Distorting auto-wah that shouldn't

[Mark Hammer]

I finally got around to wiring and powering up this diode-ladder autowah from an old Japanese project book.  It requires a bipolar supply, so I wired up a 7662 charge pump to turn the 9v adaptor into a bipolar supply.   The thing whines like crazy (a problem I can fix by replacing the 7662 with a 1044 and connecting pins 1 and 8 for a higher clock frequency).

The problem is that it distorts, and doesn't seem to have much frequency tuning range.  Is the issue a current limitation, stemming from use of the 7662?  Because all the documentation is in Japanese, I can't tell if there are current requirements exceeding what a charge pump can provide.  Here's the circuit below.

Some of the test voltages seem close enough - off by a few tenths of a volt.  But others less so.  For instance, the schematic says that the voltage at the common emitter junction of that pair of 2SC1815s over on the upper right should be 4.3V.  I'm getting 5.4V.  The emitter of that 1815 feeding the top of the diode ladder should be 6.5V.  I'm getting 7.6V.

Any ideas?

[idiot savant]

For instance, the schematic says that the voltage at the common emitter junction of that pair of 2SC1815s over on the upper right should be 4.3V.  I'm getting 5.4V.  The emitter of that 1815 feeding the top of the diode ladder should be 6.5V.  I'm getting 7.6V.

Those are the problem areas.

7.6V looks good for the top transistor base voltage, the emitter should be lower than that by Vbe which looks like 1V-ish according to the datasheet.

At the same time that is messing with diff amp transistors. The bases of those need to be 3 diode drops lower than the upper transistors emitter, and then their emitters should be Vbe lower than their bases.

bad/shorted/backwards 2sc1815 on top of the ladder?