Si600 Posted July 21, 2019 Share Posted July 21, 2019 I have an elderly and much loved GE-7B which I don't really want to replace as it was the third thing I bought after a bass and amp. The outward failure is that the LED doesn't illuminate when it's in use, neither on battery or power supply. Yes I'm aware of the 9v/12v LED anomaly that Boss pedals of this vintage have. The pedal works as normal otherwise. If you test the LED in isolation it's actually working so the failure is in part of the circuit that supplies said LED, or possibly tells it when to light up. Electronics is mostly witchcraft to me, so can anyone give me any pointers or tips on how to resolve it? There's nothing obviously crispy on the PCB. Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 21, 2019 Share Posted July 21, 2019 Boss pedals are switched with JFETs, so my guess is that either one of them has died, or it or an ancillary component has drifted so that the JFET is no longer biased correctly. Quote Link to comment Share on other sites More sharing options...
Si600 Posted July 21, 2019 Author Share Posted July 21, 2019 (edited) See, witchcraft! JFET is one of the little black squares in the PCB? If I find a circuit diagram on the net with the specs can I just unsolder it and replace it? Edit: looked up a circuit diagram: Q4 and Q5 in here https://www.hobby-hour.com/electronics/s/ge7b-bass-equalizer.php No, a JFET is one of the little black round things with a flat side. So I should be able to pop a pair of new ones in with careful application of a soldering iron? Edit 2: If I'm taking a soldering iron to my poor pedal anyway, are there any mod kits that are worth doing once I'm in there? Should this be in Effects rather than Repairs and Technical? Edited July 21, 2019 by Si600 Quote Link to comment Share on other sites More sharing options...
Si600 Posted July 22, 2019 Author Share Posted July 22, 2019 Naughty bump to try and get any pointers before I hack away with a soldering iron... 😉 Quote Link to comment Share on other sites More sharing options...
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