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WANTED-- KSP400 PA board- DEAD OR ALIVE!!!


wmliedtke

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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 *****...

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"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

Edited by wmliedtke
fix ambiguity
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Thanks Bill

I will email Klipsch about the schematics I haven’t been able to find one online and as for shipping ,of course that’s on me

why or when the problem happened, I don’t know and this is how I received it

The power light turns on and there is zero sound or noise in the sub when it’s turned on

I do have a two channel scope and a few meters. My knowledge is very limited on how to use the scope as I only bought it for setting my gains for my car amps to find when it get to the level of distortion

I just ordered a new meter that will be able to test resistors and capacitors as the ones that I have now cannot do that and it’s the LF-10 sub

Here’s a few pics

c6414e28c179c24a0ecac3674b14d347.jpg25c0b244232148549c10a7eb3afb3842.jpg9cdab7b3c088a4334192dd539e9d8154.jpge99b3c482150bb50f27aa38fd23ed198.jpgca2f9464a65b4103f018db342b846a8a.jpg32ee757e0d71350bccab036486388a83.jpgc0c8c41860545aa073fc8f6a33ae3734.jpg0c1ba0a4daaceb84834c17755dadba8a.jpg3dcb230581576ee00d0290e3d43bc37b.jpg

 

 

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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

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Thank you bill
I just got a new meter in and will start testing some of the places you pointed out
I did see the green on the copper bars , I don’t see any water marks anywhere else
I’m in Florida and the Humidity is always quite high and the guy told me that the service been in his garage for 12 to 15 years or so ,so I’m sure that has come from sitting unused for many years
I did not notice the caps , I’ll look at those closely and see if I can measure them but I will try to clean everything the best that I can and start doing what measurements I can without taking it all apart
I greatly appreciate your time and effort and patience and looking at all the pictures I sent you


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I now see that 3 of the power caps are bad. Large bulge on the top of them
I have 115 plus dc going into that top board and only 0.256 dc coming out on the other side
I can hear the relays turning on when I turn the power on
As for all the golden gooey stuff around the bottom of the caps I thought was glue that they use to hold them in place for vibration they seem to be evenly spread around all six of those caps but none of the other caps on any of the other boards have this gooey stuff on them.
Later I will pull the power board off and try some more test. I may remove a few of the caps and test them off the board



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