coffee_king Posted April 24, 2013 Share Posted April 24, 2013 Hey all I picked up this Boss HM-2 from a car boot for £6 the other day, but the LED doesnt light on it. Ive desoldered the LED and connected it to a 9V battery externally and it works OK. Any suggestions? Here are some images. I can post more if necessary. TA Quote Link to comment Share on other sites More sharing options...
BOD2 Posted April 24, 2013 Share Posted April 24, 2013 Could be quite hard to locate the problem but the next thing I would check is the continuity of the PCB tracks that lead to where the LED sits. You can see them clearly in that first photo - use a meter between the LED points and the solder joints at the end of each track. You might be able to trace it back further to the other end of that ribbon cable too. It could have been a bad solder join on the LED, in which case it will work if you resolder the LED back in place. Failing that it may be a problem elsewhere on the board. Quote Link to comment Share on other sites More sharing options...
icastle Posted April 24, 2013 Share Posted April 24, 2013 You don't want to be using 9v directly connected to an LED, you'll blow it. Quote Link to comment Share on other sites More sharing options...
coffee_king Posted April 24, 2013 Author Share Posted April 24, 2013 Cheers for your advise. Here is where I stand now. I checked continuity and everythign seemed ok, I connected the new LED up again and it worked. So god knows what was going on there. So that parts sorted, so thanks. OK, now new problem. Someone has obviously messed about with the before, because even with the guitar leads unplugged you can still turn the unit off and on by pressing the switch pedal. I am assuming the whole unit turns off and on because the LED lights up. Any help? Quote Link to comment Share on other sites More sharing options...
icastle Posted April 24, 2013 Share Posted April 24, 2013 That sounds like something around the input socket. It'll be a switched socket, so either there are some wires reversed or the socket is faulty. Quote Link to comment Share on other sites More sharing options...
BOD2 Posted April 25, 2013 Share Posted April 25, 2013 (edited) You possibly had a dry solder joint at the LED. By resoldering it you fixed the problem. As icastle says, the input jack usually incorporates a "switch" that makes contact when a lead is plugged in and allows the pedal to work. There are a couple of ways to do this. It might be a stereo jack socket with the "ring" and "sleeve" contacts wired so that when a mono jack plug is inserted these contacts are shorted together by the barrel of the jack to complete a circuit. Alternatively it could be a "switching" jack socket in which contacts on the socket open or close as a jack is inserted into the socket. Have a look at the input jack and see if you can make any sense of what happens when a mono jack plug is inserted. Do any bits of the socket move ? Are there 3 contacts on the jack socket (tip, ring, sleeve) ? Are two of the contacts wired together ? Edited April 25, 2013 by BOD2 Quote Link to comment Share on other sites More sharing options...
coffee_king Posted April 25, 2013 Author Share Posted April 25, 2013 hey Cheers for your help everyone, but Ive sorted the issue with the pedal being able to to switched on even without a guitar lead going into it. For some reason previously the negative from the battery was soldered onto the output instead of the input. (This was not me that did that) I found out what was incorrect by opening up one of my other Boss pedal and also I found these schematics Cheers everyone, problem resolved. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted April 25, 2013 Share Posted April 25, 2013 Hooray for BC! Quote Link to comment Share on other sites More sharing options...
icastle Posted April 25, 2013 Share Posted April 25, 2013 Excellent Quote Link to comment Share on other sites More sharing options...
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