Harmony Generator

[RickL]

I built the Harmony Generator found at Mark Hammer's site here:
http://ampage.org/hammer/files/EMMHarmoGen.PDF and I can't get the voltage transformer part to work. If you look at the schematic you'll see that a -6v supply is supposed to be derived from pin 7 of IC 8 after going through a couple of caps and two diodes. I get about -0.7 volts where it indicates -6v. The output of the pedal is a LOUD, pitched tone that can be varied somewhat with the selector switches.

If I force the -6v point to a greater negative voltage by connecting a battery across it I can get the effect to work (I guess... the tracking isn't very good but both switches have an effect, the gain control works and the balance pot works). A 9 volt battery only yields about -6 volts but this may be due to a less than new battery (it reads about 8.7 volts unloaded) or because I'm not disconnecting any of the circuitry when I connect the battery.

My question, after this long winded prelude, is can someone explain why the little circuit should give -6v and why I might not be getting -6v?  When I measure the diodes in the circuit I get about 0.6 volts forward drop and 1.8 volts reverse drop on both. Measuring a diode from the same batch gives an infinite reverse drop like I would expect. I originally used recycled parts for the diodes and caps but replacing the caps with new parts didn't make any difference.

If I have to I'll just get rid of the -6v circuit and use a second battery but it would be nice to have it working the way it's supposed to.

[RickL]

Well I got tired of waiting...   ... so I went ahead and disconnected the inverter circuit and added another battery. Everything works as it should, however...

The tracking on guitar is horrible. To be fair I don't think this was ever designed to be used with guitar, the text mentions synths and it does track quite well if I feed it a sine or square wave from a test oscillator. It's also loud. The gain has to be turned up some to get it to track which puts the output way above unity unless the balance control is barely towards the effect side. I solved that by adding a 100k volume pot at the output.

I tried various combinations of pickups and tone settings but nothing seemed to help the tracking much. Maybe I'll try feeding it with a square wave fuzz although I don't really expect much. Oh well, at least it'll be good for making weird, unpredictable noises. Think Blue Box on a really bad day.

I'd still like to get it to work on one battery if possible, or at least to know why the inverter circuit doesn't or won't work.