UVICS - Univibe In a Crybaby Shell

[Brejna]

Is there any reward   
Thanks for fast responce, I attend to build it next month so this was only area that I couldn't understand.
Is there any specific opto or?

Reward? It depends.    First you have to want to have an blinking LED. Then you have to pick that one of the three different ways to do it.

There is an opto I was planning to use, but there are many, many optos with the same pinout. They differ primarily in their speed - which does not matter in this case at all - and in their current transfer ratio (CTR). The CTR is the ratio of current in the phototransistor to current in the LED. For this application, you want it to always be greater than 100% - that is, the current through the LED being driven makes more than amount of current flow in the photo transistor. I'd be tempted to use a photodarlington with big CTR; but then the LED would merely blink on and off, no fading.

I attend to make it with the led blinkin option, and if you guide with optotransistor I am willing to try all 3 option

[Brejna]

I have 2 more quetions:
- can i use 2n5088 for q16?
- do i need to ground R12?
Brane

[R.G.]

Sorry - it's been busy here.

I would pick an optoisolator like one of these:
Vishay  VO617A-3
CEL PS2501
Everlight EL817
selecting the options for the highest current transfer ratio you can reasonably get.

You can *try* a 2N5088 for Q16. It may be fine. I specified a darlington to minimize the load on the driving side.

I'm a bit confused about the question on R12. One side of R12 is grounded on the PCB traces.

[Brejna]

Thanks for The input 
I have notice that trace that goes from R12 is left opened on The son of uvics board. From the schematic it should be grounded or?

[R.G.]

Can you point to the link you used to see that detail?

I checked my original design files and didn't find an open.

[Brejna]

I have download pdf from www.geofex.com

[R.G.]

OK, I found the problem. Apparently there was a bug in printing the PDF for the toner transfer. It's missing the highlighted trace. Solder a wire on there.

[Brejna]

Thanks, and sorry for bothering this much 

[tubegeek]

Rookie mistake.

[R.G.]

I know, I know. I'm a perpetual beginner.   

[Brejna]

...and last one that i forgot to ask is value of R53,54 and 55? 

[Brymus]

You know the prototype I built still works and sounds great 
thanks for that RG,it brought me a lot of great fun playing Pink Floyd with it of course "Bridge of Sighs" is mandatory with this pedal
I think I might have to build it with the newest version and compare,wish there was a cheap way to get usable wah shells...

[Brejna]

What is the best way to check vactrol? Audio part of pedal works, but LFO doesn't. it was working normally and then stopped. I've changed all LFO transistors and still nothing.. So is it vactrol?

[R.G.]

What is the best way to check vactrol? Audio part of pedal works, but LFO doesn't. it was working normally and then stopped. I've changed all LFO transistors and still nothing.. So is it vactrol?

Swapping transistors is not a very good debugging technique.

The best way to check the vactrol is to hook up your ohmmeter across the resistor side and a 9V battery and variable resistance across the LED side and vary the current through the LED. If the ohmmeter reading changes, the vactrol is good. If it doesn't you have to first reassure yourself that you're actually varying the current through the LED, then decide if the Vactrol is dead or your test procedure is flawed.

If you use a pot for a variable resistor in the LED - test, be sure to put an approximately 1K fixed resistor in series with the pot and LED so you can't accidentally turn the pot to zero resistance and thereby cook the LED to death.

If this is not immediately satisfying, falling back on the techniques in "what to do when it doesn't work" would be very helpful.

[Brejna]

What is the best way to check vactrol? Audio part of pedal works, but LFO doesn't. it was working normally and then stopped. I've changed all LFO transistors and still nothing.. So is it vactrol?

Swapping transistors is not a very good debugging technique.

The best way to check the vactrol is to hook up your ohmmeter across the resistor side and a 9V battery and variable resistance across the LED side and vary the current through the LED. If the ohmmeter reading changes, the vactrol is good. If it doesn't you have to first reassure yourself that you're actually varying the current through the LED, then decide if the Vactrol is dead or your test procedure is flawed.

If you use a pot for a variable resistor in the LED - test, be sure to put an approximately 1K fixed resistor in series with the pot and LED so you can't accidentally turn the pot to zero resistance and thereby cook the LED to death.

If this is not immediately satisfying, falling back on the techniques in "what to do when it doesn't work" would be very helpful.

Thanks, I've checked it and it works. In dark it goes to 20M+ and in the light 200-300R

[R.G.]

If by "in dark" and "in light" you mean "the LED full off" and "the LED full on at some current" then it's fine.

If you mean actually in light and dark, you don't have a vactrol, which is an integrated light-tight package.

The LFO in the univibe will stop if the resistance of the speed pot is too high. The original prototype of this speed control I made had problems with stopping if I ran the LED current to fully off.

[Brejna]

If by "in dark" and "in light" you mean "the LED full off" and "the LED full on at some current" then it's fine.

If you mean actually in light and dark, you don't have a vactrol, which is an integrated light-tight package.

The LFO in the univibe will stop if the resistance of the speed pot is too high. The original prototype of this speed control I made had problems with stopping if I ran the LED current to fully off.

Yeah you are right, I meant LED full on/off. When I first build uvics (when it was working) only issue was with blocking LFO like you said, but I put 4k7 resistor in positions of R52 and it was fine.
Since I've ruined few solder pads with disoldering I will make another board and start again with this.

[Brejna]

I have etched new pcb and solder it and it works, I tried LED method 2 with transistor, for R55 I have put 22R and for R54 47K. When I engage it, LFO stops and when I disengage it works.. Is it value of resistors that I am using or something else?

[R.G.]

I have etched new pcb and solder it and it works, I tried LED method 2 with transistor, for R55 I have put 22R and for R54 47K. When I engage it, LFO stops and when I disengage it works.. Is it value of resistors that I am using or something else?

Let me be sure I understand. The LFO works when the pedal is NOT engaged, presumably by the flashing light being visible, but the light stops flashing when the pedal IS engaged? Is that right?

[Brejna]

Sorry for this it was my bad, I had shorted trace.
It works, only thing that could be improved is LED tracking..
EDIT: Slower settings of LED do not work at all, then when I raise speed LED glows again. I have lower R54 to 24K and there is not to much improvment.. BTW is there a way to separate LED from Intensity?