Photon Vibe not vibing

[alexv38]

Hello there,

I assembled the Photon vibe and unfortunately I can't get any sound out of it when the effect is on. The lamp light isn't modulated either. So I am thinking I might have one issue on the signal path and another one in the LFO circuit. Just to mention it, I replaced the dual C100K (speed) with a B250K pot with330K resistors across (alternative proposed in these forums to avoid difficult sourcing of dual C100K).

Anyways, I summarized where I am at in the debug process with the shematic below, both sound probe and voltage checks. I believe I reached the extent of my debug capability and I kindly ask for further guidance . Any idea what to check next? Replace IC1 and IC3 in case of faulty ICs? How to debug the LFO?

Thank you for the help!

Alex

 

[Chuck D. Bones]

It is customary to post detailed photos of both sides of the board. 95% of the time, the problem is workmanship. Inspect both sides of the board under magnification. Looks for bad solder joints, incorrect components, shorts, etc.

Did you sub any parts besides the dual pot?

The 18V rail is low.

Oscillator not running. Q2-E is way too low. Verify polarity on C7 - C9.

Measure & report the voltages on pins 1 & 7 of all opamps.

 

[alexv38]

Thank you for the feedback!

I didn't change any parts except for the C100K dual

I inspected the board and indeed I had one short between R9 and LDR1--> corrected it but the overall behaviour is not improved. HV rail still at 15.8V and lamp is not oscillating. Maybe this short damaged a component (IC1?)

I confirm C7 and C9 are correctly polarized and I checked the voltages on the ICs:
IC1.1=7.1V; IC1.7=1.3V
IC2.1=12.25V; IC2.7=2.22V
IC3.1=7.24V; IC3.7=12.45V
IC4.1=4.32V; IC4.7=6.9V

I also joined the circuit pictures.

 

[Chuck D. Bones]

IC4 is not an opamp, we'll ignore those measurements.
All of the other voltages reported should be around 7.5V, most are not. A short between R9 and LDR1 would not hurt anything.

That is a very tight board. It's hard enough to assemble when you have the correct size components. Cramming oversized parts onto a board is a
recipe for failure.

330K in parallel with 250K does not give you 100K. The LFO might stall at the lowest speed. 180K is the correct value to parallel with 250K. Leave that as-is for now, let's get everything else corrected first.

There are at least two things wrong on your board:
1. The LFO is not running.
2. The opamp biasing is way off.

When #1 is fixed you'll see the bulb flashing.
When #2 is fixed, sound will get thru.

You should know that the vibing won't work right if there is stray light hitting the LDRs. Once #1 & #2 are fixed, you'll need to test it in a dark room before putting the board back in the box.

You need to trim the leads, clean the board and inspect everything under magnification. Check for incorrect component values (we can't read 'em in the pix). Look for bad solder joints, solder splashes, etc. You found one short so far, there may well be more.