver volume level goes from I think -60 to 0db. It takes about - 32db before the subwoofer will come out of standby. After that I can turn the volume back down into the forties and I can still hear the sub responding to input. 32db is moderately loud. I've not had much time to see how long it will stay out of standby at the lower levels. Before replacing parts it would slip back into standby if I watched a movie at lower volumes and when there wasn't much bass for awhile. After this happened it would stay in standby until the volume was elevated to the thirties. Need to watch a movie to see if the latter is resolved.

I'm wondering if increasing the receiver sub output will help keep the sub out of standby since the bass sounds more defined even at lower levels. It doesn't appear to be helping with taking the sub out of standby.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

As for standoffs, I believe I'm using one inch long standoffs with number 6 inch and a half long screws that were pretty close to the original screws in diameter but obviously longer to get through the standoffs. I think this is giving plenty of air gap around the amp. I now have a 50 mm fan mounted inside blowing down on the heat dissipating resistors. I'm getting a little bit of vibration noise that I think I can easily get rid of with a little bit of padding where the fan meets the plastic frame. At the moment I have a 110 to 12 volt LED converter mounted to the back on one of the standoff screws. Not pretty but the back is facing the wall and not the room. It's functional at the moment, and I can improve it later if I feel like it.

[jiari]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

For the standby issue, can you confirm you changed the following caps?

C2, C4, C6, C8, C9, C35, C37, C78

Can you also verify the +15V and -15V rails? You can turn on the amp without the speaker plugged in and just probe the + and negative of C6 and C8.

You can also just completely bypass the auto sense circuit if you want (though not preferred). We should see if we find any other problems first.
I can post a picture of how to do it if you want to go that route. It seems that the signal reaching the sensing circuit is too low.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Yes, I'm pretty sure I got all of those caps. I ended up changing all the electrolytic caps except c64. I meant to change it too, but missed it.

I'll measure the +/- 15v rails.

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

The time constant of C37/R121 determine how long the amp will stay on AFTERr the audio signal is no longer present, the larger the cap the longer it will stay on, the schematic shows 220uF, you can try 470uF for longer ON time.