Jennings Harmonic Boost info and schematic wanted

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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bajaman
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Post by bajaman »

Hi folks
I have in my hot little hands - a JENNINGS ELECTRONIC DEVELOPMENTS Dartford Kent England HARMONIC BOOST pedal.
Okay okay - I will take some photos to share with all of you , especially AG - he will like this one :wink:
BUT - It has been mutilated unfortunately and no longer works correctly - does any one have a schematic for it?????
The label on the bottom has the serial #02124. also the label shows 3 footswitches in a triangular formation- harmonic 1 switch, harmonic 2 switch and a centrally mounted harmonic 3 switch (the only switch working at present).
There is a rotary foot pad control which sweeps the poti through it's entire 270 degree rotation. i have never seen one of these before - it is in a light grey coloured hammerite finish case, and is similar to the Jennings SCRAMBLER in case shape - has any one seen one of these - a rotary foot pad wah wah pedal :wink:
Anyway the Harmonic Boost label also has - "this unit is protected by patent applications nos. 15698 and 58809 and others pending throughout the world".
It appears to be a treble boosting fuzz face type circuit with two BC108 transistors. any and all help appreciated in restoring this baby back to original specs.
cheers
bajaman
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Post by analogguru »

Yes, the poti is a funny construction....

Guts would be interesting... especially in suporting you with selected additional infos.... I have guts from the Cyclone, Fuzz, Growler, Repeater, Wah-Wah and Wah-Volume

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Post by toneman »

some pictures here--

http://filters.muziq.be/model/jennings

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Post by bajaman »

bump - still searching for info :hmmm:
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Post by toneman »

an LPB1 equivalent??

post some pics of what U have. Inside and outside... :mrgreen:
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Post by bajaman »

pictures will be no use sorry - someone has already canabalised this many years ago :(
From what I can make out it is a silicon fuzz face type circuit (big surprise :lol: ) with three footswitches.
I am picking the middle footswitch is the bypass, but would like to know how the other switches are connected.
The rotary heel treadle appears to be controlling the high frequency content in the feedback loop.
Any help with the schematic most appreciated.
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Post by toneman »

didn't notice before, but discofreque has a front pic of the Harmonic Boost.

yes, it has 3 switches......

http://www.effectsdatabase.com/model/je ... monicboost

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Post by bajaman »

3 footswitches - BUT no volume or tone controls :hmmm:
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Post by jrod »

Isn't the volume controlled with the round foot pad?

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Post by bajaman »

Isn't the volume controlled with the round foot pad?
Is it?
An owners manual or operating function description would be nice to have - i have searched for one in vain - Discofreq is the only one I can find with any info - just a top view picture :cry:
I will keep searching - obviously swivel foot action didn't take off like Jennings hoped it would - the Cry Baby success took care of that :wink:
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Post by jrod »

:lol: Yeah, I can see why that volume control never caught on!

I wonder if there is any relation to the Gretsch Play Boy[/url] or [url=https://www.effectsdatabase.com/model/samash/harmonbooster]Sam Ash Harmon Booster? :hmmm:

A couple of those Jennings pedals share the same circuit with other pedals, so maybe this one does, too?

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Post by bajaman »

thanks :thumbsup but this pedal has no controls except the foot swiveller and three footswitches :wink:
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Post by Old Gregg »

Hope this might help some, got them from this fella at TGP http://www.thegearpage.net/board/showth ... p?t=963467

Also has a Repeater, will upload in a seperate thread.

Cheers
Attachments
Jennings Harmonic Boost Guts 1
Jennings Harmonic Boost Guts 1
Jennings Harmonic Boost Guts 2
Jennings Harmonic Boost Guts 2
Jennings Harmonic Boost Guts 3
Jennings Harmonic Boost Guts 3
Jennings Harmonic Boost Guts 4
Jennings Harmonic Boost Guts 4
Jennings Harmonic Boost Guts 5
Jennings Harmonic Boost Guts 5
Jennings Harmonic Boost Guts 6
Jennings Harmonic Boost Guts 6
Jennings Harmonic Boost Guts 7
Jennings Harmonic Boost Guts 7
Jennings Harmonic Boost Guts 8
Jennings Harmonic Boost Guts 8
Jennings Harmonic Boost Guts 9
Jennings Harmonic Boost Guts 9

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Post by Old Gregg »

Some info on the workings of the unit

The Harmonic Boost is a mid-range boost - the 'swiveler' adjusts gain, as far as I can tell the LH switch does bypass, and combinations of the other 2 switches set the boost frequencies. It's sort of like a wah with 4 fixed settings.

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Post by bajaman »

Hi folks
I am still looking for the schematic for this unit - according to the pictures it looks like a standard wah wah module similar to the Vox part #09-3786-0 as used in one of their Starfire guitars in the mid 60s. The three harmonic switches are all connected to ground on one side and presumably to capacitors or resistors on the small module board - must have been a real "russian roulettte" guessing which switch was engaged :roll: :roll:
The unit i have has been severely modified (butchered) in it's past life - the inductor has long since gone and the circuit represents a really bad gated fuzzface :slap:
I can rebuild it okay as far as the wah is concerned but would love to know how the three switches are connected from ground to the individual points on the PCB.
Any help is always appreciated. :hug:
Cheers
bajaman
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Post by Richard_Woolley »

Hi there
I have one of these pedals in pretty much original condition.
I will pop it open and see if I can take some photos of the circuit for you.
Mine works just like it did when I bought it back around 1975, good top booster for driving a clean valve amp like a Fender or a Vox (no surprises there)

Give me a day or two.

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Post by Richard_Woolley »

Wiring.jpeg
Circuit base.jpg
Here are some bits, photo of the underside of the circuit board and my poor drawing of the pedal wiring.

Originally it had a round 9v battery with the connections at either end. Sometime in the 90's I stopped finding that style of battery so changed the connections to the ones for a standard 9v as used in current pedals.

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Post by bajaman »

Hello Richard
Many thanks for the connection diagram and the track side of the pcb. :wink:
If it isn't too much trouble, would you please supply the capacitor and resistor values - from the previously posted images i can make out a.0047uf capacitor and a 330k (and possibly 3.3k) resistors. It would be real nice to know the greencap values as well as the other resistors.
Many thanks :thumbsup
Cheers
bajaman
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Post by Richard_Woolley »

ok, might be a few days before I can get the time to do that but will try my best

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Post by bajaman »

Jennings Harmonic Boost.jpg
Here is a preliminary sketch - missing component values would be great :wink:
NOTE: no bypass function - it is on at all times - just a single transistor boost with a three footswitch tone shaping section on the output - the swivel control sets the boost level :wink:
cheers
bajaman
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