# 'Nuther Photonvibe question



## geekmacdaddy (Feb 12, 2019)

I remember having to be careful when dialing in the bulb on other univibe builds...can you suggest a starting position on the trimpot (is it trimpot 3)? 

Thank you 
Geek


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## geekmacdaddy (Feb 14, 2019)

And what do the other trimmers do?

thanks


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## Robert (Feb 14, 2019)

From left to right, the trimmers are:

Blend - Adjusts the blend of clean / vibe signal
Gain - Adjusts the intensity of the lamp
Offset - Adjusts the DC bias (mid point) of the sweep

I would start with the Gain and Offset near the middle and adjust from there.   Just watch the brightness of the lamp, I've never really considered the fact that you could blow the bulb, but I suppose it's possible (12V bulb running on a potential 18V source).


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## geekmacdaddy (Feb 14, 2019)

Robert said:


> From left to right, the trimmers are:
> 
> Blend - Adjusts the blend of clean / vibe signal
> Gain - Adjusts the intensity of the lamp
> ...


Thank you, Sir ✍


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## geekmacdaddy (Feb 16, 2019)

One problem with the builds. the both pop when engaged and disengaged. suggestions?

Thanks


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## Prefectingfjords (Mar 18, 2020)

geekmacdaddy said:


> One problem with the builds. the both pop when engaged and disengaged. suggestions?
> 
> Thanks



Did you ever figure this out?  I’m going to try to build one of these soon.


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## Barry (Mar 18, 2020)

Robert said:


> From left to right, the trimmers are:
> 
> Blend - Adjusts the blend of clean / vibe signal
> Gain - Adjusts the intensity of the lamp
> ...


Seems like they would have put a 12 volt Zener in there to prevent that


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## Chuck D. Bones (Mar 19, 2020)

You should be ok.  The bulb is rated for 12V @ 40mA.  The 18V isn't really 18V, probably more like 17V.  With TR2 fully CCW and TR3 fully CW, the most DC voltage the bulb could see is around 12.5V.  The thing that kills incandescent bulbs is the large current surge when you first turn them on.  Q3 acts as a current limiter and keeps the peak current down to a very safe level.


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## Robert (Mar 19, 2020)

A builder stress tested this circuit by running the LFO wide open for two days straight on the bench.      

The lamp did not fail, so I suspect you'll be fine while dialing it in.


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## Chuck D. Bones (Mar 19, 2020)

Q3 could benefit from a heatsink.


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