freestompboxes.org

moved from 'Request Folder' to
Board index » Circuit Analysis » Modern Stompbox Effects (1975 - ...)

Most of this generation DODs have schematics all over the internet ...

still any schematic for that pedal ?

....it appears that the 6mm switch has been replaced,possibly wrongly oriented-remove it and turn it 90 degrees and solder it back on...I've repaired this replacement error several times for diy friends that don't understand the internal connections of this switch..........dr

DOD - FX22 Vibro Thang GUTS - no schema yet?

Why not let someone write to the DOD Technical Support? I asked them about the schematics of DOD Big Fat Distortion in order to modify my DOD Grunge, and within 24 hours they helped.

The simplest solutions are the best.

Schematic of LFO section:



LFO goes to 1 and 18 pins of the first LM13600 and 1 pin of the second LM13600. DROP goes to 18 pin of second one.
Soon I will send phase stages.

You have this pedal in your hands ?

glad to see it being traced !

Thanks!

Its a nice pedal - lots of action for low £...

Here is FX22 genuine schematic

Really nice !! thanks !!

Hello there !
May I use this thread to expose my issue ?
Just received my 2nd FX22 ... Yes iI do love those pedal for Rhodes and electric keyboards ...
I've modified the 1st one in order to activate the speed (rpm's) with a volume pedal ... it works really nice!

Now on the second one the rpm's when at max is not fast as my first one (75%) ...
what could do this ? the pot seems fine as when I bypass it it is the same.
The IC (JRC 2904D) ?

Thanks very much
G

Hard to tell unless you explain a little more about how you modified your FX22's.
But no. It's not the IC. Why do you even think that?

Thanks fior answering !
No my modified one works perfectly independantly of the mod.
The problem is the new one on wich the speed doesn't go as fast as on my first one.
By reading the diagram kindly post by DoctorSound I can 't really see what could be the culprit ...
RPMS controls the speed .... DROP the depth.

Received that from DOD :
It might be that the taper of the pot is off spec, even if it reads the resistance values correct on a meter.
Regards,
Bill Clayton
Technical Customer Service
Harman Signal Processing

Seems to me a strange answer as when I hardwired bypassed the pot it doesn't change anything to the problem.

sikheazdraf wrote:

borislavgajic wrote:can you post some pictures of copper side ...

thanks

boris

here they are..
[ Image ]
[ Image ]
[ Image ]

Please man more PHOTOS of the solder side!! and the parts side please!!!

Did anybody make a pcb or veroboard layout for this one?

trubac wrote:Thanks fior answering !
No my modified one works perfectly independantly of the mod.
The problem is the new one on wich the speed doesn't go as fast as on my first one.
By reading the diagram kindly post by DoctorSound I can 't really see what could be the culprit ...
RPMS controls the speed .... DROP the depth.
[ Image ]

What nonsense from DOD!! It's the tolerance of C25 - most electrolytic capacitors have a wide tolerance - often as much as 20%! Your 4µ7 could be as low as 3µ7 or as high as 5µ6. If it's higher in value, the oscillator will run more slowly....

I've just managed to shunt the bypass network on my FX22.

It was a frustrating attempt at first, but after studying the schematics, I remembered something from my studies of passive crossovers in speaker networks, which was;
when you need a non polarized capacitor and you have none, wire up the negatives of two half value capacitors together, et voila, a non polarized cap is made.

In studying the schematic, I learned C12 & C13 on the input side of the effect block of the circuit, and C11 & C19 on the output side of the effect block of the circuit
are wired in such a way, with a J201 in between the capacitor pairs. The Source of each J201 are tied to an RC network to ground, Q2 & Q6 in between the capacitor pairs, and Q3 in the bypass loop. The switch button inverts which J201 Source to ground when activating the 4007A inverter IC network.


The Effect bypass bypass (or "always on") was accomplished by desoldering the negative side of C12 & C13, lifting it from the PCB and jumpering them with a length of wire.
For the output side I did the same thing to C11 & C19.


The Input & Output remain as originally wired and the TRS input functions to activate the battery snap B+ just as before.

The switch still functions to change the inverter (4007A) as before, but with the bypass shunt in place, merely deactivates/activates the indicator LED, having no audible effect on the sound output.

Your FX22 will now be ready to wire in your favorite True Bypass method: 3PDT, OptoCoupler, or Relay.

As soon as I have an idea about a better input and output circuit than the stock J201 input and 2N5088 output devices, I will post my findings.

(I just wish this pedal was still under warranty so I could add one more to the burn pile)

B_Y_O_Bass wrote:I've just managed to shunt the bypass network on my FX22.

It was a frustrating attempt at first, but after studying the schematics, I remembered something from my studies of passive crossovers in speaker networks, which was;
when you need a non polarized capacitor and you have none, wire up the negatives of two half value capacitors together, et voila, a non polarized cap is made.

In studying the schematic, I learned C12 & C13 on the input side of the effect block of the circuit, and C11 & C19 on the output side of the effect block of the circuit
are wired in such a way, with a J201 in between the capacitor pairs. The Source of each J201 are tied to an RC network to ground, Q2 & Q6 in between the capacitor pairs, and Q3 in the bypass loop. The switch button inverts which J201 Source to ground when activating the 4007A inverter IC network.


The Effect bypass bypass (or "always on") was accomplished by desoldering the negative side of C12 & C13, lifting it from the PCB and jumpering them with a length of wire.
For the output side I did the same thing to C11 & C19.


The Input & Output remain as originally wired and the TRS input functions to activate the battery snap B+ just as before.

The switch still functions to change the inverter (4007A) as before, but with the bypass shunt in place, merely deactivates/activates the indicator LED, having no audible effect on the sound output.

Your FX22 will now be ready to wire in your favorite True Bypass method: 3PDT, OptoCoupler, or Relay.

As soon as I have an idea about a better input and output circuit than the stock J201 input and 2N5088 output devices, I will post my findings.

(I just wish this pedal was still under warranty so I could add one more to the burn pile)

Thats awesome! I've got a vibrothang incoming so I may try that! Anybody know how to hook up a flashing rate led?

B_Y_O_Bass wrote:when you need a non polarized capacitor and you have none, wire up the negatives of two half value capacitors together, et voila, a non polarized cap is made.

Slight correction, you need 2 capacitors of twice the value you require not half.

viewtopic.php?f=7&t=20594&start=20#p257508

287m wrote:

Blitz Krieg wrote:^^^^ 2 uf?

no, two 1 uF polarized (+-) wired in series like +--+ , still 1uF

grrrunge wrote:

287m wrote:hey Miles
You can make a quick and dirty 1u nonpolar wannabe capacitor by tying together the negatives of 2 1u electro
then solder positive leg to board

No! Capacitances in series adds up like resistances do in parallel. 2*1µF in series would effectively give you 0.5µF.
To get 1µF you'll need two 2µF caps in series

normally, you right.
normal elco actually conduct in the reverse direction, two 1uF polarized act like they each have a diode in parallel with them that conducts when the voltage is backwards for that one cap.