Hello there,
As you might know, EdJ and I are trying to build JC Maillets Univibe+.
http://www.lynx.bc.ca/~jc/pedalsUnivibe.html
Well, we're having a little trouble reading JC's drawings, so Ed made a few notes and some fresh drawings himself.
He has a few ideas he'd like to share with you, but his new computer refuses to post here, so here goes:
The jumper between the 250k trimmer and the Collector of the 2n3904 and between the Emitter of the 2n3904 plus the 250k trimmer AND the 500 Ohm trimmer need to be replaced by 100k resistors.
Like in JC's the darlington mod to the bulb-driver circuit:
http://www.lynx.bc.ca/~jc/UnivibeCloneDrvrMod.gif
What do you think ?
Thank you, also on behalf of Ed,
Vincent
V!N & Ed,
Quote from: V!NThe jumper between the 250k trimmer and the Collector of the 2n3904...
I built jc's univibe+ stock, as is, including the jumpers exactly as they are shown in the layout. Sounds great!
Quote from: V!N...and between the Emitter of the 2n3904 plus the 250k trimmer AND the 500 Ohm trimmer...
I'm not seeing the emitter of either of those transistors sitting on the same (ground) trace as the one with the jumper between the 250K and 500 Ohm trimmers. But, whatever... Like I said, if you build it as shown it should work great.
I guess you could add those 100 Ohm resistors if you really wanted to. But, I think you'd have to cut some traces to do it, and I'm not sure what the benefit would be.
Make sure you have those trimmers set at max resistance when you power it up for the first time, or you might blow the lamp. Good idea to have a few spares just in case.
Good luck!
~ Charlie
I can't find the bulb that he calls for. What would be a good replacement??
Thanks,
Mike
I don't know any specific mfg or part #'s. But, I would try anything with the same specs: 1.5V @ 25mA :idea:
~ Charlie
Hi,first i must say that it is great being able to post again!
Charlie,i am sure your unit sounds great but i would like to know if there is a difference if the 100 K resistors are used in stead of the wires.
JC,can you enlighten us,please?
Thanks in advance,Ed
Ed, Vincent ...
I just finished re-doing my Vibe page and should have made things more clear (I hope) ... I drew a pic of the circuit mod where my "Offset Adjust" control consists of a 100k trimmer flanked by two 100k resistors on both sides (for limited range) ... in the last few units that I built I simply used a 250k trimmer and the two 100k resistors are replaced by shorts - it makes no difference functionally as long as the overall DC impedance to ground isn't lower than 47k as in the original circuit ... this mod will help accomodate bulbs in the 25mA - 40mA range (smaller is better) ... let me know if the adjustment procedure is not clear ... I also uploaded a clip of my Vibe in action to give an idea of what it can sound like ...
http://www.lynx.net/~jc/pedals.html
... jc
Hi,
i have got mine working now.
Vin`s will follow i`m sure.
There is one thing that i just don`t get;on schematics of the Vibe i see a 1uF cap going from each cell going to the emmitters of the different trannies(o.k. reverse that sentence:).
On the layout i only see that at 1 cell,the other 3 are going directly from emitter to cell.
Can someone please explain that?
Thanks very much in advance!
Greetings,Ed
p.s.it is sounding great!
Right on Ed ! :D
I finally got my bulb to light today. Now all I've got to do is make it blink. ;)
For the lightshield i am using a 20 cc syringe.
It fits neatly and has flages(that you have to trim somewhat otherwise it won`t fit)that makes it easy to make it removable if you use 2 little screws.Use a thick black marker or black paint to paint the outside.
Glue in a piece of aluminium foil and you are in business.
Greetings,Ed
Quote from: EdJOn the layout i only see that at 1 cell,the other 3 are going directly from emitter to cell.
... good observation Ed, notice that in the schematic the "in-phase" branche in the all-pass filters contain three elements in series: a 1uF cap, a photocell and a limiting 4k7 resistor ... since they are in series and there are no inner side branches they can be permutted in any order and it won't affect the way the circuit operates ... in the later three cases the order is changed relative to the schematic in order to make best use of real-estate on my pcb board ...
glad you got it working - cheers, jc
Hi,
Your mods seem to be a very good improvement to the Univibe circuit .
Can i try a MPSA13 to the place of the two 2N3904?I'm looking to the Silonex Cells but i don't know the good reference ?Thank in advance
Regards
Bruno
Thanks JC!
I see what you mean now.
I didn`t think your pcb was wrong or anything;i was just wondering what happened to the caps :)
Greetings,Ed
Bruno, I haven't tried the MPSA13 but I got feeling it would work as long as you're not powering a bulb that requires more than 30mA to turn on ...
I posted a few potential cells on this thread :
http://diystompboxes.com/sboxforum/viewtopic.php?t=993&highlight=cells
Small-Bear Electronics carries the Silonex NSL-5152's and NSL-5542's though I haven't tried them yet ...
8):idea:8) ... jc
Hi,
Thank you very much for the infos!I'm going to try the MPSA mod and to buy some Silonex at RS Components. I'll post you the results .For instance ,i use cells unmarked from my electronic shop,but i'm not very happy ,the rise time looks too long or too short ,release time too ,but it seems to be the wrong values .
Regards