SOLVED Electrovibe - Intensity Differences Between Speed Settings (and other issues)

[orangetones]

1) So, I have just finished up the Electrovibe. I get different intensities with each speed setting. Like if I have it on speed 1, it is less intense (can actually see the bulb change intensity) than when on speed 2 (given the same speeds). Why would the bulb driver be affected with the different speed settings?

The other issues are as follows:

2) Even with the volume maxed out, the effected signal is lower than unity.

3) When in vibrato mode, it is much louder than in chorus mode. Is this typical?

Additional info is that I get slower speeds with the speed pot 2 than speed pot 1. Differences in potentiometers? Could this be affecting the bulb driver brightness in the different settings?

 

[Robert]

Your first three observations are normal behavior for the original Univibe circuit.

1) The LFO amplitude increases as the rate is increased, this is normal.
2) There is a modification to increase the output level.
3) In Vibrato mode there is less phase cancellation so the signal will be louder

Someone else here had an issue with a difference between the two speed pots, I can't recall what they found but the most likely causes are wiring/solder connections, the footswitch itself, or (more likely) tolerance differences between the two pots themselves.

 

[Big Monk]

Your first three observations are normal behavior for the original Univibe circuit.

Someone else here had an issue with a difference between the two speed pots, I can't recall what they found but the most likely causes are wiring/solder connections, or tolerance differences between the two pots themselves.

That was me sir. Ended up being a lifted trace on the speed 1 control.

 

[orangetones]

Your first three observations are normal behavior for the original Univibe circuit.

1) The LFO amplitude increases as the rate is increased, this is normal.
2) There is a modification to increase the output level.
3) In Vibrato mode there is less phase cancellation so the signal will be louder

Someone else here had an issue with a difference between the two speed pots, I can't recall what they found but the most likely causes are wiring/solder connections, the footswitch itself, or (more likely) tolerance differences between the two pots themselves.

Thanks for the info on 2 and 3. As for 1, in not talking about different speeds (I know that the bulb driver circuit will change intensity with speed). I'm actually talking about between the 2 different speed controls. There is significantly greater swing/depth when one of the speed dials is engaged versus the other.

I'll investigate the potentiometers and connections.

 

[Robert]

There is most likely some sort of correlation between the fact that one pot gives different speeds AND intensity. I suspect when you solve one issue the other will also be corrected.

 

[orangetones]

The problem seems resolved. I measured the pots in circuit and the resistance wasn't any different. I changed that 47k resistor for a 100k on the input. And I changed out the lamp. I had originally used one from a while ago that I had from a previous univibe build. I changed it out for one I ordered specifically for this build. That bulb that was in there first might have been a spare for a 24v build that I did nearly 20 years ago...

Anyhow... Solved! Speeds are the same, intensity the same. Bulb dialed in. Hendrix played.

Sweet pedal!