UVICS - Univibe In a Crybaby Shell

[R.G.]

Great! Having the opposite log taper from what's needed does dramatic squeezing of the pot range.

You mention lowering LFO caps to 4.7uF. Were they 10uF or 1uF?

[Brymus]

They were 10uf before.

[R.G.]

And these are the three stacked ones connecting to the speed pot, right?

Those were 1uF in the original. Going to 4.7 or 10uF makes the LFO ...gooo......veeerrrryyy........sssslllooooooowwwwww...

I had to go check the schemo and parts list to see if my normal great  typing accidentally made the values 10uF. But the parts list is correct at 1uF.

[Brymus]

Nope
I lowered C22 and C23 
So that had nothing to do with my LFO speed?
It was all the taper and limiting resistors ?

[Brymus]

I was thinking about doing the indicator mod with an LED in series with R 46 to ground,then using the 3PDT to short out the LED in bypass mode.
Do you think that will work OK ?

[R.G.]

I lowered C22 and C23 
So that had nothing to do with my LFO speed?
It was all the taper and limiting resistors ?

I think it was all the reversal of the pot connections and messing with tapering and limiting resistors.

C22 and C23 have nothing to do with the timing of the LFO, except perhaps loading the LFO output might affect its speed a little, but it's very much a secondary, tiny effect. What they do is to block DC from getting to the hot side of the depth pot (c22) and into the bulb driver (C23). If they're not big enough, they filter out (i.e. make smaller) the lower frequencies going into the bulb driver.

I was thinking about doing the indicator mod with an LED in series with R 46 to ground,then using the 3PDT to short out the LED in bypass mode.
Do you think that will work OK ?

I personally wouldn't do it that way. I've been messing with a couple of ways to use an indicator. The simplest way is to put it in series with the lamp. It'll be way bright in most cases. Parallel it with a resistor to dim it some.

[Brymus]

I lowered C22 and C23 
So that had nothing to do with my LFO speed?
It was all the taper and limiting resistors ?

I think it was all the reversal of the pot connections and messing with tapering and limiting resistors.

C22 and C23 have nothing to do with the timing of the LFO, except perhaps loading the LFO output might affect its speed a little, but it's very much a secondary, tiny effect. What they do is to block DC from getting to the hot side of the depth pot (c22) and into the bulb driver (C23). If they're not big enough, they filter out (i.e. make smaller) the lower frequencies going into the bulb driver.

Ahh OK gotcha,that actually makes sense,because I thought I noticed Freq response had changed a little.
I was attributing that to raising R1 to such a high value.

I was thinking about doing the indicator mod with an LED in series with R 46 to ground,then using the 3PDT to short out the LED in bypass mode.
Do you think that will work OK ?

I personally wouldn't do it that way. I've been messing with a couple of ways to use an indicator. The simplest way is to put it in series with the lamp. It'll be way bright in most cases. Parallel it with a resistor to dim it some.

OK thanks again,the one I am going to use is an ultra bright blue LED.
Even with a 4k7 at 9V its almost blindingly bright.
Flashing under the treadel it should look really cool.

I have yet three more questions RG.
And I really apprecait all the help.
How would you rid the farty distortion on the bar chords ?

150K input resistor seems awfully drastic,and it still distorts slightly at full strum.
Is this a problem in the originals ?

And finally do you think a higher supply voltage would give better results ?
The lowest rated cap I have on the board is 35V.

[Brymus]

OK it works 
How do I increase the max speed?

If you're OK with increasing the min speed too, cut the 1uF caps in the LFO by half; that will increase both min and max. Changing Q11/Q12 to an integrated darlington or changing Q11 to a J201 and changing R40 to a higher value will give you a lower minimum speed before the LFO quits because of loading on the capacitor chain, so changing Q11/Q12/R40 and cutting the value of the capacitor chain will give you a higher max speed with the same min speed.

Duh you said right here cut the 1uf caps
I was searching for the info on the driver darlington,which I am going to try,but it took awhile to find the info I knew was here.
So it sounds like adding the FET and higher value resistor along with going to .47uf caps is the way to go.

[Brymus]

I went to the Dunlop site and listened to the demo vids for the "Rotovibe" and "Univibe"
Now I know these are supposed to sound different.
They have quite a bit more speed,and depth.

SO I was tracing out the circuit trying to find a way to add depth,and I think I found an error.
The depth pot is supposed to have one lug grounded and so is R 50,neither hit ground as far as I can see by tracing the layout and PNP.
And my meter has no continuity at the end of R 50 thats supposed to hit ground.
The trace runs down and hits a pad for a jumper for the cancel function (I thought) and ends there.

Connecting that pad to ground gives the proper depth and phase.

[RedHouse]

I went to the Dunlop site and listened to the demo vids for the "Rotovibe" and "Univibe"
Now I know these are supposed to sound different.

Careful with that comparison Brymus, the Dunlop UV-1 (Uni-Vibe) isn't exactly a good example of what they should sound like, and Dunlop's Rotovibe is not even close, it's actually a cousin to the MXR Phase-100, different caps and LED/LDR operation which isn't the univibe tone at all. The Dunlop "Stereo Univibe" isn't even a univibe at all, it's a chorus pedal like a CE-2 or other modulated delay pedal.

Try Google'ing for sound clips of Bob Sweet's mojovibe, or the K&R,heck even the deja-vibe is better than the UV-1. I've lost my sound clips in my big computer hard drive faux-pas (crashed, no recovery) or I'd post them for you here. The throb/lope is unique in a vibe and why it remains popular even though it's older than dirt and uses the primitive bulb/ldr technology, no fancy FETs or VCAs.

[R.G.]

SO I was tracing out the circuit trying to find a way to add depth,and I think I found an error.
The depth pot is supposed to have one lug grounded and so is R 50,neither hit ground as far as I can see by tracing the layout and PNP.
And my meter has no continuity at the end of R 50 thats supposed to hit ground.
The trace runs down and hits a pad for a jumper for the cancel function (I thought) and ends there.
Connecting that pad to ground gives the proper depth and phase.

Hmmm. The trace that runs from the depth pot cold lug to R50 continues up into the board and ends at a position where there should be a jumper wire between D1 and C19. That connects the trace to ground. I notice that in my typical boneheaded fashion I did not put that jumper wire onto the parts location.   

If you didn't guess it should be there, that would account for it.

[RedHouse]

(in the voice of Maxwell Smart)...

"The 'ol missing jumper on the board trick!"    

[R.G.]

Jumper location is now shown on the parts location diagram at geofex.

[Brymus]

SO I was tracing out the circuit trying to find a way to add depth,and I think I found an error.
The depth pot is supposed to have one lug grounded and so is R 50,neither hit ground as far as I can see by tracing the layout and PNP.
And my meter has no continuity at the end of R 50 thats supposed to hit ground.
The trace runs down and hits a pad for a jumper for the cancel function (I thought) and ends there.
Connecting that pad to ground gives the proper depth and phase.

If you didn't guess it should be there, that would account for it.

Well I knew it was for a jumper.
But since it was omitted and ran to the pads for the cancel function,I thought you left it out on purpose.  

I used a ground pad in the header,just connected pads X and N with a jumper.
But now you can hear the LFO thump at loud volumes.
I will switch it if I can get that jumper under the 1000uf cap glued to the board.

I also jumpered the 100R input resistor.
This raised the pre amp to 14.69 V with 18V at the filter caps.

And I switched C22 and C23 back to 10uf.
Lowered R1 back to 22K.
That really improved the tone.

The distortion is the same,only on full strum bar chords.
Which after playing it an hour or so last night doesnt seem to be a huge issue in real use.
Its jusy annoying when it farts unexpectedly.

I also made R42 and R43 600R this helped the max speed.
But I am going to try halving the LFO caps to .47uf and raising R42 and R43 back up and see how I like that.

[Brymus]

Yeah I havent messed with it ,to busy playing it 
It does "Bridge of Sighs" freakin dead on perfect with a little treadle work. 

I think after RG posts those daughter boards he was talking about it.
I'll add the indicator and it will be done.

[R.G.]

Yeah I havent messed with it ,to busy playing it 
It does "Bridge of Sighs" freakin dead on perfect with a little treadle work. 

Sweet~!

I think after RG posts those daughter boards he was talking about it.
I'll add the indicator and it will be done.

I've actually just been leaving the old version up there until you got yours good and working. I wanted to be sure you didn't get to a place where the info you needed wasn't there. So if you're satisfied, I'll put up the version with all the collected bits and bobs and the daughter boards.

[Brymus]

I've actually just been leaving the old version up there until you got yours good and working. I wanted to be sure you didn't get to a place where the info you needed wasn't there. So if you're satisfied, I'll put up the version with all the collected bits and bobs and the daughter boards.

Satisfied is kinda strong.
More like content for the time being 
The more I learn about it and play it,the more "ideas" I get about how to mod it.

Also:

The occasional "farty sound" is still a concern.
And now that the depth pot is grounded the bulb gets dimmer at the min and max speeds,brighter in the middle of the treadel sweep.
And turning it down dims the bulb while slowing/canceling the LFO.
In fact the depth pot will turn the LFO off then the bulb will go dark at the very min.
IDK if this is normal or not?

Go ahead and post the newest version If you would.
I'd like to get the indicator working.

[RedHouse]

The occasional "farty sound" is still a concern.

Do yourself a favor, now that you did the diode stack thing to your 7812 and you can put to rest the notion the voltage being the issue of the blocking distortion, change R1 up from it's stock 22k value as I posted earlier.  Start about 27k and sub-in higher resistors until the distortion goes away, again, I've used anywhere from 27k all the way up to 75k in past tweak sessions, just try it, you'll see.   

[Brymus]

The occasional "farty sound" is still a concern.

Do yourself a favor, now that you did the diode stack thing to your 7812 and you can put to rest the notion the voltage being the issue of the blocking distortion, change R1 up from it's stock 22k value as I posted earlier.  Start about 27k and sub-in higher resistors until the distortion goes away, again, I've used anywhere from 27k all the way up to 75k in past tweak sessions, just try it, you'll see.   

You might have missed it.
But I have R1 socketed and used values up to 150K
It stayed the same.

But it might interest you to know that when the depth pot wasn't grounded.
And the pre amp was running at 12V raising R1 did dramatically reduce the fartyness.

But now that those two problems have been sorted it sounds better with R1 at 22K since a 150K stills lets the occaisional fart through.(same as 22K)
Only with my PAF's not my single coils.

I did some reading and the dimming effect with the depth pot is normal.
IDK if it should also slow the LFO though.

After listening to clips at JC's page his have more depth or phase.
Maybe it the Resly tone caps I am hearing and not the stock ones ?

[Brymus]

Something else.
UVICS part # R 49 and R 50 are 47K
In the other Vibe schematics these are 4k7.
Is 47K correct or a typo ?