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So, any thoughts guys?

I tried that, but the result was the same, it doesn't blink as it used to. I noticed that when i plugged the dc power, the lamp "flickered" a bit before it stabilized, don't know if that indicates something in particular. Well, any thoughts?

Hi guys,
So i had my harbinger working for a couple months now, not perfect yet tonewise, i think i might change it's photocells. But today, when i was jamming a bit using my pedalboard, i noticed the harbinger had stopped working, and the rate led was not blinking. I opened it and as it was obvious, the lamp was not blinking either. When i decrease the speed knob, the only thing that happens now is that the lamp loses a bit of brightness more or less from 10 0'clock, to the lowest speed. So, anyone knows what might be causing this sudden issue? Can it be an active part that broke? If so, some voltages might be useful, so where would i start, if that's necessary?

Best regards

Aparently i slved the problem for now, but i'm not certain of what was causing it, since i tried a couple things at the same time. It sounds like it's working properly, but if it decides to stop working again, i'll repost here again. In the meantime, thanks for the help, and take care!

Now i noticed something strange. When i usually disconnect my wallwart from power, while keeping the daisy chain in my pedals, their leds turn off slowly, but it happens in a instant, now i did that with the hipster, and the led didn't turn off, even thought the wallwart wasn't connected to the power. I know that the power supply hold a bit of energy till it dissipates, but it doesn't last that long, almost as if the energy is being hold in the pedal somewhere. Also, i noticed the pedal sounds just like when i played him once with an almost dead battery, so i assume the problem is somewhere in the power zone, but not in the dc, because the mangler works like a charm. So, any thoughts?

Hi Rafa. I'm sure you know this, but when a non-boxed, working effect suddenly stops working once it's in the box is almost always a result of a short or something coming loose in the circuit. Take the circuit back out of the box and A. See if it's working again or B. If it's not working, look for loose wiring.  If nothing is readily apparent, take some voltage readings and see if you are losing voltage somehow. The fact that your transistor can't be biased correctly can easily be a case of it not receiving the proper voltage in the first place. If you want, post some pics and we can take a look with you. I hope this helps as it sounds like you really liked this circuit before you boxed it. Good luck....will follow this thread.

Steve.

Actually, that's not the case, i had it box for a long time now, but i always thought that it oscilated to much past the 3 o'clock on the fuzz pot, so i changed the ceramic capacitor c2 to 100pf, and adjusted the bias again, in the end it was working perfectly, in the box already. After i screw the back and installed it in the pedalboard, it started having issues right away, the ones i said earlier, i took the back again, and the issues were still there. I totally forgot to mention that this is in two-in-one box, with a mangler on his side, working properly, and they worked both fine till yesterday.

Hey guys,
Yesterday i decided to swap the C2 from my hipster fuzz, from 10pf to 100pf, because i though it sounded better, without that big oscilation at the end of the fuzz sweep, and it was working perfectly, the bias well adjusted to 4.5v. Then i closed the enclosure, connected it to my pedalboard (cables, daisy chain, all that stuff) and the first time i engage it, it sounded really really quiet, like a fuzz on the backgroung when i played the strings. I took it from the pedalboard, tried it alone and open again, the same issue continued. I checked the bias again, and the best it can go now is to ~1,0v, and when i put it in that value theres a big static noise from it, the guitar almost silent. Did something happened to my trannies? Which by the way are a BC108 and a BC108C from a banzai kit.

Best Regards

I've tried a ton of ways of actually covering a photocell to cover it, with kind of poor results. Electrical tape seems to still bleed through some light. This might be more trouble than it's worth, but some heat shrink over electrical tape might work. In the end, it could be simpler to desolder them.

Those photocells will be more like 5-10K for light resistance under most circumstances. It's low enough and in line with what I've heard of people measuring in vintage units. Like I said, if you want to fake a lower light resistance, you could always lower those 47K resistors.

Ok then, thank you for the advice, i'll try everything you said, and i'll post here again soon!

Measuring the photocells would be almost impossible in-circuit. To do that, you'd need the cover off, which means light is getting on the photocells, so there's no way you can measure the dark resistance or the actual in-use light resistance.

Umm... Silly question, but you ARE testing the effect with the circuit in total darkness, right? I usually put a cardboard box over my test rig and turn out the lights.

In case i decide to go for those photocells from smallbear you referred, which ones are you talking about:                         http://smallbear-electronics.mybigcommerce.com/photocell-silonex-advanced-photonix-hi-dark/
or http://smallbear-electronics.mybigcommerce.com/photocell-silonex-advanced-photonix-hi-dark-to-5/ ?
And also, could i ask for a kit with 4 of those matched to those values you referred? Or would i need to get a couple and match them myself, which would be much more expensive, i think.

Those are the same photocell. If you're planning on dunking your Univibe in slightly acidic water fairly often, you might want the hermetically sealed version. (But I get those because they look cool.)

Re the Banzai cells, I'm not even sure what matching would entail for this effect. I suppose one could match response times, but I sincerely doubt that's what Banzai's doing because it would be very difficult. You could match dark resistances, but that doesn't strike me as meaningful. I guess you could match them to some range for on/off resistances, but they don't tell you what they've matched them for.

Couldn't i put some tape on the photocells and measure them? Would that work? Or is better to desolder them? Also, to measure the minimum on dark resistance, i measure them completely in the dark, but what about the maximum off resistance?

About the matching, you were saying earlier that getting photocells with 1k was better for a good sound, so are those smallbear photocells close to that, or do i need to search for those values in various photocells of those? Or could i even ask someone from smallbear to get me 4 of those with 1k minimum resistance (if i can even do that)?

EDIT: And yes, when i change anything of the trimmers or measure something, it's completely in the dark, but from what i've seen around the web, it's not that silly of a question, believe me!

I'm always leary of trying to replicate something I hear on a record. The one thing you can't account for is who knows what they did in the studio and if there is one band that did a crap ton of stuff in the studio after recording a song it was Pink Floyd. So whether it got tweaked after Gilmour recorded Any Colour who knows for sure.

Just a thought FWIW.

Yeah, exactly the way i think, the only thing i was saying is that my univibe doesn't feel strong at the highest speed, and maybe that's the way they work, i don't know

There are multiple things going on here.

One is the lamp. If you've used the specified lamp, you'll be fine for the entire speed range of the pedal for normal operation.

The other is the photocells, and this requires really careful parts selection, because they have several different properties, none of which are particularly easy to measure. But this is one place you might want to experiment if the rest of the circuit is definitely correct and you have already been very careful about dialing in the trim pots.

1. Switching range. This is the total range, in the circuit, between fully on and fully off for the photocells.

-Minimum on resistance: You want a low on resistance -- 10K is okay, 5K is great, 1K is spectacular. Lower resistance means that more out of phase signal gets mixed in, which creates a more intense effect. There is actually something you can do in-circuit to help if your photocells have too high a dark resistance, though! See those 47K resistors in series with the photocells? Make them smaller, e.g. 22K. You can even jumper them.

-Maximum OFF resistance: This is the opposite -- you also need a point where the out-of-phase signal is pretty much completely taken out of the circuit. Since the photocells are beating against an impedance of about .. 38K in each stage, you need a photocell that can reach multiple megaohms to achieve that. While it's not too hard to find a cell with 1M maximum dark resistance (like Tayda's), those cells won't get anywhere near the maximum in the actual circuit, especially when the bulb is going fast and not going completely dark. So you have to go higher ... The Silonex 7532 was pretty popular, but as Smallbear noted, at some point the construction technique changed and they went from being a cell with 20M, 50M, or even higher to rarely reaching 10M. So Smallbear had a version made called the "hi-dark" that hits 200M when fully off. You won't HIT fully off, but you will get way higher resistance on the dark cycle if you use those. There's not really anything you can do in the circuit that will fix things if your dark resistance isn't high enough.

2. And the rise and fall times.

-The Rise time is how long it takes for a photocell to reach some percentage of its maximum dark resistance. Just like how your eye might have an afterimage when exposed suddenly to a bright light, a photocell will retain some light memory. A faster rise time means that the photocell will "forget" the lamp's brightness -- this is absolutely critical to retaining a deep effect at faster speeds. For reference, one of the fastest devices out there, the VTL5C1, still only has a Rise time of 30mS (and I haven't found anything like that in a discrete photocell, though I really wish I could!). The hi-dark that Smallbear carries is more like 70mS, I think. That's only about 14hZ before the light blinking on and off has almost no effect. While the Univibe's maximum speed is probably only about 10Hz (and it might even be more like 8Hz stock), that's still getting pretty close even in a photocell that's basically made to drop into a Univibe.

-Fall time is how quickly the photocell drops to its lowest resistance. This depends on whether the light is bright enough to actually drop it there. Remember how I said that you want an extremely low resistance? Well, now you have to contend with the fact that the light needs to be bright enough to drop it there and on long enough to actually get it there. So you want to add this time to the Rise time ... if you get anything more than 100mS, you're at the point where the effect will be very shallow at faster speeds. You're fighting physics in that case and no changes in the circuit will help you.

I haven't even touched on proximity, which can vary according to photocell.

And this is just a tiny portion of why this can be such a complicated build ...

I don't know how to measure rise and fall times, because it's hard to set up good testing conditions. I think you could make a small box with some tiny holes in it and a light inside, put the leads through with the cell on the inside, close the box, and measure the leads, but your multimeter will have to be very accurate.

Thanks for the time you took for that explanation, really helpful!

So if i intended to measure the minimum and maximum resistance of the photocells i have installed, which by the way, are from a univibe kit from Banzai, could i do it with them on circuit? And how would i do it?

About the rise and fall time, i really doubt i could measure them, my multimeter is really basic, and i don't think it is fast enough to measure that.

In case i decide to go for those photocells from smallbear you referred, which ones are you talking about:                         http://smallbear-electronics.mybigcommerce.com/photocell-silonex-advanced-photonix-hi-dark/
or http://smallbear-electronics.mybigcommerce.com/photocell-silonex-advanced-photonix-hi-dark-to-5/ ?
And also, could i ask for a kit with 4 of those matched to those values you referred? Or would i need to get a couple and match them myself, which would be much more expensive, i think.

I'm always leary of trying to replicate something I hear on a record. The one thing you can't account for is who knows what they did in the studio and if there is one band that did a crap ton of stuff in the studio after recording a song it was Pink Floyd. So whether it got tweaked after Gilmour recorded Any Colour who knows for sure.

Just a thought FWIW.

Yeah, exactly the way i think, the only thing i was saying is that my univibe doesn't feel strong at the highest speed, and maybe that's the way they work, i don't know

I finally got to do the mods to my Harbinger. So these are the results.

Moving to 4.7k for R46 does seem to help to me. I think it helped in being able to dial the gain into a better setting.

I put R41 and R44 at 1k. I did this because I can use the CV control section to put the minimum resistance where I want it to be. But, I did try it with the normal 100kC pot in there first. 1K is too small. It gets too fast for the lamp to even respond and then going further CW just locks up the LFO. I'd guess that a 2.7k resistor for these two would be about as fast as you'd want it to go. With the CV controlled board in there, I have the smallest resistance at about 3.3k and that goes plenty fast for what I want.

The depth and strength of the vibe or chorus stayed good and strong up to the point where the lamp really couldn't respond fast enough, so it should be fine to reduce those two resistors to get a faster LFO going.

I still haven't tried to reduce those resistors to get it to go faster, but i'll try it too someday. I'm still not satisfied with it, i tried to reduce the 47k resistor to 4,7k and it started to work better, the lamp was brighter, and sounded more intense, but as i roll the speed control all the way, it also looses intensity, it seems like a vibrato, not close to the strong effect of gilmour in "Any colour you like", and i think if i get it to go faster, it'll be even more subtle. So my question is, is this what is suppose to happen, is it suppose to be a little more subtle at high speeds, or should i try to swap my photocells? Or could this be just a matter of trying to tweek the gain and offset a little further?

Thanks for the answers. About the leds, i think i'm going to swap them to see if the problem is the led or the circuit, i'll update the post then. Cheers!

Hi guys,
So i finished a two-in-one pedal, with a green bean and a green russian mudbunny, and i'm experiencing a couple things that i want to ask if they are normal. So, i used two red leds and three 1n914 for the green bean clipping, and one of the issues is that i hear a big volume drop when i change from the red led's to the 1n914 clipping, is this normal?

The other issue is that i used two identical green leds and resistors for the on/off of the pedals, and the green led from the mudbunny is not as bright as the green bean's. The mudbunny is the 2013 version, the one that doesn't have a led spot on the pcb, so it is wired as the standard wiring diagram. On the other hand the green bean has a "led" spot for the positive lead of the led, so is this why it is brighter? Or is something wrong with it?

Best regards 

Thanks for the suggestions brian, really helpfull. Just another question i forgot to ask: how could i know if one of the cells got damaged during the soldering and other stuff, or even arrived broken, would it even work with just 3 cells, or would it have sound but not the sound a univibe should have? And how could i spot this?