Spin Semiconductor

HI all
I've build a e-guitar effect based on the FV-1. the project is the tonepad fraverb, which has been mentioned before in this forum.
I've already added the right regulator and components missing in the layout, so the unit is in perfect working order.

The effect worked really well for some time (several hours), now i got 20-30 seconds of perfect operation when i boot the effect, and after that i got a white noise that grows and becomes overwhelming in about 1 minute or so.
The noise is mostly evident with reverbs, more subtle but still present with pitch shifters.

Unplugging the power supply (i use only very clean power supply) and waiting approx 1 minute solves the problem for another 20-30 seconds

I may have damaged the fv-1 chip while debugging the unit when i was adding a simple dry/wet blender (which is not the source of the noise, when panned all the way to dry i got a perfect clean signal).

Any ideas?
thx a lot for every help.

Can you post a schematic with your mods? It sounds like there is a feedback path allowing the noise to increase over time. Does the time it takes the noise to increase change as a function of the wet/dry mix POT position?

the blender is not my design, but it is ultra-verified and you can see it there: http://runoffgroove.com/splitter-blend.html
The rest of the design is unmodded, just corrections in the layout and the 15pf added to the crystal.

i used this design several other times... it is wired in the most basic possible way: one send/return goes to the in/out of the FV-1 unit and the other is bridged for the clean signal.

the time does not change as a function of the POT position. Actually, it does not seem to follow any pattern: a few days ago the pedal worked flawlessly for 30 minutes.... then it may start the noise immediately or, most of the times, after 20-30 seconds.

I've had intermittent noise issues that we're due to bad soldering on some of the FV1's pins. Might be worth checking or reflowing your soldering.

OK, that schematic looks fine. I would next follow slackers recommendation and check all the soldering and for shorts, someone once had a short under the FV-1. Also, did you use flux when soldering?

first : thx a lot for your assistance

second: the connections are good, i've already verified them with a tester.

i don't have any shorts, or so it seemed. i'll recheck that tho.

for the flux, i used my usual soldering wire, with internal flux. Is that bad?

The normal solder with rosin core should have been fine. Some people have tried the water soluble fluxes and those are bad, they leave a conductive residue and cause shorts.

I'm running out of ideas at this point, and the fact it takes so long and is also intermittent makes me think it is something on the board other than the FV-1.

Just some thoughts to try:

If you remove the blend circuit is the noise still there?

Do you have an oscilloscope? If so can you monitor the input pin to the FV-1 and see if the rising noise appears on it, also check the output pin.

If the noise appears on the input pin to the FV-1 it means it is being generated by something else, backtrack the path to see if you can isolate it.

1)I don't really have to remove the blend circuit: the unit is stereo, so i just plug the signal in the channel 2 (which is not blended) and the noise is there.
No noise in the full dry pot position of the first channel.

2)i've already checked that and the noise appears at the output (both of them) of the fv-1.

Also, today while checking and trying to debug this thing i noticed that now it behaves differently: the noise comes and goes intermittently without any pattern (moving pots, signal /no signal don't seem to affect the noise)... until it stay at its maximum volume after a while.

I really think the unit is damaged. I build it, tested for like 2 hours and then closed into a (very) tight enclosure. There is any possibility that i shorted some pins or stuff damaging the fv-1 while mounting and closing the metal box? i know i did it with the effect powered on (a very bad habit of mine...)

Thx a lot frank, i'll order another chip anyway, i really like the way it sounds.


p.s. can i order the pre programmed chips from OCT to here in italy or do you have a dealer for my continent?

thx a lot

Europe is served by Profusion in England: http://www.profusionplc.com/

I tried to look at the file on tonepads site just to see if I missed anything to check but it gives me an error when I click to view the file.

Hi, i would like to know if this issue was solved. I have my circuit working for 2-3 minutes, then a strong white noise appears. I replaced the chip with another one and stills the same.