FIRST QUESTION: Is this posted in the right sub forum? maybe should be in Class D amps?
EDIT NOTE: Please DISREGARD Reply #2 which was incomplete when posted. I cannot edit or delete it so I can't fix my mistake.
Argh!
I have an OLD 1996 vintage MTX home theater 15" powered PS15 subwoofer.
I pulled the plate amp out and there were 4 connectors which appeared to all be different (Right?!?!) - well 2 of them were identical, each a very light gauge coaxial cable that along with another connector go to the front panel which has a 1) LED illuminated volume dial, 2) motor driven volume dial, 3) IR remote port, and 4) a LED power indicator.
The board at the 2 connectors simply say J14 and J15. One cable is gray, the other brown.
The front panel assembly requires removal of the sub to remove (at least that's what I'm guessing because with mirrors to inspect I simply cannot see how it is attached to the case.
WHY would they use the same connector? Could it be on of those deals, "If it doesn't work, reverse them - not unlike LED jumpers on computer motherboards where you flip them if they are wrong polarity.)
Other than trial and error, I figure I need a schematic, help from MTX which frankly they might laugh at me, or someone who knows these units.
I've heard these amps have a terrible reputation, but the build quality looks good to me.
_____________________
And now you laugh at me: I had the sub in the back of a closet and I hooked up my cell phone with a sub tested to sweep it an nothing happened. So I pulled the amp, right?
WRONG!
I didn't realize there were front panel controls, in particular a power LED and a volume knob! I THINK THE VOLUME KNOB WAS AT MIN/OFF POSITION. So it is entirely possible the damn thing works and I just screwed the pooch.
EDIT NOTE: Please DISREGARD Reply #2 which was incomplete when posted. I cannot edit or delete it so I can't fix my mistake.
Argh!
I have an OLD 1996 vintage MTX home theater 15" powered PS15 subwoofer.
I pulled the plate amp out and there were 4 connectors which appeared to all be different (Right?!?!) - well 2 of them were identical, each a very light gauge coaxial cable that along with another connector go to the front panel which has a 1) LED illuminated volume dial, 2) motor driven volume dial, 3) IR remote port, and 4) a LED power indicator.
The board at the 2 connectors simply say J14 and J15. One cable is gray, the other brown.
The front panel assembly requires removal of the sub to remove (at least that's what I'm guessing because with mirrors to inspect I simply cannot see how it is attached to the case.
WHY would they use the same connector? Could it be on of those deals, "If it doesn't work, reverse them - not unlike LED jumpers on computer motherboards where you flip them if they are wrong polarity.)
Other than trial and error, I figure I need a schematic, help from MTX which frankly they might laugh at me, or someone who knows these units.
I've heard these amps have a terrible reputation, but the build quality looks good to me.
_____________________
And now you laugh at me: I had the sub in the back of a closet and I hooked up my cell phone with a sub tested to sweep it an nothing happened. So I pulled the amp, right?
WRONG!
I didn't realize there were front panel controls, in particular a power LED and a volume knob! I THINK THE VOLUME KNOB WAS AT MIN/OFF POSITION. So it is entirely possible the damn thing works and I just screwed the pooch.
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PROGRESS: I pulled the front controls (they were pressed into case - didn't have to remove speaker but I did).
The 2 same-connecter type coaxial cables go to a conventional 3-terminal pot for the volume control. Wired as follows:
Pot resistor goes from terminals 1 to 3
Pot wiper, terminal 2
Wiper on 1 for MIN Volume setting
T1: Shields (both)
T2: Brown
T3: Gray
So the question is: Is the pot wired as a voltage divider? OR a simple variable resistor where the Brown and Shields are the same potential (ground?)
Does the Brown indicate Earth and hence Ground?
The 2 same-connecter type coaxial cables go to a conventional 3-terminal pot for the volume control. Wired as follows:
Pot resistor goes from terminals 1 to 3
Pot wiper, terminal 2
Wiper on 1 for MIN Volume setting
T1: Shields (both)
T2: Brown
T3: Gray
So the question is: Is the pot wired as a voltage divider? OR a simple variable resistor where the Brown and Shields are the same potential (ground?)
Does the Brown indicate Earth and hence Ground?
UPDATE:
I pulled the front control assembly and the coax cables go to a simple pot for volume control.
Letting Pot Terminals T1, T2, T3 defined as:
T1 to T3 is the resistor
T2 is the wiper
T2=T1 at MIN position
Wired as follows:
T1: Shields, both
T2: Brown
T3: Gray
I just did the "truth tables" and it looks like it DOES NOT MATTER which was surprising:
At MAX volume, T2 = T3 => Gray=Brown
At MIN volume, T2= T1 => Resistance between Gray & Grown is the Pot Resistor which also does not change if coax swapped.
CONCLUSION: Either Way Works.
I'd like "Roger" on that, Roger. (Is the World Once Again Spinning on Greased Grooves?
I pulled the front control assembly and the coax cables go to a simple pot for volume control.
Letting Pot Terminals T1, T2, T3 defined as:
T1 to T3 is the resistor
T2 is the wiper
T2=T1 at MIN position
Wired as follows:
T1: Shields, both
T2: Brown
T3: Gray
I just did the "truth tables" and it looks like it DOES NOT MATTER which was surprising:
At MAX volume, T2 = T3 => Gray=Brown
At MIN volume, T2= T1 => Resistance between Gray & Grown is the Pot Resistor which also does not change if coax swapped.
CONCLUSION: Either Way Works.
I'd like "Roger" on that, Roger. (Is the World Once Again Spinning on Greased Grooves?
IT WORKS (WOOHOO) BUT - appears to have misaligned voice coil.
Well, I guess I'm documenting this for maybe the one other guy in history that may have the same problem LOL.
You'll laugh, I have NO room to work on this, so it is all scattered on my bed where I must sleep tonight!
But the Good News is that I hooked everything up out of the case and it WORKS JUST FINE!
But some Not So Good News: the voice coil is scraping, but behaving like it is not centered - if I put pressure on the dust cover of outer rim of the cone, with not much at all, I can get it silent, but where it is now, it buzzes and makes "tones" almost like a sine wave.
I realize the woofer is in free air but that shouldn't matter.
I tried pressing on the magnet structure trying to deflect the basket and I found some sensitivity there. Like maybe make a basket bending tool LOL.
The surround appears to be foam and intact which is somewhat surprising for a 1996 date code. Maybe someone reconed it? If they did, the job was very neat.
One suspicious observation but seemingly irrelevant is that the front flange of the basket has that traditional thick paper gasket that is maybe 1/4" thick. In one place it is "rolled" inward maybe 20*. Why that happened I don't know but in this region the face of that gasket is not flat with the rest of the gasket. I believe that gasket is on top of the surround. Maybe the surround glue is separating there.
But in this region if I apply radial force inward, this produces a greater scraping. So maybe not irrelevant.
The woofer is down firing so there were no asymmetric gravity loads on it over the 20-ish years it was in my closet.
For now, it goes back together and GEE, one SUCCESS is more than enough for a day!
Any ideas on the scraping, I'm all ears. I suspect THIS problem is definitely in the correct sub forum.
Tom
Well, I guess I'm documenting this for maybe the one other guy in history that may have the same problem LOL.
You'll laugh, I have NO room to work on this, so it is all scattered on my bed where I must sleep tonight!
But the Good News is that I hooked everything up out of the case and it WORKS JUST FINE!
But some Not So Good News: the voice coil is scraping, but behaving like it is not centered - if I put pressure on the dust cover of outer rim of the cone, with not much at all, I can get it silent, but where it is now, it buzzes and makes "tones" almost like a sine wave.
I realize the woofer is in free air but that shouldn't matter.
I tried pressing on the magnet structure trying to deflect the basket and I found some sensitivity there. Like maybe make a basket bending tool LOL.
The surround appears to be foam and intact which is somewhat surprising for a 1996 date code. Maybe someone reconed it? If they did, the job was very neat.
One suspicious observation but seemingly irrelevant is that the front flange of the basket has that traditional thick paper gasket that is maybe 1/4" thick. In one place it is "rolled" inward maybe 20*. Why that happened I don't know but in this region the face of that gasket is not flat with the rest of the gasket. I believe that gasket is on top of the surround. Maybe the surround glue is separating there.
But in this region if I apply radial force inward, this produces a greater scraping. So maybe not irrelevant.
The woofer is down firing so there were no asymmetric gravity loads on it over the 20-ish years it was in my closet.
For now, it goes back together and GEE, one SUCCESS is more than enough for a day!
Any ideas on the scraping, I'm all ears. I suspect THIS problem is definitely in the correct sub forum.
Tom
UPDATE: Basket face gasket related to VC scraping
Apply pressure to gasket, combinations of compressing it, trying to slide/roll it inward or outward had a substantial effect on the scraping.
It looks like the gasket shrunk, shear creeped the glue until it hit the surround corner (where the flat glue flange meets the moving "bellows", stopped creepig and then started to roll up against the surround.
Other areas of the surround have a large gap, maybe 3/16" away from that corner.
Now while the gasket fits the basket frame properly, this Zero to 3/16" gap suggest the surround is not center OR the basket is bent. Could it have been dropped? Who knows.
My opinion is that this can be further assess if I can get the gasket off and inspect the surround glue and positioning. At worse, separating the surround flange (if possible) repositioning and regluing OR a new surround.
But for now, Back in Box!
Apply pressure to gasket, combinations of compressing it, trying to slide/roll it inward or outward had a substantial effect on the scraping.
It looks like the gasket shrunk, shear creeped the glue until it hit the surround corner (where the flat glue flange meets the moving "bellows", stopped creepig and then started to roll up against the surround.
Other areas of the surround have a large gap, maybe 3/16" away from that corner.
Now while the gasket fits the basket frame properly, this Zero to 3/16" gap suggest the surround is not center OR the basket is bent. Could it have been dropped? Who knows.
My opinion is that this can be further assess if I can get the gasket off and inspect the surround glue and positioning. At worse, separating the surround flange (if possible) repositioning and regluing OR a new surround.
But for now, Back in Box!
UPDATE: MTX PS15 Subwoofer internal component pics
1996 MTX PS15 Subwoofer (Home Theater) Components - Album on Imgur
1996 MTX PS15 Subwoofer (Home Theater) Components - Album on Imgur