SOLVED ElectroVibe Mini - no effect/bulb not flashing

[KindCanuck]

After writing I'm going to clean more flux, but here's where I'm at right now:

The bulb doesn't flash, so I assume it's the LFO not passing signal. Both Depth and Rate don't function. I can produce modulation by closing/opening the case, so the LDR's and rest of the circuit works. There's a tone change when swapping to Chorus, but still no modulation. Gain and Bias change the bulb intensity. 1uF caps are a mix of Tantalum and MLCC because I couldn't source ones short enough, they were out of stock at mouser. Could that have bearing on this?

I have no idea where to start. The good thing is that audio is great throughout, I just need that damn bulb to do its thing. Help?!

 

[Diynot]

I would start by verifying all the component values in the lfo section which appears to be everything on the right of the lower board and a few components near that right header on the upper board. You can reference the full Electrovibe schematic to get an idea of what constitutes the LFO section. I would say lose the sockets, but you’re pretty well committed at this point. Make sure the 5088s are getting the correct voltage. The tants should be fine, just make sure they are oriented correctly.are you getting firm connection with your “headers”? I don’t think I have ever seen sockets used as a header, I would think that would cause clearance issues

 

[KindCanuck]

I'm using these component numbers though the actual layout is slightly different on my board as you can see in the original pics. What are correct voltages for the 5088s? These are the readings of the bottom board's 5088's:

Q1
1 - range from 4.5ish to 8.5ish
2 - I'm getting anomalous readings... maybe 7 or maybe 16v
3 - 16v

Q2
1 - anomalous like pin 2 above (connected in a darlington arrangement I believe)
2 - same 4.5 to 8.5
3 - 16v

Q3
1 - 6.45v
2 - 7.14v
3 - 11.85v

Q4
1 - 7.12v
2 - 7.6v
3 - 11.84v

What should I be seeing?

 

[KindCanuck]

I'm dying here. I successfully built an Abyss that's filling the vibe void, but I'd really like to get this going. Any ideas? Bueller?

 

[neiltheseal]

I have had a similar problem with my Univibe that I built (largely stolen from the electrovibe).

Turns out I used 47uf caps in the lfo section instead of 1uf.

Are you absolutely sure your lfo caps are the right value? If the value is too high it won’t pulse.

 

[Mcknib]

To narrow down your problem area (using the schematic) and to figure out if it's in the LFO or lamp driver section first check you get alternating voltages on the speed pot lug 2s as you turn it, make sure your trimmers are the correct value bias 250K (code labelling 254) and gain 500R (code 501)

If you get fluctuating voltages up to that point you know the LFO output is fine if not I'd check the voltage points you can see labelled on the schematic

Some you've already checked Q1 and 2 collectors which are correct I think (label your transistors C,B,E rather that 1,2,3 to make it easier to check) you'd get around 16v with the voltage drop through the diodes D4 and 5

Check you get around 8v ish at the junction of R8 and 11 etc

If all's good move onto to your lamp driver section starting at the LFO input

RGs article gives you a fair idea of how it works

< The Technology of the Univibe

 

[KindCanuck]

I have had a similar problem with my Univibe that I built (largely stolen from the electrovibe).

Turns out I used 47uf caps in the lfo section instead of 1uf.

Are you absolutely sure your lfo caps are the right value? If the value is too high it won’t pulse.

Thanks for the reply, all values appear correct

To narrow down your problem area (using the schematic) and to figure out if it's in the LFO or lamp driver section first check you get alternating voltages on the speed pot lug 2s as you turn it, make sure your trimmers are the correct value bias 250K (code labelling 254) and gain 500R (code 501)

If you get fluctuating voltages up to that point you know the LFO output is fine if not I'd check the voltage points you can see labelled on the schematic

Some you've already checked Q1 and 2 collectors which are correct I think (label your transistors C,B,E rather that 1,2,3 to make it easier to check) you'd get around 16v with the voltage drop through the diodes D4 and 5

Check you get around 8v ish at the junction of R8 and 11 etc

If all's good move onto to your lamp driver section starting at the LFO input

RGs article gives you a fair idea of how it works

< The Technology of the Univibe

This is fantastic! I was looking for an article like this, but google was feeding me forum posts with less than technical replies. I appreciate the work you put in to the reply. I'll get back to you after I've done some more investigating. THANK YOU!

 

[Robert]

Just in case you aren't aware, you can power the lower LFO PCB without the upper analog board attached.

That might make troubleshooting a little easier.

 

[Mcknib]

Meant to say that all your component values and orientation that I can see look correct I can't see R29 the 47R or most of the cap values and orientation

 

[KindCanuck]

I verified all the components, all are correct. I may pull the other 1uf ceramic caps to put some electrolytics now that I have some, space permitting.

I verified the voltage at both middle pins of the speed pot is varying as I adjust, though it is a static voltage.

Where should I measure to see the actual “blooming” voltage from the lfo?

I have about 7v at the junction of R8 and R11.

Pin 1 of the gain pot is not connected, should it be tied to pin 2? Thats the only thing I could see might be questionable. Everything else looks good, complete circuits… I’m baffled.

 

[KindCanuck]

I FUCKING GOT IT. One (or maybe both) of the 10uf Tantalum caps was toast and not passing the LFO to the lamp circuit. It's happily pulsing next to me as I write this. I'll box it up and post pics tomorrow

Thank you to all @Mcknib @neiltheseal @Diynot @Robert for the tips, it really helped. thank you so much!

 

[Diynot]

Good deal and rock out with your new tone machine! Mark this thread as SOLVED!

 

[Mcknib]

Glad you've got it fixed

Tants go fairly easily either with a dramatic explosion or they fizzle out especially if they're in backwards you should pop a couple just for fun

I know I would