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Hello,
I’m not a experienced Pedal-Builder this is like my 6th build or so, but I tried a Dr. Phybes build with the 45/90 mod. I finished the build and at first glance everything was fine. No weird noices or other stuff, LED-Working and I got the guitar signal if the pedal is on or off. My problem here is that it just doesn’t generate the effect this build is aiming for. I can hear that the Tone is changing slightly when I turn it on or turning the switches on or off. But it is still a pretty clear signal with no phasing or anything regardless of all switch/poti-positions. First I noticed is that the potentiometer isn’t affecting the sound at all, I tested it with a multimeter and it should be connected correctling (according to the instructions). Did somebody has any tips or anything ? I don’t really understand why the sound isn’t working like it should.
P.S.: Tested with usual 9V power supply and with my Harley Benton ISO Power supply.
Thanks in advance for any help !
Hi Mario
Welcome to the forum
Could you post some nice clear images of both sides of the pcb and offboard wiring to the DC jack, in and out jacks and 3PDT switch so that we can trace it and check component value and orientation
One of the most common mistakes is not installing the ground wire top left of the pcb labelled G
Hello Billy,
first thank you for the fast response. I tried to take two pictures in slightly different angles so you can see everything. As you see unfortunately i can’t take a picture of the pcb backside because of my wiring (i know it’s a little bit messed up, the build challanged me).
Explanation about wiring: both grounds are connected to the switch-board and this is connected to the jacks, so I guess this should not be the problem. The potentiometer is connected via the green and two yellow cables (green = left, first yellow = middle, second yellow = right lug of the poti). The other green and yellow cables are for the 45/90 mod and are connected with the switch. One problem I have is that i don’t really know if the in and outs are connected correctly, it’s not shown in the instructions with a PTD-PCB.
Again thanks in advance !
Did you adjust the trimmer
Post all your IC and transistor pin voltages
IC pin numbers like this pin 1 left of the dot / notch down one side and up the other side in a U shape
Yeah I adjusted it but it seems like it doesn’t affect the sound as well, at least I didn’t hear a major difference between min and max of the trimmer.
Okay I will try to do that, just to get it clear I hold on Pin 1 the black pen and on Pin 2 the red one 1-3, 1-4 and so on ? Does the pedal need to be switched on when I measure it ? sorry for these basic questions, but I didn’t need the multimeter till today. :/
No – with the DMM set to “DC Voltage”, the black pen goes to ground, then the red pen goes to #1, #2, and so on.
Also, adjusting the trimmer is best done in very tiny increments. I usually start with the trimpot set at “noon’ and tweak ever so slightly in one direction first. If the first direction of tiny incremental moves on the trimpot doesn’t work, I start over at “noon” and go the other way in tiny increments.
Allright thanks for that advice, I will check that and measure the Voltage as soon as I can and write it down here. Really Helpful !
So first of all i tried to adjust the trimmer in very tiny increments but that didn’t solve the problem.There were minor differences I guess but not got the correct output. I measured every IC and the transistors, I paste the results below. I experienced some switching between different voltages and wrote that down too for beeing as precisly as I can. I named every IC and transistor like its written in the schematic.
Thanks again in advance for any help !
IC 1
Pin 1 – 0.13 V
Pin 2 – 4.96 V
Pin 3 – 3.35 V
Pin 4 – 0.00 V
Pin 5 – 0.00 V
Pin 6 – 9.04 V
Pin 7 – 4.96 V
Pin 8 – 0.13 VIC 2
Pin 1 – 4.96 V
Pin 2 – 4.96 V
Pin 3 – 4.85 V
Pin 4 – 9.03 V
Pin 5 – 0.33 V
Pin 6 – 4.96 V
Pin 7 – 4.96 V
Pin 8 – 4.96 V
Pin 9 – 4.96 V
Pin 10 – 4.85 V
Pin 11 – 0.00 V
Pin 12 – 4.85 V
Pin 13 – 4.96 V
Pin 14 – 4.96 VIC 3
Pin 1 – 0.00 – 0.26 V
Pin 2 – 3.5 increasing towards 4.9
Pin 3 – 3.23 V
Pin 4 – 0.00 V
Pin 5 – 0.00 V
Pin 6 – 8.8 V
Pin 7 – switching between 8.2 V and 1.3 V
Pin 8 – between 0.00 V and 0.15VQ1
Pin 1 (Drain) – 4.96V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 4.85VQ4
Pin 1 (Drain) – 4.96V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 4.85VQ2
Pin 1 (Drain) – 4.96V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 4.85VQ3
Pin 1 (Drain) – 4.96V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 4.85VQ5
Pin 1 (Emitter) – 4.96V
Pin 2 (Base) – 4.35V
Pin 3 (Collector) – 3.09V
Another thing to mention is I am using 2N5457 for Q1 – Q4. I got another matched set here that i could use but it has the same values as the set thats currently in there.
**EDIT checked the pinouts flip your transistors Q1 TO 4 around**
Some of your voltages are wrong the gate voltages should be just over 2v could be a problem with D1 or the trimmer or the transistor pinout
Check the 5457 pinout is the same first, it may simply be a case of flipping the transistors Q1 to 4
D1 left side doesn’t look to be soldered in correctly but voltage appears ok I can’t see the value of the trimmer which should be 250K the code written on it would be 254
I think you may have IC1 pins 6 and 7 mixed up, 7 is power 9v and 6 output pin which should be around the same as pin 3
Good news is your LFO IC3 appears to be working with the fluctuating voltages
The 2N5457 and 2N5952 devices do NOT have the same pinout! Look at the datasheets for them both and you’ll see that pinouts are reversed. As Billy points out, the 2N5457s are JFETs and the 2N5952s are N-Ch FETs. And, they MUST be matched. My guess is that when your matched set of 2N5952s come in, the unit will work as expected once they are in place and the trimpot set accordingly.
I checked the trim pot it’s like you said 250k ohm. But I double checked the voltages on IC1 Pin 6 and 7 it’s like I written above 9,04 V on Pin 6 and 4.96 V on Pin 7.
So you mean just flipping around Q1-Q4 should help ? I thought that a matched transistor set should have equal transistors so I don’t really get why this should help, would be very cool if you have a quick explenation for me. 🙂
Thanks !
Ok just for my understanding. I can’t use these transistors at all ? I bought this as a kit from musikding.de so I thought that this should work as it is sold as a kit. Or did I understand it incorrect and i have to switch the transistors around for get the 2N5457 to work ?
So I flipped all transistors around I did understand what you guys meant. Unfortunately it didn’t fix the problem. The sound is pretty much the same with little bit of boost but not the effect it should have. I measured the voltages on the transistors again and it did change as I understand in a good way. The new values are:
Q1
Pin 1 (Drain) – 4.85V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 1.58 – 1.76 VQ4
Pin 1 (Drain) – 4.85V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 1.52 – 1.76 VQ2
Pin 1 (Drain) – 4.85V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 1.58 – 1.76 VQ3
Pin 1 (Drain) – 4.85V
Pin 2 (Source) – 4.96V
Pin 3 (Gate) – 1.58 – 1.76 VBut I don’t really get why the sound didn’t changed at all, I tried the same process of adjusting the trimpot in tiny increments again.
Damn deleted the wrong one!
Try adjusting the trimmer until you get just over 2v on Q1 to 4 gate pins
I think your op amp pin numbers are wrong you read them pin 1 left of the notch or dot then down from top to bottom to pin 4 then up the other side bottom to top pins 5 to 8
I think you’ve went down both sides so your pin numbers 5,6,7,8 are actually 8,7,6,5 that would make sense
First of all yeah you are right, I messed that up, sorry for that I measured both rows top to bottom :/.
Okay I will adjust it to get the right voltages hope this will solve the issue.
ok guys I got it to work finally !
I adjusted the trimmer just as you said and now it works like an actuall dr. phybes :D. Learned a lot on this one with your help really appreciate your effort in helping me out on this one.
Have a great day/night, once again thanks a lot ! 🙂
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