wmliedtke

The LF10 has a sort of cult following. It was very well received by the audio community and received a ton of praise. It also received its share of complaints, due as I see it, to inconsistent and nagging quality issues. I seem to vaguely recall that at some point, Klipsch recalled (unsold units) of this model and performed needed repairs for chronic quality issues. These speakers were then all resold through a third party and sold "as new", but by a company whose name escapes me. It was like a glorified Ebay, but better known and no auction involved. Goofy name is all I can seem to remember. Hopefully, someone can correct me, fill in the blanks, or tell me I am "totally confused". The later may be the best choice! These are definitely early Klipsch entry into these hi-end subs. Remember you are talking a 20 year old speaker with a dubious history prior to being given to you. Klipsch has some quality subs more current with much higher acclaim and overall review ratings. Sure you know this. Even with my free labor, the cost to repair could become something where you wish you went with a similar, but newer sub-maybe a little less power, but beyond 150-200 watts....they all are *** kicking and sure to anger neighbors!! The spl-120, R-120s, or their newer "C" series. If you are determined to take a deep dive on the LF-10, then couple comments. I hate to make a judgment based upon a picture, but in your pictures you send I see some possible issues: Do I see main filter caps with their liquid guts pooled beneath them? Sure sign these and maybe more are history. If that is all that is wrong in power supply-not a biggie. Also question what copper straps from control board (I assume) have so much oxidation and even appear to be partly eaten away? Could these speakers been in say... a flooded basement even for a short period of time? If so, we may chase one issue after another. I have no way of checking every component in the unit before starting, so I would start with control panel and power supply. I would check filter caps, bridge rectifiers, VRs, other caps, etc. Say I find PS is dead. I replace all bad power supply parts and try unit. I could then find no joy and end-up moving on to say output transistors. Could find them bad and replace. Say I get lucky and unit plays. What if the speaker has limited excursion, an unseen tear, yada yada. Sometimes you just fix first fatal issue you find only to then move on and because you now have a powered unit, you can see other dead stuff you could not suspect until they were under power. Understand? This can be like dominos. My KSPs are not like that as you can replace every component on the board for about 100 bucks should it need all that. Prudent money would probably be on buying new or agreeing to spend X amount on parts in quest to get LF-10s to live again and if you spend X and are not done yet, you lick your wounds and go another way. I will be happy to take in your Sub and do my absolute best using my labor "gratis", but we must have a plan that if we replace say $100 worth of parts and still have a duck, we agree to stop. Personally, I do not see $100 worth of parts NOT getting it done. I just don't want hard feelings because you paid lotta shipping fees, parts, and still have a boat anchor. Think this through well andn don't throw money away you can't really afford to without being upset. Just playing devil's advocate. Too bad you can't go through power supply as that is likely area of most concern and is easiest to troubleshoot. Start with those big filter caps! Then bridge rectifiers. Is relay that takes speaker from standby to "on" energized? If no, why not. Is relay coil power available? Bill

"Do I do repairs for people"? That is a great question, but one that requires a little perspective. The short answer is "yes", but I don't seek out people who need a piece of electronics repaired. Friends, family, fellow ham radio buddies, and the like. I only charge for whatever parts are needed-never my time- and I often have the parts in my "parts bins" acquired over many years and can repair for free or minimal. The downside is that my turn-around time sucks because I rarely return something exactly as received! I have OCD when it comes to I guess you might call "failure mode analysis". Plain language- why did this fail? Seldom do I get those "I dropped it from my balcony" or "I wanted to add this or that to a functioning component and now it won't even turn on"!! If I fix something, I must *try* to determine why it failed and how will my repair not also fail in time as the original did? I must seek a solution such that whatever portion I fix will not come back failing in same manner. I hope this makes sense. I may fix a power supply issue and make my repair as "bullet-proof" as possible only to have the unit fail later...but it won't be the power supply -) Maybe it will be the protection circuit or OP amps in the control circuitry, but it won't be what I fixed or CAUSED by how I repair. This means that if you are in a hurry for a simple R&R job, I recommend friends go to a for-profit shop who will quickly turn-it-around, do little if any root cause, and take your money and you are happy (usually in the short term) that your baby is back home and playing again. This works for a guy whose guitar amp blew the bridge rectifier cause he played it max volume until something had to give or the guy who tried to drive his Infinity tower speakers with an old 25 watt Marantz receiver! Those don't warrant much "why did this happen and how can I improve it". I am not going to redesign the Marantz power supply, up the driver and output section so he can play it even louder and it will fail again at a higher power output! So, when I take something in, I don't promise it back in a week, but will promise it will be repaired with a keen eye on finding inherent weak spots, fixing them right, and while I am in no rush, my price does NOT reflects the time involved! As long as my friends and family understand this, I am all in. The Klipsch P0503 PA board in the KSP400s is not even a good example of corporate "compromise". I love all Klipsch, but can not justify keeping an eye on costs and using marginal components (no headroom in component ratings), extremely poor quality printed circuit board, absolutely no EMI filtering of any kind, and on and on. Virtually even part of the PA section is an accident waiting to happen. Example: These speakers are plugged-in to 110V 24 hours a day, 7 days a week, 365 days a year! Ah, but many would say the standby circuitry effectively "saves" the amp as it is only energizing the output transistors, et al when being driven. Right??? What about the transformer, the bridge rectifiers, the big, but not spectacular filter electrolytics, the +/- 12 VDC voltage regulators, some of the control panel circuitry, etc. No wonder we get premature failure (and hum) due to capacitor failure which is way premature in the whole scheme of things. Power supply may not be delivering its power when in standby mode, but the entire power supply is "alive" 24 x 7 x 365 x years owned! My Denon receiver has both a switched and an unswitched AC outlet on the back. Neither are rated or even sized to power on my KSPs only when receiver is turned on. Why would I want speakers powered-up all the time if receiver is not even on??!!. So, just as our automobiles due, I built a relay box such that when the switched outlet on the receiver becomes active (receiver turned on), the small 120V switched receiver outlet sends 110V to a 20 amp solid state relay in a small box which get its power from the wall outlet and energizes two 120V outlets on box I made. Just as your car headlight switch does not have to be rated for your headlights, taillights, etc., the headlight switch need only be rated and sized to handle energizing a relay coil. My box has two power cords coming out of it and has two 3 prong outlets. I plug box into switched outlet on receiver and main power cord from box goes to wall outlet (or power strip). Bingo! KSPs plug into my box. Conserves amp components, but a side benefit is I eliminate ground loop issue as both speakers get their power from same source and also inside the box is my homemade EMI suppression circuit which gives speakers some protection from noise from ceiling fan dimmer switch (dimmers are notorious line noise sources), Cable TV coax issues, yada yada. Why do we think Klipsch did not even include a single X & Y rated capacitor across the line input?? This would at LEAST be the *appearance* (acknowledgment?) of them considering line noise as a possible issue for a powered audio speaker system! Unbelievable! As usual, too long-winded. Pray someone will get *something* that may help them out of my verbosity! Bill P.S. whether I get a donor amp to play with only means I get to continue to try and make things better than I found them. My speakers will live *forever* (my lifetime anyway) as they get closer and closer to being powered by an amp which reminds me of my Peachtree (Nova 300s). Only problem with these little gems is that they seem to need nothing more from me. I just marvel at how such a small package does so much right. To Carlthess40: what does your sub do or not do, do you have access to schematic you can email to me, and what was going on when it took a dump? Where are you located (don't recognize the lake area) as weight makes shipping a small chore. Maybe I can give you some help depending on your skills and multimeter ownership; at a minimum. Maybe a friend of yours can assist and work with me. Model of sub and age please. I will help if I can. My pleasure. Bill

My fellow forum members, thank you for reading! I have a pair of KSP400s that I have painstakingly re-built and kept working- hum free- since purchasing in 1998! I have had to replace OP amps, power transistors, bridge rectifiers, big CAPS, little CAPS, positive and negative voltage regulators, just to name a few parts to accomplish this. For my trouble, I have 20 year old speakers that work as new. Since Klipsch long ago stopped their factory support for KSP400s in favor of third-party repair shops (no guarantee a "fixed" board will out-live the original).... Here's my end game: I recently retired and an electrical engineer by degree. I am seeking a "working fine business" sub-woofer amplifier board P0503, an amp board with a "bad hum or any other issue", or one that is just plain "dead" and may still be in your junk pile! Maybe you gave-up on these amps and performed an implant of a non-OEM amp into the KSP400 cabinet or you just deleted the built-in amp completely. Whatever may have caused you to have one amp you would part with, I need it!. If yours blows fuses immediately, hums and buzzes and wakes the neighbors, or plays great but is just surplus to your needs....I want it! I will pay fair price depending on degree of function. A good one will become a parts donor or my benchmark to establish test criteria for the "new & improved. Prefer a PA that has "issues" to minimize my out-of-pocket costs and may show me issues with these amps that I have just not encountered (yet). Do NOT feel your amp or control board is "too bad to help me" and the cause. My goal is to re-engineer a replacement amp that can hopefully occupy the stock board size, mounting points, etc.. I will be starting with the OEM transformer and beyond that, I see most all the rest going. My first board will initially be all point-to-point wiring until I get the amp Klipsch wished they built- one that will last, be simple but a brute as theirs was when working, with trouble-free longevity. It would be great to have a spare CONTROL PANEL as well, but I have had very few issues in the control panel to-date and that will be my next undertaking when I get the amp right. I may have to get a control panel-- depending on the PA board design changes-- to send proper control voltages, "auto on" control feature, and the like. Right now, I would settle for the PA board if a control panel is not forthcoming. Once finished with a fully functional PA board that I have tested and am 100% confident will perform well against current state-of-the-art amps, I will breadboard and then make a new circuit board to compliment my amp. My goals are that my board will be plug and play (fit existing space, heat sink, use existing control cable, very possibly use your existing control panel and will have equal or better RMS output and response characteristics than the OEM. I am a tad skeptical the existing control panel will be left untouched as I intend to use a 3 prong plug again and solve ground loop issues. Worst case is that oem control panel will have modifications that anyone handy with a solder pencil can facilitate. This entire undertaking MUST be an improvement without sacrifice in any respect to original. This is a totally NON-PROFIT under-taking!! I will sell just circuit boards alone at cost with a parts list and sources for all parts, and a detailed schematic. Any part I use WILL be readily available via Ebay or MOUSER electronics (worst case). Decent single-purpose amps such as these are easy and relatively simple with minimal parts. I envision the main PS filter electrolytics to be most expensive component on my board at under $10 (assumes you have oem transformer from your old board). Will try to allow using as many Klipsch oem board parts as possible for those willing to swap from their P0503 boards (as long as design is not compromised). I love a challenge, retirement leaves me too much time on my hands, and I have been more of an electronics "tech" than an electrical engineer since age 8; when I became an advanced class ham radio operator and built the first of 60+ Heathkits--- until Heathkit went belly-up. I worked 280 countries with equipment that I made "homebrew". I built many 2000 watt linear amps from scratch as my license allowed over the years, but most of those 280 countries were gotten on my QRP (under 1 watt) gear. Sorry, don't want to digress! Just to illustrate I am not new to making my own solutions and feeding off the results. The number of us who enjoy working with electronics from scratch to a fully functioning "finished product"-is dwindling. Help me fill my days, have fun doing it, and providing back to other Klipsch aficionados. I see no reason why this undertaking should take more than *maybe* 6 months-start to finish. I reside in Lafayette, IN. so you probably know what great engineering school is in my backyard to help with circuit board etching, modeling services, expedited non-destructive (I hope) testing, etc.! If anyone has the ability to DONATE a PA board or control panel, I will see that you get first consideration on any new solutions for PAYING IT FORWARD. Thanks all... for reading and any help, in advance. Bill P.S. prior owner of pair of K-horns, series II Cornwalls, and a few Synergy series surrounds, etc. My kids all have systems to kill for as I wanted to give while still alive to see their awe! Oldest son even got my Macintosh amps to go with the K-horns. Apartment life on fixed income is a *****...

Certainly age of caps is a factor, but I must say that I have MANY electronic components far older than these speakers were when they failed and they just keep on rockin'. If electrolytics had a useful life of 3-10 years, we would all have obsolete electronics everywhere. I have a 50+ year old Macintosh amp that I have never had to open. Why do we think that might be? It is my opinion (just my .02) that the issue is a combination of marginal engineering and under-rated components. When you have speakers that sold well north of $1000 a piece, I see no reason to put 16V electrolytics in a constant 12V environment to live day in and day out. Headroom is everything in this world!

This is my first and only post on a very old and kinda sad topic, but as I looked for my solution I realized that there might still be some interest in solutions as well as my perspective (I'm a retired electrical engineer). To say that the KSPs are not a part of Klipsch's "greatest moments" might be an understatement. This series has been fraught with issues revolving around the amp for the 15" subs since their introduction. Suspect many owners have either given-up, swapped in another amp into the KSP's carcass, or parted ways with them! Some, like me, may have persevered and actually solved their problems. I have gone through several iterations of a re-build on mine over the years and had to do so without the benefit of a schematic; which I now have thanks to one being posted online by a kind member of this forum as well as writing to Klipsch directly and obtaining a copy. It would have been invaluable on my earlier rebuilds which involved replacing OP amps as well as the power transistors. Hum was only a nagging, intermittent issue partly solved by the deletion of the ground lug on the power cords. This is an extremely POOR solution to a ground loop problem that Klipsch should have seen coming. Granted, when new, my KSPs did not hum with the ground intact, but that issue really reared its head as they got older. OK, so what did I find that might help someone else? First, you do not need to be an electrical engineer or electronics tech to bring these speakers back to life w/o a hum! But, you better be damned good with a 40 watt solder pencil! The great news is that all the parts you need can be had on Ebay... probably cost $40 total for both speakers and I have extras of many parts. You can "cherry pick" which parts you try, but I suggest all of these or you may not solve the issue or may have to go in again just to save a few bucks. The amp design is marginal at best. These components are really under-sized as spec'd by Klipsch and I will get into that. Also, be VERY, VERY mindful that the tracings on the circuit board are meant for initial assembly by Klipsch and are easily torn from the circuit board. You may remove a capacitor (for example) and install a new one and flow solder that appears good only to power-up and nada! Visually verify that the trace copper on the board is still there and verify each connection with a multimeter. I used the extra lead length of the new components to "bridge" to the nearest circuit path. This is especially true of power transistors and regulators. Ok...the meat: Replace C4 & C15 6800 uF electrolytic capacitors with bigger (if possible) and 100V rated. I found 10,000uF @100v in 35 x 70mm package- audio quality 4pcs for $29 on Ebay. 80V rated caps have barely 12% "headroom". No wonder they puke their guts in short order. Ditto for C3 & C5 rated at only 25V and C9 & C10 rated at just 16V. I replaced with 35 V for the few pennies they cost over their predecessors. While I was at it, I replaced 7812 & 7912 with L7812CV and L7912CV rated @ 1.5 amps ea. I believe original plain 7812 & 7912s are rated at just 1 amp. Replaced D1 with a 50V bridge rated at 1.5 amp vs. 1 amp incumbent. Just a side note.....My 55" Samsung TV as well as tens of thousands of other Samsung models had a chronic failure where they would not turn on every time after often less than a years use! They used measly 16V electrolytics which failed almost their entire model sequence of big screen TVs when the solution would have been to install even 25V caps. Space was NOT an issue. They saved probably a dime per TV set sold. The denied most repair claims and just google Samsung TV won't turn on to get a scope on the size of the issue. Sure, a 16V cap in a 12V environment *should* work......YMMV. Emphasis on should. One power surge and these marginal components give-up the ghost in everything electronic. All to save $.05 times a 100,000 units sold and failing.... Kinda puts the price on brand reputation IMO. I digress. The parts are so easy to find and cheap the point is not "why" should I replace them, but why not? I did both speakers for around $40 total in parts and I will not have to worry anymore unless output transistors go again...But, at 65 years of age, I rarely risk my ear drums any more 😃 Also cured my "auto" light being on with no drive from my receiver. I cannot reiterate enough that after un-soldering and re-soldering components on these boards that you absolutely verify that the original circuit board foil remains intact. If there is any doubt, use new component legs as "hardwire" to make sure connections are maintained. Just because your solder bead may look shiny and bright, does not mean there is any foil left under the solder bead to make connection "go anywhere". Really hope this helps someone. I tried to attach the schematic pdf here, but keep getting upload error. Maybe I lack privileges. File is only 780kb?? May try in a sep. post. KSP-400 Service Manual PDF.pdf