Glotz Posted March 8, 2022 Share Posted March 8, 2022 Hi All, My LF-10 subwoofer quit working and it appears to be the switching power supply module. I do not have a schematic. The green LED comes on when the power switch it turned on or when the switch is in auto and a signal is applied. The relay on the rectifier board kicks in and is supplying 161 VDC to the "PRI DC IN" terminals on the switcher module. I assume this is the unfiltered, full wave rectified voltage. The "SEC DC OUT" terminals on the opposite side of the switcher module read 0 VDC. What limited trouble shooting I am able to do without a schematic found two resistors that were bad. A 100k ohm in the collector of a PNP transistor was open and a 110 ohm resistor in the base read 989 ohms. I am assuming these two resistor and the PNP transistor are part of the pulse width modulation circuit driving the FETs used for swithcing. Replacing both these resistors did not change anything. Can someone please provide some assistance in getting this fixed. I would hate to see it go it the trash pile. Thanks for your help, Warren Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 8, 2022 Author Share Posted March 8, 2022 There are no burned or broken parts that can readily be seen. No swollen or leaky caps. All diodes I was able to check with a diode meter seem to be ok. The PNP transistor seems to be ok. I don't have an oscilloscope. glotz Quote Link to comment Share on other sites More sharing options...
jjptkd Posted March 9, 2022 Share Posted March 9, 2022 15 hours ago, Glotz said: Can someone please provide some assistance in getting this fixed. I would hate to see it go it the trash pile. Thanks for your help, Warren If you've been happy with the sub and can't figure it out maybe add an external sub amp? 1 Quote Link to comment Share on other sites More sharing options...
Deang Posted March 9, 2022 Share Posted March 9, 2022 This has got to be a record for a Klipsch powered sub. 1 Quote Link to comment Share on other sites More sharing options...
captainbeefheart Posted March 9, 2022 Share Posted March 9, 2022 You can't test many of these in circuit, you need to pull the mosfets and check them out of circuit. If you are trying to troubleshoot in circuit you'll most likely need a scope to look at what's going on. Typically the capacitor that gets charged up takes some serious abuse and they fail regularly but so do the mosfets. If you don't use a scope you'll most likely need to pull parts and test them out of circuit. If caps are out just replace them. You'll probably see the mosfets are blown. As I said if you try and test in circuit it's nearly impossible to get the charge off the gate and it will always just show a short, out of circuit you can short the gate to the source with anything and then test drain to source and make sure it's open circuit, place a small charge on the gate, just enough to turn it on and then test that it indeed is showing continuity from drain to source. You'll most likely see that after you short the charge off the gate capacitance you'll still have continuity between drain and source, this means it's shorted and junk. 1 Quote Link to comment Share on other sites More sharing options...
Deang Posted March 9, 2022 Share Posted March 9, 2022 Hey, let's put the amplifier inside the most volatile place on the planet. It's amazing they last as long as they do. Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 10, 2022 Author Share Posted March 10, 2022 Thanks for all replies. Yes, this LF-10 has taken a lickin' and kept on tickin' ... until now. Bought it on 12/31/01 for $575. One 10" speaker and two 10" passive radiators. I ordered the FETs and the PNP this morning. Should have them in two days. I plan on pulling the parts and testing them as the Captain suggested. I will keep you updated on the progress or lack there of in the next few days. Since no one mentioned having a schematic I assume there are none available for Klipsch gear??? Thanks, glotz 1 Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 10, 2022 Author Share Posted March 10, 2022 Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 15, 2022 Author Share Posted March 15, 2022 So this is where I'm at... I have pulled the MOSFETs and they seem to check ok in a simple test circuit, biased on and drawing current, 260 mA, not a lot. The two transformers don't seem to be open, there are 9 terminals on the inputs and 8 terminals on the outputs. There is a device, no markings, that looks like a small signal diode without a cathode stripe. I am assuming it is a Diac used in the PWM circuit. (See photo) Diode check shows an open in both directions probably because it doesn't produce a high enough voltage to turn it on... or it's open. Some of these operate in the 30 - 70 breakover voltage range so I'm going to have to come up with a supply high enough to turn it on. Maybe a bunch of 9V batteries in series. Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 15, 2022 Author Share Posted March 15, 2022 Please comment if you have any suggestions! Quote Link to comment Share on other sites More sharing options...
Jedster1 Posted March 18, 2022 Share Posted March 18, 2022 (edited) I have a suggestion!! 🤣 Abandon this project and sell me the driver!! I have a perfectly good amp, two radiators, and a driver with a smoked voice coil that drags in the gap. 😔 Oh, and no cabinet. I'm building my own. For the time being the amp is driving a single DefTech 10/10 IW sub just sitting on my workshop counter top. I can only run it at around half-throttle. That little amp has some balls!! But seriously . . . good luck with your project. I hope it works out for you. Edited March 18, 2022 by Jedster1 Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 22, 2022 Author Share Posted March 22, 2022 If I had an alternative I would sell. 😊 If I don't get it fixed (receiving remaining parts today) I will use an external amp to drive it. I don't need much in my music studio, just enough to be able to hear the low end during a mix down. Of course I'm going to have to buy a replacement for my surround sound entertainment system. Any suggestions for the sub for a surround sound entertainment system??? glotz Quote Link to comment Share on other sites More sharing options...
Jedster1 Posted March 24, 2022 Share Posted March 24, 2022 (edited) You'll get it fixed. 😉 I've had really good results driving my subs with any old Carver or Adcom amps bridged to mono. I have an '01 Sunfire True Subwoofer Signature that has a blown amp that nobody I've taken it to seems to be able to (or wants to) fix that I've driven with an A-500X, an M-1.5t, a PM-350, an Adcom GFA-555 (all bridged) and a GFA-565 dual mono. They all drive it pretty well, the A-500X being the current workhorse. I also have an Outlaw 770 that won't drive it, so there's that 🤣 It's plenty loud for home-theatre with any of those, so for music and what you're looking for I'd imagine you could drive it with anything comparable. Have fun shopping!! Or better yet . . . . succeed!! Edited March 24, 2022 by Jedster1 1 Quote Link to comment Share on other sites More sharing options...
Jedster1 Posted March 25, 2022 Share Posted March 25, 2022 (edited) Having re-read your query for suggestions I realised that I didn't really answer your question 🤣 I haven't actually witnessed this first-hand, but I'm told that a pair of SPL-150s are AWESOME to behold!! As in blow your hair back and rattle the walls. The C-310ASWi look like a pretty good approximation of the LF-10, albeit with a bit less power but a smaller footprint. I haven't auditioned those either. Edited March 25, 2022 by Jedster1 Quote Link to comment Share on other sites More sharing options...
jjptkd Posted March 25, 2022 Share Posted March 25, 2022 20 hours ago, Jedster1 said: I've had really good results driving my subs with any old Carver or Adcom amps bridged to mono. I have an '01 Sunfire True Subwoofer Signature that has a blown amp that nobody I've taken it to seems to be able to (or wants to) fix that I've driven with an A-500X The Signature plate amps push roughly 450-475 watts RMS according to Bill Flannery the later versions used very thin PCB boards which have a tendency to warp and fracture traces due to heat exposure making them very hard to diagnose and fix with any certainty of future reliability. Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 26, 2022 Author Share Posted March 26, 2022 My first post here was March 8th. Due to lack of the proper equipment (oscilloscope) I have not been able to properly troubleshoot the power supple so I am going to get on with life and just drive the LF-10 enclosure with an external amp. I'm not one to give up such an endeavor but can only do so much with a digital multimeter. ☹️The enclosure may last another 20 years? I guess I've gotten my money's worth! Thanks to all for posting you thoughts, tips and tricks. And as they say, "Keep listening... you may hear something". glotz Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 26, 2022 Author Share Posted March 26, 2022 That's... "Keep listening... you may ear something" Quote Link to comment Share on other sites More sharing options...
Jedster1 Posted March 26, 2022 Share Posted March 26, 2022 22 hours ago, jjptkd said: The Signature plate amps push roughly 450-475 watts RMS according to Bill Flannery the later versions used very thin PCB boards which have a tendency to warp and fracture traces due to heat exposure making them very hard to diagnose and fix with any certainty of future reliability. Yeah, that's the general consensus. Anything built later than '99 isn't worth fixing from what I was told even before I talked to Bill about it. 24 minutes ago, Glotz said: My first post here was March 8th. Due to lack of the proper equipment (oscilloscope) I have not been able to properly troubleshoot the power supple so I am going to get on with life and just drive the LF-10 enclosure with an external amp. I'm not one to give up such an endeavor but can only do so much with a digital multimeter. ☹️The enclosure may last another 20 years? I guess I've gotten my money's worth! Thanks to all for posting you thoughts, tips and tricks. And as they say, "Keep listening... you may hear something". glotz Nice talkin' to ya Glotz!! Good luck, and let us know if you ear anything new!! 🤣 Quote Link to comment Share on other sites More sharing options...
Jedster1 Posted March 26, 2022 Share Posted March 26, 2022 (edited) Yo, Glotz!! I don't know how much you wanna spend but I just ran across this on eBay. Not quite as much ooomph as the original but it might be an acceptable replacement. https://www.ebay.com/itm/Klipsch-Subwoofer-Amplifier-SPL-120-Amplifier-Only-/284673824909?hash=item4247e1d88d Or this https://www.ebay.com/itm/Klipsch-SPL-150-Amplifier-1067491-AMPLIFIER-ONLY-/265577007452?hash=item3dd59f895c Edited March 26, 2022 by Jedster1 Quote Link to comment Share on other sites More sharing options...
Glotz Posted March 28, 2022 Author Share Posted March 28, 2022 Thanks for the input, but in reality I don't want to put too much money into it. There is really no way of telling how long the driver will last after 20 years of use. LOTR blew the voice coil cover loose on the front of the driver a few years back but I was able to glue it back on. It's been working fine but you never know when that voice coil will start scraping... 🥴 (I hate that sound) Glotz Quote Link to comment Share on other sites More sharing options...
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