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DIY Stompboxes => Building your own stompbox => Topic started by: eh la bas ma on February 11, 2021, 11:33:48 AM

Title: Lectric Fx Dandy Horse: Buffered bypass question
Post by: eh la bas ma on February 11, 2021, 11:33:48 AM
Hello,

I would like to wire the Dandy Horse in buffered bypass.

I am not sure how the buffered bypass switch should be wired.

On my build, I used a SPDT toggleswitch. it allows to silently switch on and off the effect when the main footswitch is On. There is only a clean signal on one position, and the modulation is activated on the other position. I asked Lectric Fx and this is the answer i received today :

"You would use the buffered bypass if you want to build the effect the original way it was made by EHX.  And it would be instead of the 3pdt true bypass.  There would  be no reason to  use both.
In other words, we made it true bypass for the Dandy Horse, but also tried to include instructions to build it the "old" way, if so desired."

I am still confused. "it would be instead of the 3PDT true bypass" ?

http://lectric-fx.com/wp-content/uploads/2017/03/Dandy-Horse-V.1.0.pdf

"For buffered bypass operation the two wires from the SW1 pads need to be connected to a latching SPST switch (DPDT if you want a status Led)"

I guess I can't use a toggleswitch, but can I use a classic 3PDT ?

Every pictures I could find on the net are showing this circuit in true bypass, so I don't have any exemple.


How should I do the wiring with the SW1 pads ?




(https://i.postimg.cc/4YDWdqXR/IMG-20210211-170004.jpg) (https://postimg.cc/4YDWdqXR)

Thank you very much for your help.
Title: Re: Lectric Fx Dandy Horse: Buffered bypass question
Post by: iainpunk on February 11, 2021, 03:41:48 PM
just use one of the switch poles of the 3pdt on the SPDT's location, and wire the jacks directly to the boards in and out, not through a bypass switch

cheers
Title: Re: Lectric Fx Dandy Horse: Buffered bypass question
Post by: eh la bas ma on February 11, 2021, 05:06:21 PM
Ok, thanks !

I have an extra hole in the enclosure and I would like to know if it is possible to put a Led there, synchronized with the modulation's speed.

I 've been reading this thread about adding a LFO led in a Bloodstone phaser:

https://www.diystompboxes.com/smfforum/index.php?topic=118168.msg1099399#msg1099399

I understand it could mess up the sweep, but i am willing to try.

I guess the ICs generating the clock frequency are the two MN3007. I checked a datasheet :

https://pdf1.alldatasheet.fr/datasheet-pdf/view/14235/PANASONIC/MN3007.html

 It looks like i should follow the signal from pin 2 and pin 6, in order to connect the Led somewhere along the way.
 On the Dandy's schematics, these pins are going to something called "Net 107, 108, 112" and "Net 113" . Any idea what it means ?
Title: Re: Lectric Fx Dandy Horse: Buffered bypass question
Post by: iainpunk on February 11, 2021, 08:17:54 PM
IC8 pin 14 - 2.7k - LED - GND

and add an extra 100nF cap as close as possible over pin 4 and 11, this takes some possible ticking away.

cheers
Title: Re: Lectric Fx Dandy Horse: Buffered bypass question
Post by: eh la bas ma on February 12, 2021, 12:50:21 AM
It's working !

Thank you very much !

The flashing Led is really helpfull to control the speed rate and to operate the whole unit, it's a welcome addition.

There isn't any ticking, except when the Blend switch is set on modulation only. The 100n cap, connecting pin 4 and pin 11, doesn't reduce it very much. I tried 220n with no significant result.

 I removed the "speed Led" and the extra cap, the clock is still audible when the clean signal is switched off : It's not the Led, I may have created a short somewhere recently.

I am trying to locate it near IC8, I will find it.

Title: Re: Lectric Fx Dandy Horse: Buffered bypass question
Post by: iainpunk on February 12, 2021, 09:37:43 AM
have you tried a 10uF cap, maybe there is to much wire length between the IC and the cap and residual inductance might cause a dip in power throughout the IC. if the tick is to bad, an Electrolytic cap would work.

cheers, Iain
Title: Re: Lectric Fx Dandy Horse: Buffered bypass question
Post by: eh la bas ma on February 12, 2021, 03:42:34 PM
I feel more confortable in classic true bypass mode to eliminate the ticking, so I put it back together.

I tried a 6.8uf and 15uf electrolytic (that's what i have in reserve) but it's still the same. I connected the positive leg on pin 4 and the negative one on pin 11 (from this datasheet : https://html.alldatasheet.fr/html-pdf/557726/TI/LM324/22/1/LM324.html ).

Isn't it strange that the ticking is still there when i remove the cap and the extra Led ?

I can't find any shorts and the modulation is allright. There isn't any wires on IC8, just a 2.7k resistor soldered to the Led, wrapped in plastic shielding, as you can see on pictures :


(https://i.postimg.cc/HjmdVGGm/IMG-20210212-211826.jpg) (https://postimg.cc/HjmdVGGm)

(https://i.postimg.cc/xkHV15tq/IMG-20210212-211902.jpg) (https://postimg.cc/xkHV15tq)
 
I tried different grounding options for the Led (Footswitch, Jack In, power jack, board...) and it sounds like the ticking is reduced very slightly, using the pcb's ground.

Now i'm thinking about replacing the LM324, maybe it has been a bit overheated, but again, the modulation is still fine except for the clock ticking on one side of the Blend switch. I will try to restart the calibration process, just in case, and a bigger capacitor.
Title: Re: Lectric Fx Dandy Horse: Buffered bypass question
Post by: eh la bas ma on February 12, 2021, 03:48:16 PM

(https://i.postimg.cc/ZvN7hYmQ/IMG-20210212-214441.jpg) (https://postimg.cc/ZvN7hYmQ)