frobnicator tremolo/ring mod debug

[awitee]

hi i just built the frobnicator from john hollis' site
http://www.hollis.co.uk/john/frobnicator.jpg
whenever i switch it to ring mod mode, theres a sort of high ptched noise, i tired adjusting the trimpot, but it doesnt help.. it reduces it slightly but it is still loud
and also the led connected to d1, does nothing, i was assuming that it was the speed led indicator, but it does nothing, i tried switching the polarity, still nothing
the tremolo sound works great, but no led blinking

[awitee]

forgot to mention that the 2 diodes on the board are blinking, only the one not on the board is not, ics used are 4558 at ca3080
edit*
i tried the r11 to 4.7k and r6 to 1m mod, and the ring mod noise is now quite managebale although when i max the freq knob it become a whistle
the 3rd led is now blinking (barely) its not that noticeable even in a dark area
any ideas how to make the 3rd led brigther? im thing it has something to do with the current from the 3080 pin 5

[col]

Arrghh! I wish I'd checked through these threads before building mine. I spent 3 hours trying to debug it yesterday and couldn't get on the computer 'cos my partner was on and she doesn't see sorting circuits out as high priority.
Basically changes I made were;
the substitution of R6 (10M) with 1M,
the replacement of R11 (10k) with a 47k trim pot, not the 20k that has been suggested most times,
addition of a 47n cap across the BC terminals of the transistor

using these changes I was able to get a good tremelo effect, the ring mod type effect needs further adjustment of the 100k trimpot and the additional 47k trimpot, I don't seem to be able to get a setting suitable for both.
There is still a slight ticking but this is not audible at playing levels, only when there is no signal from the guitar.

Hope this helps someone,

Col

[awitee]

still not able to fix the 3rd led's lack of brightness... anyone?
its starting to collect dust, ill probably still use it in the future without the 3rd led....

[col]

Awitee,

The third LED is much duller than the other two and should pulse noticably when on the tremelo setting.
The other two LEDs in series (or three - see other threads) are acting as a zener controlling the voltage and will glow brightly continuously. Until I'd sorted mine out with the 47k trim pot instead of a third LED in series the third one could barely be seen pulsing similar to yours. Now it is great as a visual aid to what is happening. On the RM setting this LED seems to glow continuously due to the high frequency of the modulation but it is still nowhere near as bright as the other two.
I would recommend the trimmer and see what difference it makes as simply adding more diodes in series gives voltage jumps rather than the fine control you can achieve with a trimmer and it is very sensitive.
There are a lot of posts on this circuit and most are very helpful and have useful information.

Hope this helps,

Col

[awitee]

where do i add the trimmer? diode>diode>trimmer>grnd or trimmer>diode>diode>ground?

[col]

You replace R11 (I think) 10k with the trimmer and adjust. Most threads have said that it can be a 20k but that wasn't big enough and I had to use a 47k. I just cut the resistor body out and soldered two lugs of the trim pot to them, then bent it over to lie on top of one of the ICs. It was then easy to adjust while playing for the best results,

Col

[crystal]

The problem with this circuit is that the oscillator wont oscillate with a full battery (9V). A 1n4848 in series with the positive side of the battery will cause a voltage drop of 0.6 Volts, making the oscillator work again. This circuit will continue to operate down to 6 volts, but at this point your headroom will be bad enough to make you want to change batteries.