Photon Vibe - No LFO

[Briks]

My issue is that while the lamp lights up and the tone section affects the signal, the speed and depth knobs do nothing. I can move my hand across the lamp and get some vibe, but can't do it on its own. Should mention that when I first built it, I left out the L78L15 voltage regulator and powered it on, but I replaced the Max1044 IC once I realized my mistake and got the L78L15 situated.

 

[Nostradoomus]

Are you testing it in complete darkness?

 

[Briks]

Are you testing it in complete darkness?

Just tried it with the lights off and an enclosure covering it, no difference. Even not in complete darkness, wouldn't you be able to see the lamp pulsating at different speeds? This is my first univibe-type build, so excuse the ignorance!

 

[zgrav]

so your lamp is lit, but not pulsing? do adjusting the trimmers make any difference in the brightness of the lamp?

 

[Briks]

so your lamp is lit, but not pulsing? do adjusting the trimmers make any difference in the brightness of the lamp?

That's correct, it's lit and not pulsing. The trimmers do make a difference in the lamp brightness.

 

[Robert]

Make absolutely sure nothing has poked through your insulating tape behind the dual potentiometer....

This is almost always the cause for problems on these (and the Abyss).

 

[Briks]

Make absolutely sure nothing has poked through your insulating tape behind the dual potentiometer....

This is almost always the cause for problems on these (and the Abyss).

I added another piece of insulating tape and angled it off the board a little so there was absolutely nothing touching. Still no pulsing. The dual pot I got feels a little janky even though I got it from Small Bear. Wondering if I need to replace it.

 

[zgrav]

use your dmm to measure the lamp voltage when with your speed control turned down and see if you are getting any variation in the voltage. if you are, see if the rate changes when you adjust the speed control.

how much can you dim the lamp with the trimmer? all the way off? in general it seems like the best range for the lamp cycle is to go from nearly off to something brighter instead of a range that is from bright to really bright.

in general, you will be troubleshooting the section of the schematic that feeds the light and has the controls for the rate, depth and speed. check part values and look for any issues with cold solder joints or possible shorts.

 

[Briks]

Lamp voltages remained constant after turning the Speed pot. Going clockwise from top left, the voltages are: 6.53; 6.53; 16.02; 13.06.

I checked everything in the light region of the schematic. Only discrepancy was that I had a 2M resistor in instead of a 2.2M resistor. I changed that out but it didn't make a difference (kind of figured that'd be the case). I reflowed some of the joints but nothing looked particularly egregious.

Still no pulsing unfortunately. I may desolder the Speed pot, test it, and solder it back in unless there's something else I'm missing. Either way, I appreciate all the help thus far.

 

[zgrav]

you should be able to test the speed pot while installed, just test the resistance between the center lug and each outside lug as it is rotated, and check resistance between the outside lugs. when you are checking the parts for the lamp circuit are you also testing for continuity between the parts as laid out in the schematic? have you measured the voltages on the transistors?

 

[Briks]

im confused as to why there is a missing wire thats supposed to go to the switch

I typically leave that off for testing since the 9v is at the top of the pcb as well.

 

[music6000]

That's correct, it's lit and not pulsing. The trimmers do make a difference in the lamp brightness.

Is Trimmer 2 definately 500 ohm, Not 500k?

 

[Briks]

Yeah, trimmers all seem to be correct. I did end up changing out the Speed pot as I wasn’t getting any resistance on the lower tier. All I had was a b100k dual gang. Still no pulse and now not getting any audio through the pedal. I probed the whole audio path, which worked every step from input to output, but still nothing without the probe. May need to throw my hands up and take a few days off from this one.

 

[music6000]

Check for continuity on these matching colours
There is no connection to the Crosses:
.

 

[Briks]

Is Trimmer 2 definately 500 ohm, Not 500k?

Double checked with DMM, definitely 500r

 

[music6000]

Double checked with DMM, definitely 500r

Did you check for Continuity in Pic above to rule out Trace damage.

 

[jpalmer5948]

i have the same exact problem...have followed everything in this thread so far...nothing

 

[music6000]

Did you use Potentiometer Dust cover & Insulator under dual Potentiometer under Board?
if you just use Insulation tape, There is every chance pots are shorting out out on PCB.

 

[Chuck D. Bones]

Board needs to be very clean, no flux residue. Make sure C7-C9 and C14 are facing the right direction. You can check the LFO alone by doing this: Temporarily connect a superbright LED cathode to ground. Temporarily connect a 22K resistor from SPEED pot pin 2 (either pin 2, doesn't matter which) to LED anode. Set SPEED to the middle. Does the LED flicker? If it does, the LFO is running. The LED will flicker more brightly at high speed, and the flicker will be weak at the lowest speed, that's normal for this LFO.

I have a Photon Vibe mod in progress (almost done) and I can tell you that the LFO is very touchy. If C7-C9 are leaky or the wrong values, the LFO won't run.

jpalmer, you probably should have started a new thread since most of what's in here (like the pix and measurements) do not apply to your build. Post pix of your board, let us know if you subb'ed ANY parts.

 

[Chuck D. Bones]

Did you use Potentiometer Dust cover & Insulator under dual Potentiometer under Board?
if you just use Insulation tape, There is every chance pots are shorting out out on PCB.

RIGHT! Follow the advice in Basic Workflow Tips for Building a PedalPCB and space your pots off of the board.