Neovibe. LFO fried

[Sinzu L.J]

Hi there. First post here. Looking for some light in the darkness

I build a GGG Neovibe and im having a lot of issues with the LFO.  This is the third time that burned in 3 months.

Im playing a lot since i build it, 4hs min. I read that its common that the lfo transistors die. But i think this isnt normal at all.

The last time i replaced the transistors. LFO worked again but now im not having audio signal. Weird, super weird.

I audioprobe the input stage. Signals dies in base of Q1 no signal at all in Q2, Q3. Then i replaced all  caps and transistors of the preamp section. Nothing changes.
Im going to replace resistors of the input stage and see what happens.

The burning LFO and the input stage maybe a sympthom of another issue ?

Im using a 24v power supply. DC Jack is isolated. But the in/out jack are not. In/out jack can be the cause of the constant burning ?

Its "normal" that LFO dies to often ?


I hope anyone can enlight me a little.

Thanks ! 

Lucas

 

[PRR]

No, they should not die.

Where are you getting parts?

Are you using the GGG kit or ??

WHY are you feeding 24V? That is significantly high. Is it a steady 24V or does it run higher at light load?

[Sinzu L.J]

Thanks for reply !

I get the parts in a local store and etched the board.
Its a little larger than the GGG board so i have a little more space between traces.

The doc says 18v to 24v power supply. I did not choose it for any special reason. I only had a 9v, 12v and 24v power supply in home. Just happened.
Its a " regulated" switching power supply not linear. Thats the only data i had. Its suspicious, i know.

[Sinzu L.J]

Well i replaced the entire input stage but nothing have changed... Odd situation i cant find the problem

[kaycee]

Randomly replacing sections isn't a good strategy.

Looking at the build doc, it states a 15 volt supply and gives voltages to check.

http://www.generalguitargadgets.com/pdf/univibeupdate.pdf

I've built several Univibes and only burnt out one driver bulb due to over volting via a short.

[Sinzu L.J]

Randomly replacing sections isn't a good strategy.

Looking at the build doc, it states a 15 volt supply and gives voltages to check.

http://www.generalguitargadgets.com/pdf/univibeupdate.pdf

I've built several Univibes and only burnt out one driver bulb due to over volting via a short.

Its states 15v supply in the schematic after that regulator. Input voltaje 18v to 24v dc.

The problem wasnt the driver transistor, bulb always worked. The LFO was the problem. I fixed that and its working. But like i said, its a sympthom of another problem that i cant find out.

I didnt replace the input section randomly. I did that because the audio signal dies in the input stage now. And that didnt happened before.

[Kevin Mitchell]

Voltages would help. Check the output of the 15v regulator.

I would investigate your 24v power supply. Perhaps that's blowing up your parts.

[Sinzu L.J]

Voltages would help. Check the output of the 15v regulator.

I would investigate your 24v power supply. Perhaps that's blowing up your parts.

Love u. I replaced the regulator and worked.  The bulb was glowing so i thought that everything was ok with the power section.

Conclusions:

I need a new power supply.
Lfo dont die too often.

Thank u so much.

[Kevin Mitchell]

My pleasure. And welcome to the forum!

As you probably now know the semiconductors in the signal path are powered by 15v from the regulator. Since the signal wasn't passing through the 1st semiconductor it only makes sense that the regulator had blown - especially because it was working before. Something had happened and from what you've explained here, will likely happen again if operated under the same conditions.

Moving forward I hope you check voltages before taking parts off! Even if it feels like a chore to find what parts have survived or not, it's worth learning how to tell.