Anyone build a Jen HF Modulator

[Tychobrahe1979]

I am curious if anyone has succesfully cloned this effect. I got a schematic of it from CJLectronics awhile ago and I built one. I just checked the CJL site and it is no longer posted leaving me to believe that maybe there was something wrong with the schematic. The reason I say that is because the one I built doesn't work. I cheked it out with a DMM and I am getting voltage everywhere, I checked my transistors out with the socket in my DMM and I am getting nearly the exact same hfe reading for each. I get no sound at all when I play through it. What I am saying is I've checked everything I can think of and so now I'm curious if anyone has built it and had the same problem. I am by no means an expert but I have built quite a few pedals succesfully. I would appreciate any input I can get on this.

[Paul Marossy]

Well, you could look at the schematic and see if there is any obvious errors. Perhaps there is one place where the signal path gets broken or something? Do you have a schematic that you could show us? That would go a long way towards figuring it out...

[Tychobrahe1979]

http://img19.photobucket.com/albums/v58/rcdan87/Jul_08_001.jpg


Here it is.

[Paul Marossy]

OK, I looked at the schematic. I can't see anything that jumps out at me as being a glaring error. I see that it uses some 2N5172 transistors, which appear to be just be general purpose NPN transistors. What did you use for transistors?

Here is a data sheet on the 2N5172:
http://www.fairchildsemi.com/ds/2N/2N5172.pdf

Maybe there is something in that oscillator section that is wrong. Maybe someone more knowledgeable than myself can chime in... now would be a good time.  :wink:

[Tychobrahe1979]

Thanks for the quick reply. I used the same transistors as specified in the schematic. I checked, checked and double checked to make sure they and the rest of the components were on the board correctly and that nothing was touching that should not be, including the traces. Thats why I am baffled because this is such a simple layout. I built an audio probe (the one found on Paul Morossys' site which is the same one I've heard talked about on this one) and went through the board but I think I am doing something wrong because from what I understand I should be hearing some noise from my amp as the positive end is moved through the board. Instead when I touched the positive to something it just silenced the hum my amp naturally makes. :? Yes I did ground the other end to the board. Things that make you go hmmmmmm.

[jsleep]

This isn't much help to you, but I tried building it a few months ago and I couldn't get it to work either.  It's still sitting on my bench for me to go back to someday.  I know at least one other guy who tried and failded to build one and _he_ had an original unit to help him out, he was cloning an original, circuit board layout and all.

My guess was that I need to work on transistor bias, etc, to get it working.

JD Sleep

[mongo]

This isn't much help to you, but I tried building it a few months ago and I couldn't get it to work either. It's still sitting on my bench for me to go back to someday. I know at least one other guy who tried and failded to build one and _he_ had an original unit to help him out, he was cloning an original, circuit board layout and all.


thats me! ;-D yeah, I tried cloning even the original PCB (wich was not very difficult I still have all my alyouts and pics if you're interested)

 I didnt make the thing to work,funny thing is that I heard the "ring modulation" on my clone without the guitar sound! it was kind of weird...

I tried making the PCB clone several time with the same result... there is something wrong with the schem or the transistors I guess...

Mongo

[jsleep]

Hi Mongo!

Haven't heard from you in a while.  I assumed in my previous post that you never did get it working since we last emailed.  I figured you would have let me know if you had gotten it working :-)

Thanks,
JD Sleep

[Paul Marossy]

I was thinking after my last post that it's probably a transistor bias thing. I suppose that you could replace the resistors involved with biasing those transistors with trimpots and tweak stuff until it sounds right. If the schematic is derived from the original circuit and is correct, it's gotta work.

The thing that puzzled me is that 2N5172, that's a new manufacture transistor. I'm sure the original unit probably had Ge transistors in it and may have biased totally differently from Si transistors. Maybe that is the part of the problem here? The other thing I thought was odd is that 33K to ground on the input. It seems like that would really hack your input signal.

I hope someone figures it out, it's kind of an interesting little circuit that I would maybe build if I knew it worked...

[mongo]

guess it's the transistors or something... as I said I cloned the EXACT PCB from the original, and it didnt work... same resistors, caps etc etc... and I used the transistors marked on the exact same schem that you have...

Andy

[Dan N]

Mongo, I bet I am not the only one who would LOVE to see your pics!

If it is not too much trouble, could you please send a top and bottom shot to me here:
(deleted in case of spam bots)

I can try building one over the wekend.

Thanks,
Dan

[jsleep]

Hi Dan,

I've got a layout for it, but I obviously haven't posted it, since it doesn't work yet.  Maybe I'll move this up my list and see if I can get it working so I can post the layout, etc.

JD

[Dan N]

Thanks JD, I'll look forward to seeing it!

Odd that it wouldn't work. I doubt that the workers at JEN were tweaking as the units rolled down the assembly line.

I see the 2N5172 is ECB. Of course, wrong pinout would be too easy...

Dan

[Zero the hero]

JD, can you send the layout to me too? If I have time I'll try to build this circuit to help debugging it.
Thanks!

[mongo]

Ok, first, a Pic of the original beast  beside a rarity: Mexican Pedal wiech is the same as the FOXX units, it's abeast and I love it, I dont know if you guys knew but a lot of "all american" pedals and synths were made in Mexico back in the day...

 Ok, I cant post pics here so I'm sending the images and my layout  to whoever want them...

Mongobigmuff...

[mongo]

Dan,

pics and  layouyts for my JEN modulator failes projects  are on your way...

[Dan N]

Thanks mongo!

Or merci!

Or gracias!

I'll give it a try.

Dan

[Paul Marossy]

Did you use a socket for your transistors? If you wired it for a transistor that has the "standard" EBC pinout, then an easy test would be to place a transistor with a known EBC pinout and see what happens. In your case, with nothing at all, I would suspect a wrong pinout. The thought never crossed my mind about the pinout thing, most transistors are EBC...  :shock:

[Dan N]

I'm still fooling around trying to get the pcb and parts to match the online schematic. It really looks like the 220K resistor off the center of the intensity pot in the schematic goes to the wrong place?

If anyone has this on breadboard, try moving that resistor from the base to the collector of that transistor.

Anyway, onward...

[mongo]

get it working!!! because I made my original HF modulator sick in order to make the clone...


hey if you think it can help I'm willing to ship  to you  the ORIGINAL PCB to you if this helps the cloning of  it...


 Andy in Paris (altough I'm Mexican in mind and heart...;-D)