Adding a rate indicator to the Vox Repeat percussion.

[breather-resistor]

Hey everyone,

I have recently built the vox/jen repeat percussion via the Analoguru schematic.

<img src="http://analogguru.an.ohost.de/193/schematics/Vox_RepeatPercussion.gif">

I am interested in adding a rate indicator.  Based on the knowledge that I have so far I expect to tap into the voltage somewhere around the unijunction transistor.  I am more concerned about implementing the rate indicator without detracting from the depth of the circuit as I know surges of voltage create the effect.

Any ideas?

Geoff

[spudulike]

Effect is by Q2 dropping signal to earth, the ujt feeds Q2 base.

Try this with a 2n3904 ...

Q2 base -->10k-->2n3904 base.
+V-->1k-->LEDa/LEDk-->2n3904 collector
Gnd-->2n3904 emitter

May need to adjust R values.

[breather-resistor]

Thanks for your info. 

Ok, I remember now, Q2 drops the signal to ground at a rate triggered by the unijunction.

I took your suggestion to make this schematic,


Is that correct?  I also tried it with the led in series to anode towards 9v cathode towards collector.

The result of the schematic above was a steady dim light through the LED with no pulsing at all.  The rest of the circuit is fully functional and I just banana clipped to the breadboard to attempt the circuit suggested.

Any ideas?

Geoff

[gigimarga]

Can you post a soundclip with it?
I am very curious how it sounds...

[breather-resistor]

Spudulike- ah yes, a second look at your post and I can see that by Led/a Led/k you meant anode and cathode.

I tried this and the result was identical, lights up, no pulse.

Gigimarga- I will indeed post a clip with it.  My interface is being goofy right now or else I would have posted it with this message.

Its definitely a a niche pedal.  It certainly needs a little help from the core schematic. 

Eagerly awaiting any ideas.

Geoff

[Br4d13y]

...............what is it?.................

[tenser75]

did anybody solved this? im curious as well to add a pulsating led thanks

[blackieNYC]

In that drawing I would expect the LED to be constantly lit. 9v->1k->LED->gnd.
Take a look at the cardinal tremolo schematic.