Have an old Klipsch 4.1 speaker system? Did it die? I bet you can fix it!

Desolder the pot and measure resistance of pins 1 and 3. That will be all you need to find the correct replacement as they are simply voltage divider devices. Pin 2 the wiper divides the voltage drop across pins 1 and 3. If the resistance between pins 1 and 3 is open circuit then you'll have to find another way to determine the correct value for total resistance.
 
I've found that taking the pots apart and cleaning them with electrical cleaner fixes all of my issues. No more crackling, no more weird volume jumps.
 
Just saw this thread pop up. I had a Klipsch Promedia 4.1 set up that I got probably around 1998. The only reason I got it was because when I ordered my Compaq 600 MHz Athlon system through the console at Best Buy, if you added a $249 CD burner option, you could get these speakers for $1. The volume pots wore out on mine. I got the standard pops, dead spots, and static. I actually bought a bunch of pots and I was going to try to replace them. If I remember correctly, one of them was like 1 knob that had 3 or 4 volume pots on the shaft. I was going to have to rewire everything to work out using a bunch of extra pots. I let it sit for a couple of years and eventually just trashed the whole thing and decided it wasn't worth the trouble about a year ago ;-) Right now, I'm running a FIIO preamp into a small amp that connects to two old Sony bookshelf speakers. I don't have a sub, but the main drivers on those speakers are 6 inches maybe, not sure. Good enough for me at this point in my life. I do wish I had had the time and desire to put it all back together. Those speakers rocked.

The 2.1 system on sale on Klipsch's site for $109 right now.
 
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Finding the size pot isn't too hard, its finding the ones that actually fit and are the right size which seems to be the problem. Hell on ebay I can get the Surround and volume pot all day, but the sub one is just, non existent. :/

I did a little cleaner and that seemed to bring the sub one back to some semblance of working so maybe it just needed a little cleaning/lube, but I guess we will see. Mine are the old OG ones without any aux input or power button so the insides are quite simple.
 
x33 said:
Hi guys.

I have just registered, because I felt obliged to give back to the community the same kind of help that I have received by reading the plethora of useful postings including the schematics for our beloved Klipsch.

Here's the story, intentionally both LONG and detailed, for one to be able to follow the logic behind the fix:

I have bought a 4.1 system off Ebay, having the known issue of NO POWER/DEAD.

I have started by checking the two famous-by-now resistors R26 and R12, and although they look a bit "tired" they measure ok on the digital meter. That being covered, I have started checking the voltages or should I say, the lack of them...

I have, obviously started with the DC-DC converter as it was getting the 127vDC from the I/O board, but only 52VDC was coming out...The needed 33VDC was missing completely!

I have followed the schematics and that lead me to find the first victims: C22 and C23 both 47uF/50V. I have used an Capacity/ESR meter and found both completely dead, ZERO.

Replaced them with two good quality Nichicon caps of the value as the original, but rated for 105 degrees Celsius. I am assuming the original ones dried out due to heat, as they were not a good quality anyway (Samxon).

Excited enough, I gave it a test and...NO GO !...The damn 33Vdc was still not present..

It just didn't make any sense, since the schematic is sooo simple on that side...I soon realized that either the transformer is fried or...maybe R27. Actually it turned out to be R27 ! NOTE: on the diagram is listed as 4.7ohms/ 1/2 watt. The color coding on mine said 41ohms, which is non-standard, unless the colors went nuts ! I have replaced it with a 47ohms 1/2 watt.

So, thunderdem0n you were on the right track ! I have replaced it and then just like thunderdem0n said, I have started seeing a bit of smoke coming out and I've cut the power right away...Bizarre. Why would that happen???

Well, keep on reading as it gets really interesting.

I figured that it must have something to do with an excessive load on the 33Vdc rail. Therefore I have disconnected J1 connector that goes to the I/O board. Surprise !!! No smoke and my voltages are normal now !!!

It's time to check the I/O board for culprits: checked all the electrolytic caps on my 33Vdc rail, but all turned out to be in perfect shape (C24,25,26,28,29). Hmmm, what gives then? The U1 and U5 ic's are the next, as they are supplied by +15V and -15V through U2, U3 and U4 stabilizers (which checked out ok too). It was enough to put the meter on pins 4 and 11 of the U1 and U5 to find a resistance of 1ohm across !!! Ahaaaa, gotcha !

While I was preparing to pull these IC's off the board to see which one is fried, I had to remove the 20 pin connector J2 that goes to the Amplifier board. For some reason (luck or inspiration ?) I have re-checked across the pins 4 and 11. Guess what?- the short was gone !!! Thank goodness it's not the I/O board !

Ok, now what ? Time to check the Amplifier board for the shorted component. Looking at the schematics, you'll see that +15Vdc and -15Vdc are powering the ic's U0 and U1 on pins 4 and 8. A quick check with the meter confirmed the short across these pins. Ahaaa, we're getting very close !

Eeny, meeny, miny, moe ?! It would be nice, but we're talking about 10 smd ic's which all looked great, no overheating or smoking signs at all.

Oh well, I've got so far, so I might as well start removing them one by one. NOTE: a heat gun soldering/desoldering station is required for this, otherwise it would be a nightmare..

Don't panic, read on !

After removing all the red/black wires for the speakers, I could see much better the Amp board, and the REVELATION came in all it's intense beauty (yeah right...). I have found the culprits without removing the IC's !!!

It turned out to be 2 tiny brown smd caps C9 and C10 which at a closer look (thanks to my magnifying glasses) were clearly showing a crack through them and signs of overheating !!! They are mounted in series over +15V/-15V rail and they have failed miserably by shorting out !

One mention here: the schematics of the Amp board represents only one speaker channel, so in real life, on the board, you'll see the circuitry x 5 times (one for each speaker), therefore the caps will be numbered as C109, C209, C309, C409, C509 and C110,210,310,410,510 respectively.

In my case, the victims were C309 and C310. It doesn't mean on your board the same ones will fail. You'll have to check them all !

Once I have removed them I could confirm the shortcircuit disappeared.

Since they are not marked and the scematics do not provide us with the value, I have assumed they must be standard 100nF/50V, which are very common- typically mounted across the power pins of IC's. You can find them on a lot of boards that you keep for parts in your closet (at least I do...:)) .

I have replaced them, reconnected everything the way it was, and.....SUCCESS !!!!! Houston we now have ignition ! :cool:

One more word of advice: when you remove the speaker wires off the Amp board, you may want to tie them in pairs (red/black) using some painters tape and write on the tape the designation of the speaker - FR, FL, RR, RL and SUB, otherwise it would be almost impossible to tell which was the original location.

So, to conclude the detective work here's the reconstruction of the "crime":

1- the two electrolytic caps C22 and C23 gradually dried up and eventually they became non-existent

2- the now unfiltered 33Vdc made it's way to the Amp board, where probably a nice voltage spike killed the two smd caps C9 and C10.

3- in return, the caps shorted out the main +/-15Vdc, which overloaded the 33V secondary circuit on the DC-DC board. The resistor R27 was the first to give up acting as a protection fuse...

Please ALWAYS take the necessary precautions when performing any work on the circuits while connected to power, as there's LIVE 110V and even HIGH-VOLTAGE going through the boards = high ELECTROCUTION HAZARD.
Story being told, I'd like to thank everybody for their help with schematics,photos and tips and wish you good luck reviving your Klipsch and I'll be more than happy to answer any related questions.
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Can't tell you how much of a genius you are, your explanations and very accurate description led me to find 2 smd caps C209 and C210 that were cracked and shorted. Had spent hours trying to find the culprit of R27 burning out, and boy was I really far from the solution, but thanks to you, it's back up and running. A million thanks to you X33!
 
Toriessian said:
This forum is populated by actual necromancers. There is no other explanation.
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I hope this thread never goes away for when the next time my promedias get popped by a surge. Or I could just buy a new set for $100.

As far as volume pot crackling and such goes, a little Deoxit goes a long way. Assuming they aren't totally destroyed.
 
Burticus said:
I hope this thread never goes away for when the next time my promedias get popped by a surge. Or I could just buy a new set for $100.

As far as volume pot crackling and such goes, a little Deoxit goes a long way. Assuming they aren't totally destroyed.
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My P/M4.1 have been crackling for a couple years now. Been considering tearing the pod down and looking at the pot and maybe replacing it. Just never seem to find the time. Maybe tonight with some deoxit
 
gwsjr425 said:
My P/M4.1 have been crackling for a couple years now. Been considering tearing the pod down and looking at the pot and maybe replacing it. Just never seem to find the time. Maybe tonight with some deoxit
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There are three common causes for noise, including static, for the ProMedia 4.1, as well as some less-common causes. 1) A failing 50k potentiometer will cause noise, which will be noticeably affected by adjusting volume. This is common for both the main (4-gang) 50k potentiometer, as well as for the Surround (rear) 2-gang 50k potentiometer. I use part P094N-FC15AR50K for the main, and P092N-FC15AR50K for the Surround. Those have an audio taper, and Klipsch seems to have used a non-audio taper, so you may notice volume adjust in a non-linear fashion with those replacements. However, I found that using DeoxIT was only a temporary solution. The modern conductive plastic surfaces in potentiometers simply wear out from use, and cleaners cannot undo the wear that occurs. 2) The adhesive that Klipsch used to mount four ceramic capacitors to the bottom of the control pod's board (only true of the 4.1, not the earlier v.2-400 version) will char from heat and absorb moisture from the air, causing corrosion and even become conductive, rather than remaining an insulator. That corrosion and conductivity can produce noise. The solution is to remove the adhesive, without damaging the copper traces. 3) The NE5532 8-pin preamplifier chips used in the 4.1 (not found in the v.2-400) can fail and cause noise. IC replacement is the solution for that.
Less common causes could be the failure of one of the preamplifier ICs in the amplifier panel itself, though that is quite rare. The power supply section of the amplifier has components (e.g., two 47 uF, one 2.2 uF, two 470 uF) capacitors dry out and lose capacitance, which will degrade performance, though the symptoms can vary. Those parts always are powered, whenever the system is plugged in, so after 15+ years (>130,000 hours), it is understandable that they can be due for replacement. I replace at least 8 components in the power supply whenever I refurbish these systems. (I have kits with these potentiometers and other parts, along with the option to replace the 6.5" 6-ohm speakers' original foam surrounds with new rubber surrounds).
The current $109 Klipsch ProMedia 2.1 uses a far weaker design (TDA7265 chip), so there is good reason for people to preserve these v.2-400 and 4.1 systems which--like the ProMedia 5.1--still have four MOSFETs in the output stage, per channel.
 
I've had my ProMedia speakers packed away for awhile because I've been remodeling my den. I packed them in their original box and stored them in the basement. Not climate controlled but not damp or moist either. I hooked everything back up and had no rear speakers. The front outputs on the box seem to be working as all of the speakers function when hooked to those outputs. I thought it might be a loose connection in the 8 pin connector that goes from the pod to the sub box, but I got good continuity from all wires. That tells me the issue is in the box on one of the boards. Any suggestions on what to check?
 
gwsjr425 said:
I've had my ProMedia speakers packed away for awhile because I've been remodeling my den. I packed them in their original box and stored them in the basement. Not climate controlled but not damp or moist either. I hooked everything back up and had no rear speakers. The front outputs on the box seem to be working as all of the speakers function when hooked to those outputs. I thought it might be a loose connection in the 8 pin connector that goes from the pod to the sub box, but I got good continuity from all wires. That tells me the issue is in the box on one of the boards. Any suggestions on what to check?
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If you haven’t already done so, swap the actual speakers (front to rear, rear to front) to confirm that the speakers themselves work. If all 4 speakers work, great. Move onto the next step. If a speaker doesn’t work then you’ll need to fix it.


Then swap the 2 plugs going to your PC. Make sure that the sound that used to be in the front now comes out of the rears. If it does, then the internal amplifier works. If no sound comes out of the rears then the internal amplifier is the issue. Otherwise move to the next step.

Next, swap the speaker wiring at the sub box. Again, front to rear, rear to front. The rears should be on now. If not, then the wiring between the sub box and the speakers are bad.

These 3 tests should tell you what part of your system is failing. The 4.1s have, IIRC, 4 discreet amplifier circuits plus a combined subwoofer circuit. I don’t have the schematic in front of me but you should be able to look over the amp board for bulging capacitors or burnt resistors (the two most common failures).
 
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