Gottastopbuyinggear Posted October 27, 2018 Share Posted October 27, 2018 I built an Fdeck HPF Pre a while ago - it's probably been on my board for more than a year, and been repositioned as I've swapped stuff around several times. Earlier this week I moved it to a smaller board, went to rehearsal, plugged in, and there's a constant hissing sound. It sounds as if the noise floor has gone through the roof, if you see what I mean...?! It's a really simple build - there's no volume or frequency pots, no phase switch - it's been built purely as a fixed 35Hz HPF so that it fits into a small enclosure. There are no loose wires or, as far as I can see, dodgy solder joints. I'm wondering whether it could be static damage to the JFETs, with static generated by separating the velcro when I've ripped it off the board. I can try replacing the transistors, or just build a completely new one (which I was thinking of doing anyway, with adjustable frequency), but if it's possibly static damage then I might rethink how I attach it to the board. Anyone have any ideas? Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted October 27, 2018 Share Posted October 27, 2018 I've had an MXR Carbon Copy die because the J-FETs in the switching circuit got fried by static (afaik). Quote Link to comment Share on other sites More sharing options...
Beer of the Bass Posted October 27, 2018 Share Posted October 27, 2018 I've also had home built FET preamps do this. I guess there must be some way to protect against it, though I'm not sure what. Quote Link to comment Share on other sites More sharing options...
Gottastopbuyinggear Posted October 27, 2018 Author Share Posted October 27, 2018 I’ll order a couple of new JFETs and see if that fixes it. If it is static the I guess keeping it grounded through an amp might help when ripping it off the board. Quote Link to comment Share on other sites More sharing options...
floFC Posted October 27, 2018 Share Posted October 27, 2018 The Velcro on the back of the pedals can create static electricity? And that can destroy pedals?? Quote Link to comment Share on other sites More sharing options...
Gottastopbuyinggear Posted October 27, 2018 Author Share Posted October 27, 2018 27 minutes ago, floFC said: The Velcro on the back of the pedals can create static electricity? And that can destroy pedals?? Difficult to tell but I’m hearing scepticism? I know what you mean. Most of us are probably moving pedals around quite frequently, so perhaps it is unlikely or it would happen more often. It occurred to me because I’d just moved it to a different board. Quote Link to comment Share on other sites More sharing options...
floFC Posted October 27, 2018 Share Posted October 27, 2018 15 minutes ago, Gottastopbuyinggear said: Difficult to tell but I’m hearing scepticism? I am genuinely surprised, I have never heard of this before. How does the static electricity build up occur? Quote Link to comment Share on other sites More sharing options...
Beer of the Bass Posted October 27, 2018 Share Posted October 27, 2018 (edited) I mean, I'm not attributing the failures I've had to velcro, but simple FET circuits do seem to be sort of sensitive. Come to think of it, I've seen FET circuits that use zener diodes as protection at the input stage. I wonder if that might be worth looking into. Edited October 27, 2018 by Beer of the Bass Quote Link to comment Share on other sites More sharing options...
Gottastopbuyinggear Posted October 27, 2018 Author Share Posted October 27, 2018 3 minutes ago, floFC said: I am genuinely surprised, I have never heard of this before. How does the static electricity build up occur? It was just a guess - static possibly being generated when the two Velcro parts are separated? The more I think about it the more it sounds a bit daft! Quote Link to comment Share on other sites More sharing options...
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