UVICS - Univibe In a Crybaby Shell

[R.G.]

And yes the speed pot effects the lamp as it should except I have to swap the direction of its sweep.
It is a dual ganged pot both 100k ohm "A" taper. Seems that I'll have to do some tweaking though, as only a small portion of its travel is usable but I'll worry about that later.

It's got some second order problems then. Not to sweat that right now.

The light shield seem perfect in my opinion. A black rubber end cap with a shiny metallic wrapper material lined in the sides and top. Perfect size, height, and flesh to the board. Whenever I tested I had the cap on.

Good. That'll be perfect in the completed unit.

For now, turn off the unit, remove the light shield, hook a multimeter set to ohms to each LDR in turn, and use your hand, a pillow, something to darken the light to the LDRs and see if the meter says they're changing resistance. They probably are, but this is just to make sure.

Do you have access to an oscilloscope? If not, get prepped with an audio probe.

My god man you must be helping a dozen other univibe builds!

It's an occupational hazard. I released the first clone board for a Univibe before there was a world wide web, and when usenet was the only network sharing. There have been a LOT of Neovibes built over the years. I sometimes wonder about the number of clones versus the number of original univibes ever made. But yes, I get a lot of questions. As a result, there aren't many things I haven't seen happen in that circuit, so it gets easier with time. 

For instance, I have no data to support this, but your symptoms fit perfectly with an open somewhere in the phase delay path, probably the last phase/LDR section, or an open on the way to the final mix to make "Chorus". We'll go get the data and see what it really is.

[endorphin]

CORRECTION Reversed the Emitter and Collector measurement. Q13 and IC1 are still same

Ok with my audio probe I checked everywhere for some sort of phase or chorus signal but it was all clean . My power supply was putting out 18.29 volts

These measurements were taken while the bulb was flashing. The fluctuating voltages recorded were at their highest peak.

LDRs: 65-55 omhs in sunlight, 20M ohms in darkness.

Transistors 1-12, and 14 are all 2N5088
Q1
C=2.07
B=1.40
E=1.03

Q2
C=4.44
B=2.44
E=1.52

Q3
C=10.88
B=4.44
E=3.86

Q4
C=14.87
B=4.68
E=4.31

Q5
C=11.15
B=4.31
E=3.73

Q6
C=14.87
B=4.65
E=4.28

Q7
C=11.13
B=4.28
E=3.7

Q8
C=14.87
B=4.66
E=4.3

Q9
C=12.32
B=4.3
E=3.74

Q10
C=14.87
B=5.45
E=4.9

Q11
C=18.34
B=11.42
E=13.58

Q12
C=18.18
B=13.40
E=12.9

Q13: MPSW45A
C=8.56
B=8.42
E=7.17

Q14
C=14.87
B=5.8
E=5.44

IC1:78L15
Output: 14.87
Common: 0
Input: 18.47

D1
A: 13v
K: 13v

D2
A: 13v
K: 13v

D7
A:14.87v
K:18.3v

[R.G.]

Ok with my audio probe I checked everywhere for some sort of phase or chorus signal but it was all clean .

We would not expect any phase sound until after the final mixing. But it does tell us something very interesting if there is audio at
Q1 base
Q3 collector and emitter
Q4 base
Q5 collector and emitter
Q6 base
Q7 collector and emitter
Q8 base
Q9 collector and emitter
Q14 base
Q10 collector and emitter.

If you have it all those places, check for audio at the junction of R36 and R37, and this audio should have a noticeable vibrato/frequency shift every time the light changes on the LDRs.

Assuming that you reversed the labels for collector and emitter, the voltages are unremakable, and don't tell us where there is a failure.

[endorphin]

Okay Q1,3,4,5,6,7,8,9,14 there was an audio signal on all the leads you said to check but on Q10 audio on emitter but not on the collector.

Also at the junction R36 and R37 there was a clean audio signal but no "vibrato/frequency shift" no pulsing either.

As far as the 2N5088 transistors when looking at the UVICS pdf the layout from left to right with the same orientation the pinout should be Collector, Base, and Emitter right?

If so then I had the pinout wrong which changes the measurements .

[endorphin]

Does anyone know what this could mean?

[RedHouse]

Does anyone know what this could mean?

Sounds like you might need to re-check your part orientation. Mis-placed parts are the #1 cause of malfunctioning DIY builds.

[Liquitone]

hello, I have been obsessed by the sound of the uni-vibe for ages and throughout the years I've been learning how to build pedals the Uni-vibe has been the project I keep returning to, partly cause i was never able to get it right, the circuit is very interesting from the novice perspective to study and I love the linear and elegant design of the circuit.
So after reading and re-reading R.G's and Redhouse's articles and threads like these for a long while now I would like to say thank you.

I've build a uni-vibe in a crybaby shell (with a chrome vox threadle cause it looks wayyy cooler! ), but i think I've made a mistake.
I used the stereo mod from the technology of the uni-vibe article and couldn't make out if it needed a 2nd transistor in the output stage, I never looked at the UVICS layout untill yesterday  so hadn't noticed it does use that 2nd transistor.

So my output stage is as follows;
It's like the mono version with only 1 transistor but with the 68k resistor changed to 100k and added a 4k7 collector resistor. I've also changed the 22k emitter resistor to 4k7.
Then the signal goes through a 1uf cap from the emitter and a 1uf cap from the collector to 2 separate mixing stages that both get its clean signal from one 1uf cap attached to the input stage's Q3 emitter.
The in and out of phase chorus mixing resistors are all 100k and the vibrato resistors are the stock 220k with the 47k's changed to 56k

Mine hasn't got true bypass but a cancel switch at the heel.
Now when i have the pedal on cancel it sounds really full and clear, but as soon as i rock the pedal forward in chorus mode the sound thins out and the stereo image shifts in volume towards the right hand channel
(which is the out of phase signal coming from the collector) I don't really hear any thinning out in vibrato mode.
Is this because I didn't put in that 2nd transistor? or do i need to take the clean signal for the out of phase chorus mixer from an additional 1uf cap from Q3's emitter? or is it just the nature of the beast?

Q1 and Q13 are both bc 109c's, the LFO has a mpsa 13 the rest is all bc109b. The lamp is 24v, LFO runs on 24 volt and the signal path on 20 volts. the LDR are 4x 11k-500k vt90n2
I've used 0.5w metal film resistors throughout the audio circuit just to see how quiet I can make this thing. also having used lots of carbon comp in previous builds I wanted to test for myself if there's any truth to the CC mojo.
On first tests I never got the impression the pedal sounds sterile with the metal films at all. It does have a lot of high end but that can be the biasing of the lamp drivers Q emitter, the combination with the fuzz and plexi-drive, or the amps. I'll have to test it for a while during band-rehearsals to make a better judgement.

I really dig how the effect changes from mono to stereo as soon as the lamp starts flashing, very much like a leslie that starts spinning. I would definately recommend trying out the stereo mod, it sounds hauntingly beautiful and gives me the goosebumps.
It sounds much less pronounced stereo as I expected but very natural sounding so very usable without becoming a gimmick. Also, I love the sound of the lamp turning on and of gradually when going from cancel to effect on and back, I prefer it to true bypass.

So all around it seems to be working fine,. sounds like a proper uni-vibe, which I couldn't say about my previous 3 builds. so the only issues are the thinning out in chorus mode and the stereo image shifting in volume towards the out of phase chorus channel.

[Liquitone]

Ok, I solved the issue. I added the extra 1uf cap from Q3 emitter to the 100k out of phase chorus mix resistor instead of taking the clean signal from one shared 1uf cap.
There's no more thinning out in chorus mode, and the pedal sounds full and clean now .  the volume still seems to shift slightly to the right hand channel but I can live with that.

One thing I noticed is when using only the in-phase or the out-of-phase channel (slightly less) you get the typical hendrix whop-whop uni-vibe sound but in stereo it becomes more subtle, much more like a leslie. Well not what I expected but I love it.
I assume that's caused by the way the in phase and out of phase sounds meet each other in the room and create additional phase cancellations.
Anyone else  tried the stereo mod and noticed this?

next thing I'm going to is try out Vibrato on the left and clean signal on the right to see if that can create the whop-whop sound in somewhat-stereo,
by mixing the clean and moduted signal in a physical room ambeince instead of a mixer.

[Yazoo]

Are there specific LDRs recommended for this project? Tayda have Waitrony KE-10720 LDRs. From the datasheet they are 10-20K light resistant, minimum 0.5 M dark resistant. Would these be OK?

[Liquitone]

I've had very pleasing results with LDR's of those values. (i've used a matched set of 11k-500k) your's have a rise/fall time that's twice as fast as the 78ms rise/8ms fall on mine though but I don't know which are better.
The good results I had with those, where with the LFO running on 24v with a 24v lamp, single transistor lamp driver and no offset mod.
I've never had an original Uni-Vibe to measure so perhaps others with more knowledge could confirm the right light-dark values and rise/fall times.

[Yazoo]

I'm building this as a Christmas holiday project so first things first, Happy New Year to everybody.

I got a bit confused about how to wire up the power supply and the daughterboard for the "use existing wah pot" mod so I spent some time going over the schematic and layout. On the last 2 pages of the PDF on geofex.com, it shows the different wiring possibilities but shows the power as going in on pads C and D while the speed pot is wired into pads E, K and J. I think power should go into pads J and K and pads C, D and E should be wired to the speed pot. Is this correct?

[Yazoo]

Sorry, another question. I've finished my build and got it wired up. I'd be grateful for guidance on setting the trim pots. I found I could get the lamp working by fiddling with TR1 but I'm really not sure how to set the other two trimmers. Are there any recommended settings please?

[Ummagumma]

many thanks to R.G. and all of you guys.
this is my build (nevermind the not so good playing)

[RedHouse]

Looks and sounds good, I specially like that old film scratches look to the video, that's cool.

[R.G.]

many thanks to R.G. and all of you guys.
this is my build (nevermind the not so good playing)

Nice work!

[Yazoo]

I went away and looked at your "technology of the univibe" which I should have done in the first place so I understand what the trimmer on the output is for now. I've got my build working now after realising I'd wired the stomp switch wrongly. I had a dud spdt switch as well and I just need to replace that before I put everything in the shell properly.

I had a fair old time drilling the extra holes in the shell. It's a lot harder than drilling aluminium, but worth the effort!

This is a really good project.

[R.G.]

I went away and looked at your "technology of the univibe" which I should have done in the first place so I understand what the trimmer on the output is for now. I've got my build working now after realising I'd wired the stomp switch wrongly. I had a dud spdt switch as well and I just need to replace that before I put everything in the shell properly.

I had a fair old time drilling the extra holes in the shell. It's a lot harder than drilling aluminium, but worth the effort!

This is a really good project.

Thanks! And congratulations on the build.

I think the shells are actually either zinc or a zinc-aluminum alloy for easy castability and toughness, so yep, they're a bit harder to drill.

[aryk]

Well after having it in the dead circuit pile for a while I decided to pick it back up and can't believe what I found... All the 330uf and 10uf caps were below 16v the 330ufs were actually 6.3v!! I believe that was why I was having power issues lol. I'll fix this soon as I get the new parts and post what happens. (Hate myself right about now for all the endless nights of trying to fix it)

[R.G.]

Well after having it in the dead circuit pile for a while I decided to pick it back up and can't believe what I found... All the 330uf and 10uf caps were below 16v the 330ufs were actually 6.3v!! I believe that was why I was having power issues lol. I'll fix this soon as I get the new parts and post what happens. (Hate myself right about now for all the endless nights of trying to fix it)

That would cause some problems, OK.   I've... um... done similar things. 

[aryk]

Alright so got the new caps in, checked the power rating and wired everything stock other than using the charge pump and was getting about 17.5 from that to the board. Turned it on and only got bypass in both on and "off" modes. Wondering if there's a draw up of where I should be getting audio with an audio probe? or possibly what my tranny's should be reading? I can post my values here in a few but wanted to ask if those things were available or able to obtain. (sorry I'm a pain...) Just wanting this circuit to come to life so badly! I even built a whole 'nother circuit and get the same results. The lamp isn't even lighting up. If this would help to narrow down something. Still sounds like a power issue to me.