ProMedia 2.1 fried resistor (I think)

[maxcavett]

We have had this speaker system in my class for like 4 years now and we finally hooked them up. The volume control knobs work backwards and the satellite speakers play but with low volume (though the knobs are turned completely to "Min"). The subwoofer does not work at all and only a small click can be heard when the power is turned on. I took them home and took the back off the subwoofer. I looked around the circuit boards and found a fried resistor (or at least I think that's what it is). It is on the board with a lot of large capacitors, and I'm pretty sure it connects R120 with J113. Now I have no experience with internal electronics whatsoever, so any details on what to do will be helpful when asking somebody more professional than myself. Thanks.

[TheNewPorridgeKing]

I have the same situation with the resistor next to R120, Q106 as well as the transistor closest to that large cap. I was fixing the DIN cable and had its pcb removed. With the board removed, I had power and signal -- every appearance that things were fine. As soon as I put it all back together, I had no power. Could this be cause for no power?

[razzz42]

Of course replace the fried one and the one next to it since the values for both are the same but upgrade them to 1 watt (82 ohm). My 2.1 came back to life after I replace those two resistors. So will yours if you are lucky if not you are out the time spent and about a buck in parts.

[DEC]

Of course replace the fried one and the one next to it since the values for both are the same but upgrade them to 1 watt (82 ohm). My 2.1 came back to life after I replace those two resistors. So will yours if you are lucky if not you are out the time spent and about a buck in parts.

I've got the same exact problem with the same resistor. I get what you're suggesting, but is it really OK to move up from a 1/4 watt to a full watt on those two resistors? Would it perhaps be better to split the difference and just go up to 1/2 watt instead?

[razzz42]

Of course replace the fried one and the one next to it since the values for both are the same but upgrade them to 1 watt (82 ohm). My 2.1 came back to life after I replace those two resistors. So will yours if you are lucky if not you are out the time spent and about a buck in parts.

I've got the same exact problem with the same resistor. I get what you're suggesting, but is it really OK to move up from a 1/4 watt to a full watt on those two resistors? Would it perhaps be better to split the difference and just go up to 1/2 watt instead?

stpeteshepherd over at ebay, who knows much more about Klipsch subs than I ever will, suggested the 1 watt upgrade. I've done it about ten times or about 20 resistors without a problem. Listening to a 2.1 right now that I upgraded with (2) 1 watt. I've seen the stock 1/4 wat resistors fried or non-functional or browning the circuit board area it lays on or any surrounding insulation but still working even on subs only a couple months old. I don't really troubleshoot but can solder a bit so I just do as suggested. No problems so far, certainly hasn't hurt anything as for peace of mind that the sound won't degrade over time as the stock resistors heat up and begin to fail and act up.

Sure you can go 1/2 watt if you want. I manage to change out the resistors without removing the circuit board from the panel. Have a dental pick and razor knife of some type at hand to remove any over sprayed adhesive/insulation foam that might be holding then in. I de-flux the soldered area and re-spray silicone on the area. That's probably just overkill on my part. #1 wicking ribbon to remove solder sometimes comes in handy.

Also was told to leave the new 1 watt resistors high (1/4 inch) off the board to help air circulation cool them so I do that too.

It's a fairly easy project, have fun.

[DEC]

OK, thanks. I was really asking this question more out of ignorance (or "blind logic"), but with the 1-watt resistor recommendation you got from stpeteshepherd and the fact that you have done the work with success is more than good enough for me at this point. However, if you don't mind, I would like to ask you some more questions as I am not much of an electronics kind of guy.

1) Beyond replacing resistor R120/J113 and resistor R107/Q106 with 1-watt 82 ohm resistors, it sounds like you have replaced more than just these two 1/4-watt resistors in the ProMedia 2.1 sub (since you mentioned 20 resistors). Is this the case, or did you just replace the same two resistors for other 2.1 subs?

2) While I am mechanically inclined and have several soldering guns (including a couple of variable temp pencil type stations), I have never done any desoldering/soldering on a circuit board. Can you help me a bit on technique? For example, here is what another more experienced person recently suggested to me: "Apply
a small amount of solder to the tip of your soldering iron and then
touch it to the resistor you are trying to remove while pulling on it
lightly with a pair of pliers until the solder melts and it frees the
resistor. As soon as the resistor comes out, blow on the board to help
cool it of since you don't want to burn anything nearby to where you
were soldering. A can of compressed air works well for this. A lower
tempurature soldering iron works well (450-480 degrees) but regular
higher temperature irons can be used, just be carefull not to burn the
board". Would you add (or suggest anything different) to all of that? Also, what are you specifically referring to in terms of "respraying silicone on the area"? What are you using and what does that process accomplish? (And I will definitely get some #1 wicking ribbon).

3) In terms of the new resistors, from pics I have seen on-line, they will probably have rather long leads on each end. Do you snip these off to about the right length before soldering them into the board, or do you solder them in and then snip off the excess from the back side? (No doubt a dumb question).

4) Finally, I have several types of solder, but I often use Radio Shack .062 diameter lead-free silver-bearing solder. Is that a good choice for this job, or should I be using something else?

Thanks in advance for further helping out a "circuit board newbie".

Don

[razzz42]

Actually it's just rhe alike resistors R120 and R113 to be replaced. I've worked on about ten subs equals 20 replaced resistors.

60/40 rosin core is the usual
standard solder and sufficient. Size, I don't think
matters much, you just need to get a glob of solder on your tip then
take it over to and place it on the wire leg and trace hole you are
working on.

Common removal steps would be to grab a wire leg with a tool and heat the solder up from the opposite side of the board until you can pull it through with the tool. As soon as you can see the solder puddle you can start pulling. I do it like that then wick the holes clear of solder. I guess you could pull and heat from the same side or wick the solder completelt away first, do whatever you like.

I guess most guys would just bend the legs to size of the holes and to cut the legs to length desired then reheat the old soldered holes and push the new resistor wire leg back through. I clear the holes usually with wick, bend the legs to fit, cut and leave the legs longs, pass them through the holes and tnen resolder on the trace side of the board. Snip the excess wire off, check my work around the hole maybe touch it once more with the tip.

Resistors can be installed in either direction, the color bands can run either way. But it is good practice is to keep the bands running the same on both.

Silicone Resin Lacquer...is what it says on my old spray can, it's expensive. Circuit boards are spray lacquered after completion for a protective coating. It at least keeps moisture from affecting the connections.

I have a 25 watt, 30 watt (Walmart) and 45 watt (Sears) irons. Use the 25 watt with a chisel tip the most. Also have a solder sucker tool but don't use it that often.

There are no dumb questions......just stupid answers.

[DEC]

Thanks much for all of the valuable information razzz42 ... I really appreciate it! I've now got the 1-watt resistors, desoldering wicking ribbon, and solder on order.

One thing that you said though is definitely a curve ball for me, and that is the identification of the second resistor. On my circuit board, resistor R120 is the damaged one, and the identical 1/4-watt 82-ohm resistor (which is the same size and with the same gold/black/red/gray stripes), is directly adjacent to it is shown as R107 on the back (green) side of the circuit board. Also, when I have traded posts or emails on this subject with two other individuals having the same issue, they both referenced the same R120 & R107 resistor pair. Moreover, take a look at the following schematic where the same two 1/4-watt 82-ohm resistors are labeled as R120 & R107:

In fact, I can't even find resistor R113 anywhere on either my circuit board or the ProMedia 2.1 schematic. I certainly don't want to goof up at this point, so if I am somehow missing something (such as a key resistor location or identification), please let me know.

Also, something else I wanted to run by you to get your opinion on is the following. I did an in-situ resistance check of the slightly damaged resistor
R120 and it read out as 80.4 ohms. Then for a comparison, I did a
resistance check of the adjacent undamaged resistor R107 (which, as mentioned above, is
the same rated resistor as the damaged one), and it read out as 81.2
ohms. As I have already stated, I am no electronics guy, but I was
surprised at how close the two readings were. So here's my question ... do those close resistance
readings imply that slightly damaged resistor R120 is not in that
bad a shape, or is this a case where even a small drop-off in relative
resistance potentially causes deliterious electronic effects &
issues? In other words, does 80.4 ohms versus 81.2 ohms for 82 ohm
nominally-rated resistors fall into the category of acceptable
statistical variation for such a resistor type? If the latter, it
makes me wonder if going to the trouble of replacing the "bad" resistor
is going to gain me anything if it is in fact operating within the
range of its tolerance. On the other hand, maybe "bad things" are happening to the performance of resistor R120 when it heats up during operation (as I tested the resistors when everything was cooled down). Please let me know what you think.

Thanks again!

Don

[Mister_Clean]

This is an Excellent Thread, Keep it going guys! Other people will certainly be looking for this information in the future. This is one of the better Klipsch Forum Threads I have seen.

DEC, Let me know how things work out for you. I am crossing my fingers for you.

[razzz42]

Sorry about mis-stating the number for the location of the other alike resistor, I was doing it from memory which isn't that good. Of course your schematic is correct esp. if verified on the printed circuit board which is labeled on both sides.

You are getting technical on me where the resistor should be within 5% tolerance checked with at least one leg free and yes heat could be the culprit as it changes the value over time or directly when under load. That is the extent of my troubleshooting knowledge, any other technical questions and stpeteshepher on eBay should be contacted or any other reliable source.

I don't even bother to check the resistors, I just change them out as a matter of habit whether they look fried or not. Eventually they will begin causing trouble in the long run.

It's worth a shot to change the resistors out and at least elimanates the two as a problem even if the sub still refuses to work. From there it would be more troubleshooting looking for hot spots (browning) on front and back of the board not counting areas that just run hot and might slightly discolor an area of the board and more testing. Some components you can't easily check and just have to swap them out with new ones but I hope it doesn't come to that because sometimes it's easier to buy a used working sub and cheaper time wise unless you just want to give it a go.

It's hard to mess up the repair, even missing the trace hole with the tip and searing the green coating (I forget the name of it) doesn't hurt anything. Over heating a trace where it might lift off or separating it from the board when you might snag it when pushing a wire leg through and it will still probably work when soldered. Most of the time the biggest pain is scracthing and picking away any over sprayed foam.that might be on them.

I'm not pretending I know what I'm doing but have done it basically on advice and advice only because I inquire before I venture in. Even a Klipsch parts guy (phone call) told me that changing those resistors would probably bring my first sub back to life and it did. (Must have caught a Klipsch tech on a good day)

For what they are the 2.1s sound pretty good are usually worth trying a repair.

[DEC]

This is an Excellent Thread, Keep it going guys! Other people will certainly be looking for this information in the future. This is one of the better Klipsch Forum Threads I have seen.

DEC, Let me know how things work out for you. I am crossing my fingers for you.

Thanks Mr. Clean ... I've got my fingers crossed as well.

[DEC]

Sorry about mis-stating the number for the location of the other alike resistor, I was doing it from memory which isn't that good. Of course your schematic is correct esp. if verified on the printed circuit board which is labeled on both sides.

You are getting technical on me where the resistor should be within 5% tolerance checked with at least one leg free and yes heat could be the culprit as it changes the value over time or directly when under load. That is the extent of my troubleshooting knowledge, any other technical questions and stpeteshepher on eBay should be contacted or any other reliable source.

I don't even bother to check the resistors, I just change them out as a matter of habit whether they look fried or not. Eventually they will begin causing trouble in the long run.

It's worth a shot to change the resistors out and at least elimanates the two as a problem even if the sub still refuses to work. From there it would be more troubleshooting looking for hot spots (browning) on front and back of the board not counting areas that just run hot and might slightly discolor an area of the board and more testing. Some components you can't easily check and just have to swap them out with new ones but I hope it doesn't come to that because sometimes it's easier to buy a used working sub and cheaper time wise unless you just want to give it a go.

It's hard to mess up the repair, even missing the trace hole with the tip and searing the green coating (I forget the name of it) doesn't hurt anything. Over heating a trace where it might lift off or separating it from the board when you might snag it when pushing a wire leg through and it will still probably work when soldered. Most of the time the biggest pain is scracthing and picking away any over sprayed foam.that might be on them.

I'm not pretending I know what I'm doing but have done it basically on advice and advice only because I inquire before I venture in. Even a Klipsch parts guy (phone call) told me that changing those resistors would probably bring my first sub back to life and it did. (Must have caught a Klipsch tech on a good day)

For what they are the 2.1s sound pretty good are usually worth trying a repair.

No problem on the resistor identification, I just really wanted to make sure I was on the right track before desoldering/removing the wrong component.

And I agree, even if my R120 resistor isn't the sole basis of my sub volume problems, at least replacing it (and R107) eliminates any current/future issues coming from those 1/4-watt resistors. I am of course hoping that doing this work will bring my sub back to life, but we'll see. I am also not pretending to know what I am doing either, but with your help (as well as Mr. Clean and others), I hope to do the right thing and at least not screw anything up more than it already is.

Thanks again for all of the help and good information. I'll let you know how it goes.

Don

[DEC]

Well, I unfortunately have bad news to report.

After I
desoldered and removed resistor R120 (which previously looked like it
was damaged), it turned out that a small amount of the over-sprayed
brown foam stuff that is slopped around in quite a few places on the
various internal boards in the sub was on the end of the resistor in
question, which made it look like it was damaged when it actually
wasn't. Anyway, I went ahead and replaced the two 1/4-watt 82-ohm
resistors R120 & R107 with 1-watt 82-ohm versions and nothing
changed (and the job went well and I didn't need to take the power supply circuit board out
to do the work). I unfortunately still get no sound from the subwoofer unless I
crank the
sub volume level control potentiometer to maximum, and then I just get
the same anemic low-level volume even with a heavy bass passage, so
there is obviously something still wrong with one or more components on
one of the circuit boards inside the sub unit. The trouble is, nothing
else looks burned, discolored, or obviously damaged, so I guess it
could be anything at this point.

I am going to have to think
about what's next. I would definitely like to get my 2.1 sub working
again, but I also don't want to spend an arm and a leg doing it. I am
also not willing to start buying replacement circuit boards from
Klipsch, as with my luck, whatever I started with wouldn't be the right
board and then I would just be out more money with no real benefit. I have been in touch with stpeteshepherd from eBay (aka Klipsch forum member
"stpete cooling"), and I may have him take a look at it, although he typically focuses
more on ProMedia 5.1 systems as compared to 2.1 systems.

Don

[razzz42]

To bad that didn't work. I'd try checking the DIN plug next that plugs into the panel from the controller by turning the unit on and playing some music through it and then flexing the plug at the vinly/rubber boot at the plug to see if you can get the sub to respond as the plugs have a history of failing. If no go then troublleshooting further is your only option or buying a used working sub as getting it repaired might cost more than it's worth.

[DEC]

In terms of the original Klipsch DIN plug, that already failed back in 2008, at which point I had Mr. Clean replace it with one of his beefed-up DIN plugs and everything ran fine for the better part of two years after that. When I subsequently encountered the issue with little or no sound coming out of my sub last month, I sent the control pod back to Mr. Clean thinking that something had gone south with it. However, he checked it and gave it a clean bill of health. Despite that, I went ahead last night (after the replacement resistors failed to bring my sub back to life), and plugged my control pod equipped right satellite speaker from my second set of ProMedia 2.1's into the bad sub (which, by the way still has a functional Klipsch DIN plug), and the sub was still essentially dead with regard to any significant sound output. So, the problem is definitely not with the DIN plug or control pod. (And I also wiggled both DIN plugs a bit in the jack on the back of the dead sub to see if I could get any response, but absolutely nothing happened in terms of intermittent sounds, etc.).

Since I am not much of an electronics guy, I am not sure how much more trouble-shooting I can viably do. I suppose I could start removing the full array of circuit boards one-by-one and testing resistors for stated resistance from the schematics, but if that's not the underlying problem, I am not sure what to do exactly for all of the other components in terms of acceptable versus non-acceptable readings (e.g., transistors, capacitors, diodes, etc.).

And while I haven't done any searches for used 2.1 subs, I don't have a feel for availability of these, and I guess I am a bit hesitant about the "working" part as I might be inheriting someone else's dead or dying sub. Beyond that, I realize I could get a new 2.1 system, but that's not in our budget from a fixed income perspective. So, with all of that said, I may or may not go the route of having stpeteshepherd take a look at it, however, that would need to be done with some total cost ceiling in mind ... especially considering the back and forth shipping costs with the heavy transformer-equipped innards of the 2.1 sub. (And so far, between recently rechecking the DIN plug with Mr. Clean, along with ordering fuses, resistors, soldering supplies, and what not, I am already $50+ into the repair effort with little to show for it).

Anyway, one final option would be to run the compromized system as a 2.0 system. The satellite speakers work and sound good, and as far as 2.0 systems go, the Klipsch satellite speaker sound output and quality is still very good even without the sub. And since this is for my wife's iMac and she is more than happy with the improved sound quality over the built-in internal speakers (which aren't too shabby in their own right IMO), that may also be the route we might end up going in. BUT, it still personally bothers me to not have the full capability of the system, especially after having invested the time (and some cost) involved with my efforts to date. I'll probably go ahead and recontact stpeteshepherd on all of this, but even he wondered about the cost effectiveness of further trouble-shooting if the resistor swap-out didn't end up working.

Don

[Mister_Clean]

Damn Man, i was really hoping that would have worked. I have had a few people with the same problem in the past but nobody has ever wrote back to help the rest of us figure out how to fix it ourselves.

[DEC]

Yeah, I was really hoping this would work too. However, on the bright side, I am aware of at least 2 or 3 people who had the same problem, replaced one or both of the resistors in question, and got their 2.1 subs up and working again. So, if you are lucky in that the resistor(s) are the singular issue, doing this work is potentially worthwhile and cost effective. And as others have stated, replacing/upgrading the two resistors is probably a good preventive thing to do even if you're not having problems.

[dzfan]

Full schematics available here:

http://www.thompdale.com/bash_amplifier/2-1/2-1_bash_amp.htm

I have the same fried resistor (R107), and the same problem as the original poster, with backwards volume and very quiet sound. Just ordered (2) 82-ohm 1/2-watt resistors from Digikey. I'll post again when I receive and install them.

@DEC: did you check the sub-woofer board for damaged components?

[DEC]

dzfan,

I already posted the link as well as the entire set of schematics for the 2.1 in my earlier thread ... "Full Set of Schematic Diagrams for ProMedia 2.1 System": http://forums.klipsch.com/forums/t/137146.aspx

And yes, as I already reported on page 1 of this thread, after replacing the two original 1/4-watt 82-ohm
resistors R120 & R107 with 1-watt 82-ohm versions (and not getting good results), I carefully checked all of the boards in the subwoofer and nothing
else looks burned, discolored, or obviously damaged.

Don

[dzfan]

Couldn't wait for the 82 Ohm resistors to arrive so I scrounged up a 100 Ohm and a 470 Ohm and wired them in parallel. Turns out to be just right with a theoretical resistance of 82.5 Ohms. I installed them in the spot for R107 without difficulty and I still observe the same symptoms. Looks like the resistors I ordered won't be helping. I could still try replacing R120, although it doesn't look burned.

DEC, I figured you might have seen the rest of the schematics if you had seen the Power Board. Sorry bout that. I hadn't seen your other thread. Looks like we're in the same boat now. I'm going to continue testing the rest of the components with a multimeter to see if they match the specs on the schematic, particularly the transistors and caps. I'll let you know if I find anything suspicious.