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Attn: Technical gurus amp assistance needed!


anarchist

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Ok, I have a set of KSP's and after many years on this forum, I have gotten to see what the inside of a electrolytic capacitor looks like after going up in a poof of smoke. Given the age of these speakers, I suspect some of the other's may want to go as well after this one is replaced. The other speaker is functioning fine however it has now developed a bit of a hum in it that appears to be exactly the same as the hum that was in the other prior to its blowing this capacitor.

So my question is two parts:

1) Should I replace just this one, or all of them on the board, or specific ones?

2) It would appear this is (was) a Nichicon. Does the cap quality make any difference on this board given its function? Is so, suggestions for replacements?

Here is a reference to the schematic and cap values used. The one that blew was the 25V 100uf which is numbered C26.

I appreciate any assistance. Its been a while since I have done any upgrades or repairs - although I did just rebuild a PS3.

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I don't claim to be a guru, but I CAN say I've both installed and extracted and replaced hundreds of electrolytic capacitors in amplifiers and preamps that I have built or repaired for others as well as myself. The quality of the capacitor in the C26 position is not in my view of much concern, and I don't think it's necessary to replace every electrolytic cap on the board at this stage, but if it were mine and the other caps were installed in positions that enabled straightforward replacement without potentially damaging other parts, I'd consider it. I guess I do have some concern about why it blew in the first place, and I would personally want to take voltage and resistance readings throughout the amp. Regarding the hum you're hearing - it could be caused by a number of different things, including aging/faulty ripple filter capacitors after the rectifier. If you do replace C26, it's a very, very common type to replace. Match value of capacitance, voltage rating, overall size and spacing between leads (if it's a radial capacitor) so the through-hole connections on the circuit board fit the cap appropriately. NOW: if you are not familiar with working with potentially very dangerous voltages, DO NOT attempt to work in an energized amplifier yourself. Also, filter capacitors in power supplies can store high voltages for days, even when the amplifier has not been used. You should always (safely) discharge storage capacitors before working in an amplifier. Do Not discharge capacitors the brute-force method, which can be damaging. Sorry - I have to mention the safety element. It's extremely important -- hence the skull and cross-bones shown in the manual.

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If it was me I'd replace every single capacitor in it including the film caps. I would upgrade not only the quality of the caps but in many cases with the electrolytic caps the uf value as space allows (if the caps purpose is related to power supply filtering). I would also seriously consider replacing the OP amps IC's I would not be surprised if one of those went with the cap. Now keep in mind I'm strictly a tube technician and the SS world is foreign to me. If you want someone to send this to let me know.

Basically if one cap has failed they all are in question. The only hitch here is did a cap fail from its own demise or did something else cause it to fail. In most cases in my limited experience with SS amplifiers failure is most likely a cascade effect......

Posting from my droid so formatting will be non existent. I can not wait for the forum upgrade

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The hum in the sub amp of those speakers is quite common from what I've read. A popular repair is to eliminate the sub amp all together. Make a plate with wire terminals to cover the hole where the plate amp was and use outboard amplification. Most that have done this mod like the sounds of the speaker better than the stock configuration.

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Thanks for the replies. Let me give some background on these. When I bought these, they were dead silent. I was thrilled I didn't have the dreaded KSP hum. Initially, they were wired with just speaker wire and had a line-in to the LFE input. For a long time, they ran fine. Then a new pet decided to chew on the line-in cable. I removed the cable. In time one speaker developed a hum, and I unplugged it until I could determine where the hum was coming from; the other speaker provided good bass from the subwoofer and I never thought about it for a very, very long time. Bought some new stuff and decided to run new wires to everything and noticed the subwoofer wasn't plugged in. Plugged it in, had a hum, hear a pop, and had a puff of smoke in my face. Pulled out the control board and found the cap's cap sitting on the bottom along with a bunch of paper and foil. Others have reported this same cap being found in the bottom of their speakers. My concern is the other speaker has now developed this funky hum... its not continuous, it cycles on and off at times... and I question whether its going to do the same.

From my reading, it appears lytics have a shelf-life and have issues with not being powered for a while and then suddenly being powered on and the result is what I experienced. Given that, I questioned whether just to replace all these lytics and of course their effect on sound.

I did contemplate replacing them with non-lytics and was concerned about any effect these might have on sound, but given the board size and lack of space on it, I think I will just order all the cap values listed on that board and replace all the lytics with new ones while I have it out - several of them ARE supposed to affect hum. Screw it.

Nichicon, panasonic... think it makes a difference? I just pulled up these on mouser. It interests me because the cap that exploded has the usual 100uf, 25v marking but also has "SOUND" marked on it and I am sure it was a Nichicon. These Nichicon on mouser are marked 'audio' and show less 'leakage current' than the KT series - not that I even know what that means. But.. to simplify things Nichicon KT vs KA for those in the know?

My only point about the 'sound' marking is I think that would indicate these need to be audio grade capacitors and not just your run of the mill Radio Shack or Chinese junk capacitors; it may, of course, just be marketing nonsense which I why I defer to you guys.

PS. These parts are on the 'control board' where all the inputs are coming in and not on the amplifier PCB; I don't plan to touch it.

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If one were going to go to the trouble to replace ICs, every single capacitor (my opinion differs with concern to film types), etc. another solution would be to replace the amplifier. Working on PCBs like this can be problematic, particularly if one doesn't have practice. And if one then takes it to a tech who charges by the hour, cost of parts, shipping, and labor would probably be more than the cost of a brand new replacement amp. With certain kinds of parts, one also must consider static precautions. Kevin: there are different ways capacitors can be discharged, some of which much preferred for sensitive circuits than others - one of those being discharging through an appropriate power resistor that is aligator-clipped into the circuit (which is NOT) the brute force method I mentioned.

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Panasonic makes low-inductance electrolytics, and I have used them with good success in the past. If you would like more audiophile approved brands, I'm sure you can find the necessary values from Cerafine and Blackgate -- it's possible to dig those up if you look around a bit. BTW: If I remember the schematic right, there is a resistor in series with C26. It might be good to have a close look at that part, as well. To see if a certain resistor is still close to its rated value, it sometimes helps to remove one end from the circuit before connecting your multimeter. When resistors age they can often drift up or down from spec. and subsequently cause problems elsewhere, such as the damaged cap.

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Ok, trying to expand my mind here a bit. Looking at schematic, C26 is on the speaker level low input. I believe you refer to the resistor on that input labeled R53 which is a 680 ohm 1/2 watt metal film resistor, yes? I could order those pieces as well although I would like to skip a complete rebuild.

Here is a stupid question... these things are on speaker level input... in my fantasy world, I could just use the line input and ignore the problem on the speaker level input and all would be good. This won't work because the speaker level input connects to the line level input at R7, is that correct?

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The hum in the sub amp of those speakers is quite common from what I've read. A popular repair is to eliminate the sub amp all together. Make a plate with wire terminals to cover the hole where the plate amp was and use outboard amplification. Most that have done this mod like the sounds of the speaker better than the stock configuration.

I would go with this approach. It may cost a bit more, but it sure would be less hassle than to source and order parts through different online sources, desoldering, cleaning up the PCB/PCBs, soldering in the new parts, and then taking a chance to see if it will work again.

Get a plate amp for each speaker, and run each dedicated sub with them. You probably wouldn't need much power, so a guy could get a lower powered plate amp for a cheaper price. Most have a external crossover in the amplifier, allowing for a bit of tweaking.

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The hum in the sub amp of those speakers is quite common from what I've read. A popular repair is to eliminate the sub amp all together. Make a plate with wire terminals to cover the hole where the plate amp was and use outboard amplification. Most that have done this mod like the sounds of the speaker better than the stock configuration.

I would go with this approach. It may cost a bit more, but it sure would be less hassle than to source and order parts through different online sources, desoldering, cleaning up the PCB/PCBs, soldering in the new parts, and then taking a chance to see if it will work again.

Get a plate amp for each speaker, and run each dedicated sub with them. You probably wouldn't need much power, so a guy could get a lower powered plate amp for a cheaper price. Most have a external crossover in the amplifier, allowing for a bit of tweaking.

You don't have to get 2 plate amps. Just make blank plates to cover the holes where the old amps were. Install speaker wire terminals. You can then get a 2 channel amp with DSP and have better than stock performance.

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Thanks guys. Variety of opinions on this. I would like to keep them 'Klipsch' speakers as designed so decided I will try the "fix it Tony" approach first (used to own a FIAT Spyder.) I can replace 90% of the caps for $15.00 with the Nichicon KA's. Worse case scenario I am out $15 and an hour or two soldering and then move into modication mode if it doesn't bring it back to life.

I would like to get these up and running cheap primarily because I would like to build a DIY sub using a couple 15's or 18's and will need an amp for that. Dropping money into fixing these speakers takes away from that project and my desire to acquire some other new equipment as well.

I will let you guys know how it goes. I will place order with Mouser tomorrow.

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Thanks guys. Variety of opinions on this. I would like to keep them 'Klipsch' speakers as designed so decided I will try the "fix it Tony" approach first (used to own a FIAT Spyder.) I can replace 90% of the caps for $15.00 with the Nichicon KA's. Worse case scenario I am out $15 and an hour or two soldering and then move into modication mode if it doesn't bring it back to life.

I would like to get these up and running cheap primarily because I would like to build a DIY sub using a couple 15's or 18's and will need an amp for that. Dropping money into fixing these speakers takes away from that project and my desire to acquire some other new equipment as well.

I will let you guys know how it goes. I will place order with Mouser tomorrow.

ATA BOY

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  • 4 weeks later...

Update: Replaced caps on the control boards and amp boards. Easy peasy. Dead silent. Only issue was after fixing the one speaker - that was still working - flipped in on and heard absolutely nothing. Reviewed my work a couple times. Everything was good but the speaker wasn't playing. Remembered a post by fini. Pulled the subwoofer itself out and found it had been disconnected when I pulled the amp out to put in caps. SOB. Anyway, KSP's in the house and both subs firing. Klipsch should make these speakers again.

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Update: Replaced caps on the control boards and amp boards. Easy peasy. Dead silent. Only issue was after fixing the one speaker - that was still working - flipped in on and heard absolutely nothing. Reviewed my work a couple times. Everything was good but the speaker wasn't playing. Remembered a post by fini. Pulled the subwoofer itself out and found it had been disconnected when I pulled the amp out to put in caps. SOB. Anyway, KSP's in the house and both subs firing. Klipsch should make these speakers again.

That deserves a second ATA BOY!

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  • 5 years later...
  • 11 months later...
On 10/24/2013 at 5:47 PM, anarchist said:

Update: Replaced caps on the control boards and amp boards. Easy peasy. Dead silent. Only issue was after fixing the one speaker - that was still working - flipped in on and heard absolutely nothing. Reviewed my work a couple times. Everything was good but the speaker wasn't playing. Remembered a post by fini. Pulled the subwoofer itself out and found it had been disconnected when I pulled the amp out to put in caps. SOB. Anyway, KSP's in the house and both subs firing. Klipsch should make these speakers again.

Anarchist would you send me the parts list you ordered to repair your amps. My 400s have been down for 10 years and I would love to them rocking again.

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