Univibe issue - bulb not bright / deep enough flashing.

[nznat]

Im having trouble with a vibe build. Here's the thing. When i plug in the power supply, i see the bulb go brighter and deeper in the flashing mode, seems perfect, yet after about 1 second after i plug in the power supply it suddenly goes more dim, the depth of the flashing has gone much dimmer / less, thus the lush univibe tone is mostly gone because of this, doesn't sound correct anymore. Any ideas on power supply issues on the pcb or what part of the univibe circuit controls the power of the bulb itself? Can anyone point to these areas and caps etc that regulate the bulbs depth of flashing on the schematic attached so i can remedy this situation?
much appreciate your help

 

[Big Monk]

I don’t see a schematic here. Maybe I missed it. I know the time I had a similar issue with a vibe sounding like a tremolo my Ldr had too large of a spread. And the dark resistance was too high. I solved this by running a resistor in parallel.

Or having an offset trimmer. Which this awesome design doesn’t have.

 

[Locrian99]

Yea I had to add an offset to my the depths from eqd clone because everytime id turn the rate low the lfo would stop o’n.

 

[Big Monk]

@nznat

We are just having a little fun with your predicament.

A few questions:

1.) Are you tuning the board with the light shield on?

2.) Which LDRs are you using?

3.) Can you tack in an offset control to the lamp driver circuit?

 

[nznat]

whats on second.

The guy who designed the board the OP says “sounds like shit”.

whos the OP?

 

[nznat]

I don’t see a schematic here. Maybe I missed it. I know the time I had a similar issue with a vibe sounding like a tremolo my Ldr had too large of a spread. And the dark resistance was too high. I solved this by running a resistor in parallel.

what rating on the resister?

 

[nznat]

@nznat

We are just having a little fun with your predicament.

A few questions:

1.) Are you tuning the board with the light shield on?

2.) Which LDRs are you using?

3.) Can you tack in an offset control to the lamp driver circuit?

Tuning with light shield on: YES
My LDR: PGM5659D
I installed an offset adjustment that replaced the 100k / 47k with a 250k pot.

 

[carlinb17]

17

 

[nznat]

17

17? resister value in parallel?

 

[Big Monk]

Tuning with light shield on: YES
My LDR: PGM5659D
I installed an offset adjustment that replaced the 100k / 47k with a 250k pot.

The light resistance in those LDRs is probably the culprit.

Data sheet says 150-300k when the generally accepted best sounding units have a range of 5-20k

 

[carlinb17]

17? resister value in parallel?

Sorry erroneous entry… must have been a bot

 

[fig]

GL5528 correct Derek?

 

[Big Monk]

GL5528 correct Derek?

Light resistance is a good range but Dark resistance is probably too low at 1M

 

[Locrian99]

I used the 5528 with a 330k (which if I remember right out it around 250k) in parallel in my the depths and am very happy with it. The part # for the abyss I believe has 500k which I’m sure would be fine.

 

[Locrian99]

This circuit may have some different needs though.

 

[nznat]

The light resistance in those LDRs is probably the culprit.

Data sheet says 150-300k when the generally accepted best sounding units have a range of 5-20k

can you show me the proper range. 5-10k doesnt make any sense. light or dark etc.? what is the part number for the best vibes? and what is the best vibe? Hendrix original vibe was dark as anything, the brightness didnt exist until he cranked the amp. these days people keep trying to create a vibe that sounds like a concert volume bright tone, yet in the bedroom, yet thats "nothing" like the real univibe which was NOT bright sounding at all, it was uniform and organic "big and round". everyone is going for the bright, because they are not going to be playing loud. check this out:

 

[Locrian99]

What we are referring to is the Ldr not the sound. So your Ldr when hit with a lot of light has a min resistance say 10-20k. When it’s dark it also has a resistance say 1M. Yours is have to look again when it’s light has like 200k and dark is 10m. That is why it sounds like a tremolo it’s not letting any signal through at 10m. I would try the gl5528 as was suggested it has good stats tayda has one similar stats that is around 500k dark I think. But in my albeit limited experience you want around 500k dark around 10-20k light. I’ve only built the one vibe that has 4 ldrs so the stats could be very different for yours.

 

[Big Monk]

I used the 5528 with a 330k (which if I remember right out it around 250k) in parallel in my the depths and am very happy with it. The part # for the abyss I believe has 500k which I’m sure would be fine.

My only concern with using this anecdote for the Univibe is that the bulb has different on/off and intensity characteristics as the LED in the Abyss.

 

[Locrian99]

I was literally editing as you posted. Yes it may be very different.

 

[nznat]

What we are referring to is the Ldr not the sound. So your Ldr when hit with a lot of light has a min resistance say 10-20k. When it’s dark it also has a resistance say 1M. Yours is have to look again when it’s light has like 200k and dark is 10m. That is why it sounds like a tremolo it’s not letting any signal through at 10m. I would try the gl5528 as was suggested it has good stats tayda has one similar stats that is around 500k dark I think. But in my albeit limited experience you want around 500k dark around 10-20k light. I’ve only built the one vibe that has 4 ldrs so the stats could be very different for yours.

great reply, thanks for that input. i have found a GL5528 that is local in my country. ill grab it and try.

 

[Big Monk]

can you show me the proper range. 5-10k doesnt make any sense. light or dark etc.? what is the part number for the best vibes? and what is the best vibe? Hendrix original vibe was dark as anything, the brightness didnt exist until he cranked the amp. these days people keep trying to create a vibe that sounds like a concert volume bright tone, yet in the bedroom, yet thats "nothing" like the real univibe which was NOT bright sounding at all, it was uniform and organic "big and round". everyone is going for the bright, because they are not going to be playing loud. check this out:

The best LDR I’ve used is the 9203.

5-20k Light Resistance.

20M Dark Resistance.