Electrovibe Troubleshooting: Grounding issue?

[Martycaster]

Hi there, I tried to bump an old thread earlier today but now I'll try to ask a more detailed question. So, I just finished my Electrovibe and I've double checked every solder joint so far. I have bypass signal.

The issue is, the lamp isn't pulsing. It's static. The two trimmers work just fine as brightness change when I tweak them. I triple checked all solder joints and all the trannies (I got them on sockets). I tried again and suddenly the lamp was pulsing as it's supposed to. So I closed the enclosure to give the pedal a try...but no effect came out...I reopened the enclosure and again, the lamp wasn't pulsing anymore.

I noticed that Q3 is getting a bit hot and the lamp is flickering when I move the PCB around.

Any idea what/where the issue could be? Normally when a tranny heats up it's because of too high current at the collector, right? (or am I wrong?)

Thanks for any advice!

EDIT: I got the lamp working. But there's only sound (still no effect) when the switch is on the vibrato position...when I switch to chorus it's dead quiet...still, the only two components on the PCB getting hot are Q3 and the voltage regulator (L78L12)

 

[Martycaster]

Here are a few pics (don‘t mind the solder blob on the speed switch)

 

[carlinb17]

Thank you for posting pictures, I would start out with looking at your soldering, reflowing your joints to where they are more uniform may fix the problem cold joints, and bad contact.... I know you're concerned about Q3 and attached to Q3 is Q4 the solder there looks like it could benefit from a reflow. When you move the board around and the lamp flickers is a sign of either something grounding or a cold joint. Post after images of the board once you've been able to do that.

 

[Martycaster]

Thank you for posting pictures, I would start out with looking at your soldering, reflowing your joints to where they are more uniform may fix the problem cold joints, and bad contact.... I know you're concerned about Q3 and attached to Q3 is Q4 the solder there looks like it could benefit from a reflow. When you move the board around and the lamp flickers is a sign of either something grounding or a cold joint. Post after images of the board once you've been able to do that.

Thanks a lot for the advice! I will definitely re-check all the joints. You're right...that one leg of Q4 doesn't look that good...I've also got a quite big amazon order coming my way with "soldering stuff", so I hope my workflow in that matter will improve.

I think the flickering lamp issue is fixed...there was a tangling transistor socket that I have re-soldered properly. Now it does not flicker anymore.

 

[carlinb17]

Thanks a lot for the advice! I will definitely re-check all the joints. You're right...that one leg of Q4 doesn't look that good...I've also got a quite big amazon order coming my way with "soldering stuff", so I hope my workflow in that matter will improve.

I think the flickering lamp issue is fixed...there was a tangling transistor socket that I have re-soldered properly. Now it does not flicker anymore.

does the light pulse in accordance to the spreed and intensity?

 

[Martycaster]

does the light pulse in accordance to the spreed and intensity?

Yes. Only issue is that there's no audible "vibe" effect and there's only sound when the switch is on vibrato position. No sound on the chorus side

 

[Big Monk]

LFO function without phasing points toward an issue in the signal path in the phasing section.

Also, none of the transistors, none of the components in all honesty, should be hot to the touch so focus on that Q3 section first.

 

[leeinthesprings]

I've built 3 electrovibes so far and all my Q3s get warm. All work perfectly too so I just figured that transistor gets hot for some reason. I wondered about it too...

 

[Big Monk]

Q4/Q3 are the lamp driver Darlington pair. I guess it’s not beyond the realm of possibility thus get toasty, as they are subject to brief surges of most of the current draw in the pedal as they are directly coupled to the lamp.

 

[Martycaster]

LFO function without phasing points toward an issue in the signal path in the phasing section.

Also, none of the transistors, none of the components in all honesty, should be hot to the touch so focus on that Q3 section first.

How could I test for faulty parts? For example a bad transistor.

I will also remove all the transistor sockets and solder the transistors directly on the PCB to make sure there are no bad connections.

I've been looking at the schematic trying to figure out where the issue could be...I couldn't get behind it so far but I'm not giving up yet...I don't wanna start over from scratch lol

 

[Martycaster]

I’m still troubleshooting the thing and my head is about to explode lol

I was moving around the board while strumming the guitar with the other hand and I did find out that when I put my thumb around the circled area on the pic, the “vibe effect” comes in and the pedal sounds like it’s supposed to. Also, the two positions (chorus and vibrato) are working…

Until I remove my thumb…then the vibe goes away again and the chorus side dies

What’s the issue here and how can I fix it? Is it some kind of grounding problem?

 

[Duffman]

I have this exact same problem, did you ever manage to solve this?

 

[Martycaster]

I have this exact same problem, did you ever manage to solve this?

Hi. No, I gave up. I spent too much time trouble shooting it. I ended up getting a second one. It works great and I really didn‘t do anything different than with the first one. Very strange.

 

[dcfvgb]

Did you audio probe the first board?

Check R43 , looks like a 4k7 instead of a 47k, also R12 might be a 1M instead of 2M2

 

[Duffman]

I solved the issue on mine, i think one of the legs of the photo-resistors didn't seem to connect with one of the pins of i think q9. I soldered a wire between the two points and voila it worked. I just have one other small issue now that there seems to be a tiny little bit of overdrive when the pedal is engaged. Nothing too dramatic, you barely notice it but it's not a clean signal. So i'm trying to solve that now.