Anyone build a Jen HF Modulator

[puretube]

...most transistors are EBC...

http://www.fairchildsemi.com/ds/2N/2N5172.pdf

[Paul Marossy]

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

Dan"

Yeah, I looked up that data sheet when I first saw this thread, but I didn't notice the different pinout - it just never crossed my mind. The base on most transistors is the middle pin on most transistors, right? The 2N5172 is somewhat of an oddball as far as pinout is concerned...

[puretube]

let`s assume the schem is correct, and the transistor`s pinouts are ok:

are you sure to have the right cap values (around the input)?
(the input section around the tone control looks rather suspect to me:
very low impedance for a guitar-gadget....I`d rather stick a cassette-player to the input...)

Take out the 0.22µF on the right side of the output-jack:
this disconnects the oscillator and attenuator section from the preamp.
Now you should hear your guitar loud and clear.
If you don`t hear it, s.th. is wrong around the first transistor.
If you hear it, s.th. is wrong with the oscillator and/or the attenuator.
It would be nice to know if the oscillator is running.
You could, for a short test, run a wire from the collector of the rightmost transistor through a 0.22µF cap and a 1M resistor to your amp -volume down!!! - do you hear some tone, or throb?
If not, the osc. doesn`t run.
What`s the value of the resistor parallell to the speed-pot?

[Tychobrahe1979]

I tried your suggestion of --You could, for a short test, run a wire from the collector of the rightmost transistor through a 0.22µF cap and a 1M resistor to your amp -volume down!!! - do you hear some tone, or throb?
There is no tone or anything at all. I know this would be to easy but I am curious what the original transistors were. This is truly a great mystery.  Hmmmmm :?

[mongo]

I have the original Hf modulator as I said... how can I chack out what transisotrs it has? i know this is probably a stupid question but is there any way to find out this?

[Paul Marossy]

"I have the original Hf modulator as I said... how can I chack out what transisotrs it has? i know this is probably a stupid question but is there any way to find out this?"

The transistors themselves are usually marked by the manufacturer with a model number, unless Jen was in the habit of trying to hide what components they used by obscuring identifying markings...

[Dan N]

There should be some numbers around the skirt of the transistors. From the photo, it looks like Q1 is different from the others. Look like '70's organ transistors to me.

O.K. The schematic is wrong. The 220K resistor from the wiper of the intensity pot should go the the collector (not the base) of the oscillator. And, as puretube saw, the input is messed up. The guy who traced it got the pot wrong. The wiper should be going to that big (0.22) cap, lug 1 to the 33k/3300pf, and lug 3 to the .01/33K junction.

Mine kind of works. That's not saying much, but it does get some weird stuff when the speed and intensity pots are set right. It likes being boosted with the treble booster from my Beebaa.

Here are a couple of Mongo's photos:

http://users.rio.com/senorris/JHF/originalModulatorR.jpg
http://users.rio.com/senorris/JHF/withoutpotsR.jpg
http://users.rio.com/senorris/JHF/Mycopy.gif

I used med gain transistors. Think I'll try higher, starting with Q1.

Dan

By the way, Mongo, is that just a jumper hiding behind that blue cap? Thanks.

[Paul Marossy]

"O.K. The schematic is wrong. The 220K resistor from the wiper of the intensity pot should go the the collector (not the base) of the oscillator. And, as puretube saw, the input is messed up. The guy who traced it got the pot wrong. The wiper should be going to that big (0.22) cap, lug 1 to the 33k/3300pf, and lug 3 to the .01/33K junction."

Dan,

That whole input section looks really screwy to me. I think you're right about the tone control. But, that 33K to ground on the input just doesn't look right to me, it seems to me that the input signal strength would take a massive hit, IMO. Those transistors physically look just like the ones in vintage CryBabys. Anyhow, if you do get it working, can you whip up a revised schematic for us? It sounds like you are almost functional...

[Dan N]

It sounds like you are almost functional...

If I had a nickel for every time I heard that...

How's this look?

http://users.rio.com/senorris/JHF/hfmod1.0.gif

Kind of like the tone circuit in a Big Muff or SD9.

About that 33K resistor, from the photo and original trace it looks accurate.

[Paul Marossy]

OK, looking at the revised schematic, that 33K looks like it's supposed to be there. I hope you do get it working, I am interested in what this bugger sounds like.  

[mongo]

By the way, Mongo, is that just a jumper hiding behind that blue cap? Thanks.[/quote]

Yes... it's a jumper...


 And by the way, for those curious of how this thing works, there are some decent samples at:

http://www.tonefrenzy.com/2/jen_hf_modulator.htm


 Mongo

[jsleep]

I can post your pictures, I think I still have some you sent me

JD Sleep

[mongo]

yes please do it

[jsleep]

Dan, Paul, Pure,

You are the MEN!!!!

Dan your corrections are uhm, correct as far as I can tell, Paul the schematic revised is correct.  I applied Dan's revisions an mine works now and sounds like the Tone Frenzy sample!  This is very cool!  I'll revise my layout and post a project for this very soon.    Cool noise maker toy, probably not a wide appeal to everyone, it's sort of a one-trick stompbox.

I did use the 2N5172 transistors, I suspect other types would work, I have sockets on my prototype boards so I can verify that.

Thanks all,
JD Sleep

[Paul Marossy]

Awesome!!  

I'm going to have to listen to that soundclip now at tonefrenzy now...

[Dan N]

That's good news JD!

The original has a big ass cap across the power supply that was not in the original schematic. You might want to find the value of that from Mongo to add to your layout. I used a 47uf.

Sure hope this helps Mongo get his up and running!

So, what next?!?

Dan

[mongo]

this is great new!!!! I'm happy my  help was worth something here...;-)

 but my doubt persists... why didn't my clone never ever worked? I copied EVERYTHING from the original  and not only once! I made and populated at least 4 layouts and never got the thing to make a sound...

I could hear the effect without the guitar  sometimes and I could hear the pots "changing" the sound while I turned them... bad jack wiring maybe? mmmh...


 Looking forward to that improved layout, JD and thanks again  to everyone!!!

Oh, man I just LOVE this forum...

[jsleep]

Hey Mongo,

Can you give us the value that filter cap?  Big cap from power to ground.  If you want, you can send one of you non-working boards to me and I can look at it for you to see if I can figure out what's wrong with it. I don't know if you want to bother sending internationally.

Thanks,
JD Sleep

[mongo]

I'll do it!!!! do you want a populated layout? where do I send it?


Thanx!

Andy

[mongo]

about the cap... is the big blue one?   I need a quick tutorial on how to read caps... I have  a big problem, I am COLORBLIND! I can  indentify resistors somehow easly, but I've always double checked  with a  multimeter... is there any way to do this with caps as well?

sorry for the semi-dumb inquire but I learn as I walk here ;-D