DuoPhase LFO no LFOing

[Aentons]

All voltages look good but neither of the yellow LEDs are lit. All trimpots set at noon. All the TL072 came from Mouser. Signal is passed in bypass and effect. A weird thing I noticed when putting it together was the led negative pad was square rather than the positive but they are marked with A and K so I checked the schematic to verify and used the letters.

Any ideas what I should check?

 

[DailyDovetails]

I can’t tell what way they are on yours but on mine the flat/cathode side of the LED is towards the top/jacks.

Do you have the depth turned up? I think the trimmers affect the light some but I don’t recall it being a ton.

 

[Aentons]

My flat side is facing away from the top jacks. That's gotta be it then. I'll pull the LEDs and reverse them. Thanks

 

[jwin615]

Down the road, those LDRs may need to face the LEDs.

 

[mybud]

You are testing this in dark conditions, right? It's worth covering the LED/LDR assembly in black cloth or something similar if you're testing it in daylight.

 

[Aentons]

I can’t tell what way they are on yours but on mine the flat/cathode side of the LED is towards the top/jacks.

Do you have the depth turned up? I think the trimmers affect the light some but I don’t recall it being a ton.

Thanks. Reversing the LEDs made them light up. I guess the square negative pad threw me. I think I have some other issues also. One LED is inconstantly flickering and other is always on no matter the trim pot or switch settings. I'll try and reflow some spots.

 

[DailyDovetails]

Thanks. Reversing the LEDs made them light up. I guess the square negative pad threw me. I think I have some other issues also. One LED is inconstantly flickering and other is always on no matter the trim pot or switch settings. I'll try and reflow some spots.
View attachment 87875

Mine took a bit to get going right also. I initially had all the ICs in with the notch up and one of the charge pumps in the wrong spot. It’s a cool pedal once it’s going.

 

[Aentons]

Ok, I am still having issues on this one.

It's strange, I got other LED blinking by reflowing C19A. But the A side had no sound when not in bypass.

On the B side, the LED blinks and it passes sound when not in bypass but no phasing, even in dark room with my hand covering the LDRs.

I decided to just careefully reflow every joint. No change on the B side. The A side LED is not blinking anymore. I tried removing C19A and cleaning it up a bit but no change.

I replaced C17A and C18A since there is no negative voltage on IC7A pin5

I think I've checked all grounds between the negative power pin and everything checks out.

I switched out chips from A to B side and tried wiggling the chips and caps just to see if something happens. I even took out the sockets for IC5A and IC7A and direct soldered them.

I feel like I'm missing something obvious...

 

[Aentons]

Oh, I also noticed R38 and R46 locations are switched between sides. Is that correct?

 

[Aentons]

I think I found an issue

 

[Nostradoomus]

jumper it just to be safe

 

[Aentons]

jumper it just to be safe

A jumper did the trick for the LFO. Both LEDs are blinking now. Still no phasing on either side in a dim room with magazine laid on top. I guess I need to make the LDRs face closer to the LED? I didn't think it was going to be that sensitive based on some other folks comments.

 

[Nostradoomus]

it's been awhile since I made this or a phase II but I always have the LDRs standing up facing the LED. Consider the LED not shooting much light downward unless it's reflected properly, that's probably the issue.

 

[Aentons]

I forget who but in another thread there was a mention of it working if you lay them down like a flower pedal so I figured I'd try it.

Also, at the time I bought the LDRs there was a mention that the Tayda ones worked, and at that time they only had one type, so that's what I used. I've had this stuff laying around for a while. Should probably confirm these work.
Here is what I have. SKU A-1528

Photo Conductive Cell Resistor LDR 540nm RADIAL 5528

Tayda Electronics - Get It Fast - Same Day Shipping

www.taydaelectronics.com

 

[Nostradoomus]

have you tried it with the enclosure lid on it? might reflect a little better

 

[Erik S]

I forget who but in another thread there was a mention of it working if you lay them down like a flower pedal so I figured I'd try it.

Also, at the time I bought the LDRs there was a mention that the Tayda ones worked, and at that time they only had one type, so that's what I used. I've had this stuff laying around for a while. Should probably confirm these work.
Here is what I have. SKU A-1528

Photo Conductive Cell Resistor LDR 540nm RADIAL 5528

Tayda Electronics - Get It Fast - Same Day Shipping

www.taydaelectronics.com

I can confirm that the “flower petal” arrangement worked fine for me. And I was just copying from someone else’s build report. Pretty sure I used the ke10720 LDRs.

Here’s a post vouching for the 5528 in a phase2 which I believe is half of a Duophase.

J

Thread 'Phase 2 - LDR’s - Photoresistors'

Oct 20, 2024

Hello pedalpcb community,

I would greatly appreciate some insight.

I am building the Phase ii.

Phase II - PedalPCB.com

Compare to Mu-Tron Phasor II

www.pedalpcb.com

It calls for KE-10720 LDR Photoresitors and a Yellow LD. I ordered all the parts per specifications in the build document but tayda was out of KE-10720.

So i ordered Photo Conductive Cell Resistor LDR 540nm RADIAL 5528.

From other threads i have gathered that the important details are the photo resistance and dark resistance which are very similar (good, i think). I have compared the manufacturing specs on both.

PR 10k to 20k. DR 0.5...

• Jer
• Replies: 12
• Forum: Modifications

 

[Aentons]

I put it back in the enclosure. All knobs, switches, trim pots and LEDs seem to be working as intended. Fully enclosed and still not a hint of phasing on either side at any knob or trim setting. I tried holding the red pot condoms on with the enclosure back off and still nothing. All I hear is the clean sound and a little whine from one LFO and clicking from the other

 

[zgrav]

post a pic of the solder side of your PCB if you are still trying to get this to work.

 

[DGWVI]

Do you have any 1054s on hand?
I don't think the 7662 you have in there will deliver enough current

 

[Aentons]

post a pic of the solder side of your PCB if you are still trying to get this to work.

Ok, here is the other side.