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Hi all,
I’ve finished building (well almost…) the Dr Phybes with the wilkie mod as per picture, but am having trouble when switched to 90. 45 works fine – no noise, speed works fine, sounds great. But when I switch to 90 I get a slightly distorted much quieter signal. If I strum hard then I get a sudden volume increase to the correct volume then it quietens down.
I’ve been testing the circuit with an audio probe:
- similar level signal on the middle pins of the DPDT 45/90 switch in both positions (slightly different sound)
- similar sounding signal after R18, so that side of the circuit appears to be ok
- the difference is clearly heard on the output of Q5/R19 – quiet and slightly distorted with 90 and clean sounding and much louder on 45
Happy to post IC voltages if you think that helps. Guitar PCB supplied matched transitors. I’m not an expert – I’ve build 3 pedals – a homemade one many years ago from a circuit diagram (before I discovered guitar pcb), a mayo which works fine and now this, so any assistance would be appreciated (otherwise I have a very nice 45 phase pedal…).
Cheers,
Tom
We’d need clearer pictures of the mod wiring it’s very difficult to see, the brown wire going to R10 does look a little frayed
The part of the circuit where you describe the problem occurs is the mixing stage
If it happens when switched to phase 90 mode only then I’d check firstly the correct value resistor is being used and that you have good solder connections especially around R17 and R10 to the switch lugs 3 and 4, by what you describe it sounds like Q5 could be mis biasing giving you the distortion and volume changes
R10 is switched out in 45 mode, continuity check your switch lugs in phase 90 position, I’d reflow all the joints on the mod if you haven’t already
With the circuit working correctly aside from when it’s switched to phase 90 mode I’d guess your problem lies there with either a wrong value R10 or a poor solder joint
+1 Billy. Usually when I get an intermittent signal that pops in, it turns out to be a cold solder joint.
Hi Billy and Wilkie,
Thanks for your help. I pulled out both resistors and checked the values and ok. I reflowed all joints as well. Unfortunately still the same. I rechecked using the audio probe and still sounds the same.
When switched in 90 mode, I get good signal (listening to audio probe) on dpdt 2, 3, 4, 5, and therefore sounds good on the input to R17. But on the output of R17 it’s quiet. I’ve also taken some better photos and measured IC2 and Q5. Q5 is also a 2n3906 – not sure if this could be an issue. Anyway – appreciate the help and if you’ve got any ideas or measurements I should be checking I will keep on going!!
The pictures appear to show that R17 is completely removed from the circuit board. The mod instructions explain that only one leg of R17 is lifted and a switch wire is attached to it. Review the mod instructions. I believe you have wired it incorrectly.
Q5 seems to be just fine.
Thanks. One end of R17 is soldered into the board at the top R17 connection. Then the blue wire goes to the switch and the yellow wire goes back into the other socket for R17. Let me know if this is ok – I thought it was as per the Wilkie mod. I’m assuming the resistor values don’t change from the material list as I also note the drawing has the same banding on the resistors – but assuming this is for representation only.
I might disconnect and test the clean signal, and then do the reverse with the signal coming through IC2 to see if the the independent signal paths sound ok but then create issues when mixed together at Q5. Seems odd that using the audio probe I’ve got a good sound before R17 and then also before R18, but then when mixed together before Q5 it drops – like the two paths are interfering and partially cancelling out.
Will also run it from a power supply to make sure that the 8v isn’t creating issues.
Thanks for the help so far.
I believe I hear you say that you have a good phasing signal at lugs 2,3,4 and 5 of the DPDT switch in the 90 position. You should also have a good “dry” (clean) signal at the lower pad of R18 that connects to pin 6 of IC1. If so, the mixed signal should appear at the Base of Q5 and at R19. If you are losing the signal there, check for a cold solder joint in that area or near Q5. Another possibility may be a short to ground in that area or beyond Q5. Remove power and use your continuity test on a DMM to look for a short to ground.
One final problem I fear may be a faulty Q5. SInce you did not use sockets for the transistors, you may have damaged Q5 with heat. But, let’s look for these other possibilities first.
Your solder joint attaching R17 to the blue wire does look dry with too much solder on it I’d remove some of that excess solder and reflow there and where the wire attaches to the switch
Hold it together with a small alligator clip and run solder along the resistor leg and the wire and make sure it flows nicely, as Wilkie says unless Q5 is damaged its got to be a cold solder joint making a bad connection
Slightly confusing because 45 mode works taking out the last 2 phase stages from your description and R17 would still be in circuit in both positions as would Q5 so if it works in 1 position but not the other that would indicate they’re OK
The 3906 wouldn’t make a difference here the length of time you applied heat whilst soldering it in would 3 to 4 seconds is generally accepted as the safe limit
You’re definitely doing it right but even when a solder joint looks nice and shiny if there’s too much solder or it’s ball like it can be dry inside hence me saying make sure it flows nicely
Thanks again. Checked and no ground circuits around the correct sides of R20. Perfect sound with audio probe at pin 6 of IC1. I also tugged all the wires to see if I could get disconnection and no go. If I strum hard then the higher level signal kicks in whatever’s not working and it works. Then a second later as the strum dies down there’s a step change down.
I’ve pulled out Q5 and will pick a new one up from Jaycar this afternoon and socket it to eliminate this.
On the 45 setting the pedal is perfectly usable as a phaser, sounds great with no noise. Just odd it’s a no go on 90! For another $2 might get another TL074 as well – I’m assuming you couldn’t have a partially faulty IC?
If you are getting a good signal at IC2A pin 1, then the TL074 and its circuitry are all fine. You did reflow all joints from R17/R18 through Q5 and beyond? And you did reflow the R17 resistor connection to the wire to the DPDT switch?
And that’s a wrap folks, all working thanks!!
Replaced Q5 and instantly got a good sound, no distortion, but this time it was more intermittent and sounded like a wiring issue rather than the previous sound which worked with a solid strum but then died off. Wiggled the hell out of all the wires, and the brown wire on the top of R10 proved to be the weakest link, and eventually broke off. Recut and resoldered wires on to R10 and R17 and perfect. Suspect it was a combination of the transistor and connection to R10. Might need to work on my layout / wiring, as the build photos on the forum look a whole lot neater than my efforts.
One minor issue when plugged into power supply instead of battery but now fixed and all working. Not a massive difference in 45 compared to 90 sound, but definitely prefer the 90.
Now my only problem is to re-order my pedal board. I’m thinking it should go after the distortion pedals (that’s a mayo there), but before the delay.
Glad to see this all worked out.
I think pedal placement will also yield differences in how prominent the effect is including the mod. I prefer the phaser before distortion always but that is only my subjective preference. The Phase 45 is a much more subtle phase which is great for clean parts like Pink Floyd and the Phase 90 is more upfront like a Van Halen. To me both effects are more subtle pre-distortion and more up front post so the switch may come in handy depending on where you like it in the chain. The delay should always be last IMHO save Reverb being my only exception.
Most importantly enjoy!
Hooray! You have success! Congratulations!
I agree with Barry that the pedal order will provide different results. You may wish to try using the Order Switching board to make this a quick change.
I think you will have better success with your next pedal build. You ARE going to build another one, aren’t you?
Yes, now that I’ve got heaps of resistors, leds, 9v jacks and a proper alligator clip magnifying glass pcb holder thing it would be a waste not to use them!!!
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