SOLVED Lab Rat Gated on LED Setting

joelorigo

joelorigo

Well-known member
My Lab Rat is sounding gated as a note fades or is gently plucked on the LED clipping selection. It does not do it on the 1N4148 selection. Picking hard it seems normal. It did not do this previously. I don't see anything jumping out at me looking at the guts. Anyone have any suggestions on what the issue is?
 

Attachments

Last edited:
Sort by date Sort by votes
I don't think (with my half brain) that the LEDs are the issue. I think it's DC leakage.
It's essentially creating a DC offset.
Once the audio drops below the EC level, it doesn't exist to the diodes. It just looks like DC and is going to ground.
It's bit noticed on the other diodes due to the lower clipping level. The audio rarely gets that low(below Vf)

You could test this, maybe, by setting the clippers to LED, roll down the guitar volume to 20% and strum open.
Once/if the audio disappears/gates, slowly roll the volume up and see if it comes back.
Repeat the same on Si.
You *may* have to go lower on the guitar volume pot.
I hope that makes sense. I'm sh*t at tuening thoughts and instructions into understandable statements.
 
Upvote 0 Downvote
jwin615 said:
I don't think (with my half brain) that the LEDs are the issue. I think it's DC leakage.
It's essentially creating a DC offset.
Once the audio drops below the EC level, it doesn't exist to the diodes. It just looks like DC and is going to ground.
It's bit noticed on the other diodes due to the lower clipping level. The audio rarely gets that low(below Vf)

You could test this, maybe, by setting the clippers to LED, roll down the guitar volume to 20% and strum open.
Once/if the audio disappears/gates, slowly roll the volume up and see if it comes back.
Repeat the same on Si.
You *may* have to go lower on the guitar volume pot.
I hope that makes sense. I'm sh*t at tuening thoughts and instructions into understandable statements.
Click to expand...
I will give it a try!
 
Upvote 0 Downvote
joelorigo said:
Harbor Freight. On clearance sale a couple years ago. I know it's not the best but it's way better than the one I had before:) Plus I also picked up a TC1 not long after so I use that more for measuring.
Click to expand...
Maybe that’s where I got it, the sears one was before it. I also have another one for measuring Hz higher than this one can.
 
Upvote 0 Downvote
jwin615 said:
I don't think (with my half brain) that the LEDs are the issue. I think it's DC leakage.
It's essentially creating a DC offset.
Once the audio drops below the EC level, it doesn't exist to the diodes. It just looks like DC and is going to ground.
It's bit noticed on the other diodes due to the lower clipping level. The audio rarely gets that low(below Vf)

You could test this, maybe, by setting the clippers to LED, roll down the guitar volume to 20% and strum open.
Once/if the audio disappears/gates, slowly roll the volume up and see if it comes back.
Repeat the same on Si.
You *may* have to go lower on the guitar volume pot.
I hope that makes sense. I'm sh*t at tuening thoughts and instructions into understandable statements.
Click to expand...
I did the test. Yes, on the LED setting, if I have the volume rolled down and I strum a chord, when I hear the "gating" start to happen, I rolled the volume up and the sound comes back to what I would say is normal, then as it dissipates the gating starts again. It doesn't do this on the 1N4148 selection however. On that setting it behaves as one would expect.
 
Upvote 0 Downvote
Hmmm.
THis sounds odd, but get a little scrap of aluminum foil and put it over the LEDs and see if it gets better. Careful not to short anything.
Thought process, LEDs can act like small solar panels. Maybe they're picking up elextrons from the superbright led or the tube itself.
I suppose it's also possible that there is DC leaking back from the tube but I would think you would have the gating on both settings.
 
Upvote 0 Downvote
jwin615 said:
Hmmm.
THis sounds odd, but get a little scrap of aluminum foil and put it over the LEDs and see if it gets better. Careful not to short anything.
Thought process, LEDs can act like small solar panels. Maybe they're picking up elextrons from the superbright led or the tube itself.
I suppose it's also possible that there is DC leaking back from the tube but I would think you would have the gating on both settings.
Click to expand...
Ok. Use the foil to cover the LEDs? Is this to make a "shield" on them?
 
Upvote 0 Downvote
jimilee said:
Are the LEDs facing the same direction? It looks like the first one is oriented right, it’s hard to tell with the second one.
Click to expand...
Just checked them. They are in correctly, both in the same orientation. If one or both were installed wrong, it wouldn’t have worked from the beginning, right?
 
Upvote 0 Downvote
Switch has nothing to do with it.
It's either DC from the cap or tube or the LEDs picking up enough electrons to cause offset.
As crazy as it sounds, I'm inclined to think the later because it only happens with the LEDs.
Definitely try the foil, as dumb as it sounds, it's low cost and short time investment.
 
Upvote 0 Downvote
CR0SSBL4DE said:
Are both leds lighting up when working?
I would directly go for replacing the 2 leds and the spdt switch.
Click to expand...
No, I had previously noticed that when I plug it in, and when I press the footswitch to activate the pedal, the lower LED flashes on quickly, but the upper one doesn't.

I just tried it again. Upon plugging it in the lower LED flashes on quickly when the power cable makes contact with the DC jack. Then goes on and off as the plug is inserted.
Pressing the footswitch, the lower LED goes on then off. Then pressing the footswitch on and off the upper LED gives a slight glow every time. A couple of times it was brighter. I recorded this but the clips are too large to. upload.
 
Upvote 0 Downvote
I tried the tin foil thing. At first it seemed to act normally. Then after a few strums, the “gatey” thing started happening again. Maybe worse than before. I’m going to let it sit for a while and try again but that’s what I can report now.
 
Upvote 0 Downvote
joelorigo said:
I tried the tin foil thing. At first it seemed to act normally. Then after a few strums, the “gatey” thing started happening again. Maybe worse than before. I’m going to let it sit for a while and try again but that’s what I can report now.
Click to expand...
Suggestion/POV . . . . whenever I get stuck and micro-focused on one small part of circuit when troubleshooting, I will often change that micro-focus to look elsewhere for the problem. In your case, I'd start looking at the tube and the stuff going in & out of it.

But more to a more thorough troubleshooting approach, I don't see anywhere in this thread where all the supply voltages have been dbl-checked to ensure they are correct. Does the tube's heater voltage remain constant over time? Do the other voltage supplies remain constant over time?
 
Upvote 0 Downvote
You must log in or register to reply here.
Back
Top