Neutron voltages

[mdh]

I have a Neutron (http://www.geofex.com/PCB_layouts/Layouts/neutronpub.pdf) on my breadboard at the moment, and I haven't been able to get it quacking. Obviously since it's on a breadboard, I might have screwed up some connections, but I've been through it a bunch of times (admittedly, I found a couple problems on the last pass, but now I'm not finding any errors). I've been flogging this poor thing for about two weeks, so I figured I might as well see if the symptoms and voltages ring any bells (I've been through the archives, and though I've found similar problems, I haven't really come across solutions). Here goes.

For the optocouplers, I'm trying to use a couple of single LED/LDR optocouplers that I got from Electronic Goldmine (http://www.goldmine-elec-products.com/prodinfo.asp?number=G15396). They seem (on the face of it) to be similar to NSL32, CLM6000, etc., but I think they might be out of spec or something. They're marked NSL7053, which does not come up on the Silonex site, or even in Google. I measured the LDR resistance vs LED current for one of them, then discovered that the dark resistances vary all over the map. Out of a bag of 8, the dark resistances varied from 170k to > 2M. This does not inspire confidence, but I used a pair that seemed to match, with dark resistances of 220k. I haven't tested the resistances of this pair with the LEDs on. Rx is around 4k at the moment. I don't think the optocouplers are my only problem, though, because the voltages on U3 don't seem right, if I'm understanding past threads correctly.

Other substitutions: used (specified)
  gain pot is 1M linear (1M rev log)
  peak pot is 100k log (150k log)
  c1 is 4.7u aluminum electrolytic (tantalum)
  c6 and c8 are 3.2n (1.8n @ range low, 4n @ range high)

I'm using two 9V batteries, so no charge pump or AC supply to complicate things. And it's wired in band pass mode.

Symptoms:
  With direction switch in the up position, the effect is extremely subtle or absent. The peak control doesn't seem to have much effect on the sound.
  With direction switch in the down position, there is a lot of buzzy farting action going on. So, probably some envelope ripple getting through.

I think the filter portion of the circuit is fine, however, because if I replace the LDRs with a dual-gang 100k pot, I can sweep the filter by hand, though it doesn't sound very funky (perhaps a sub-optimal taper on the pot). What really is throwing me is that the voltages on the op-amp pins in the envelope follower seem way off, though I may be the one who's way off. In an earlier Neutron thread, R.G. suggested that the op-amp voltages should all be relatively close to 0, for all pins except the supply pins. Here's what I get:

+ve battery: 8.9 unloaded, 8.8 loaded
-ve battery: -8.8 unloaded, -8.7 loaded (should I be worried about ~100mV mismatch in battery voltages?)

The supply pins of U1, U2 and U3 are all at -8.7 (pin 4) and 8.8 (pin eight). [edit: (pin ... seriously]

Non-supply pins:

U1 (mV)
1  -1.9   
2  5.9   
3  1.6   
5  0       
6  1.6   
7  1.6   

U2 (mV)
1  13.9
2  1.5
3  0.5
5  0
6  -1.9
7  1.5

U3 (V), direction switch down
1  -7.32
2  3.68
3  3.47
5  0
6  -0.9 (changing toward 0V as long as the probe is in contact with the pin)
7  7.97

U3 (V), direction switch up
1  7.75
2  5.91
3  7.21
5  0
6  -8 mV (counting down as before)
7  7.96

Notice that the U1 and U2 non-supply pin voltages are all in mV, whereas U3 voltages are in V. If you've made it this far, thanks for reading! Any thoughts?