FIXED Recalcitrant Pork Barrel...

[blearyeyes]

IC3 (3101) my results look almost identical.
IC4 (3007) all except 7 and 8 (4V) which at my last reading were both 6.63V

Any ideas what could cause the difference?

I will compare IC1 and IC2 later today.

Forgot to add my readings taken with both pots max.

The pot settings usually.

[wilsona]

OK - so were your readings taken at max?

[blearyeyes]

no I could do it again.

[wilsona]

Just 7 and 8 of the 3007 IC4 would be useful.

[wilsona]

Regarding IC 1 and 2 my results are much the same although I am not getting as much variation on those pins with a varying voltage on IC2. e.g. Pin1 I get 3.5-6.0  while the range posted by blearyeyes is 1.8 - 8.0

I think I am going to go through what has been done and post a summary of what we have and see if it rings any bells. The fact that input to the 3007 has audio present but output ( 7 and 8 ) has nothing must mean that the issue is either between the chips or between the 3007 and further along the path to main output.

[RobA]

I don't know this for sure, but it feels like pins 7 & 8 need to sit close to the bias voltage. And that high a voltage seems to me that it would be too high to set the bias for other parts of the circuit. I'd check all the areas around the jumpers again and the connections for R20 and R20 itself. I'm not sure you can measure R20 in-circuit, but it might work.

I just had a thought, maybe the BBD's you have just bias high. Perhaps you can get to the bias point if you try to run the input power at 12V. I think it would be worth a try if you've got a 12VDC supply around.

[wilsona]

R20 one side relative to gnd measures 6.6V - same as 7/8 of 3007. I presume this is what to expect.
Across R20 measures 1.95V
The other side relative to gnd measures 8.7V

I don't really know what that means, tbh.

I redid the jumpers area and replaced the 3101 socket, reflowed all socket pins - unfortunately I do not know which pads to check that jumpers are connected properly.

I think I only have an 18V PSU around, I'll have a look.

[RobA]

You can see where the jumpers hook things to in the little inset. For the MN3007, the jumpers will make it so you have pin 5 going to ground and pin 1 and one side of R20 connected to pin 1 of the MN3101 (and the + supply voltage).

The one side of R20 and pins 7 & 8 should be at the same voltage, it just seems that 6.6V is pretty high, but I don't know what's in the normal workable range or if it is the BBD that is primarily responsible for setting that voltage level.

[wilsona]

Might need  comma in that sentence. I am reading it as -

"pin 5 going to ground, and pin 1 and one side of R20 connected to pin 1 of the MN3101"

I have:

One side of R20 is the same as 7 and 8 of 3007.
Pin 5 of 3007 -> gnd
Pin 1 of 3007 -> one side R20

I do not have one side R20 -> Pin 1 of 3101

[RobA]

Yeah, I could have said that better. Pin 5 should go to ground. The junction of Pin 1 on the MN3007 and R20 should be going to VD. Pin 1 of the MN3101 should also be going to VD. The inset diagram shows the jumper going to a trace and that trace continues on to Pin 1 of the MN3101, so you should have continuity from the junction of Pin 1 of the MN3007 and R20 (which coincides with the top jumper) and Pin 1 of the MN3101.

[wilsona]

Yeehah! Found it. At last. Thanks everyone for all of your help in narrowing it down and pointing me in the right direction. I have learned a great deal about debugging and to be honest, although tearing my hair at times out I have quite enjoyed the process.

Don't know whether it was a PCB fault or the result of my inexpert soldering and subsequent redoing of the jumpers, but the pad on the jumper indicated on (blurry) attachment was not making proper contact with the track. I bridged it with a little solder till I got consistent continuity between all points. Once assembled again readings on pins 7 and 8 were just under 4V as required.

Pedal is now working.  Does not like to be driven with a high input however. Distortion evident at a fairly low level. I'll try it before my compressor. Sounds great though, brings back a lot of memory associations. Ah, the 70's!

Thanks again for all of the help, I am am extremely grateful.

[RobA]

Ah, victory! Congrats, on getting it working. It can be frustrating and fun at the same time.

Now you have to come up with something to build for that extra MN3007 .

[wilsona]

Yes - I might look around for another chorus board that uses that combo. Got PCBs for trembulator, cupcake, runt, rangemaster and bloviator (?) to keep me busy - already built an Umble, Afterlife and an 'order flipper'. My pedal board is now too small! Would love to build a fully featured multi loop pedal management project, not seen anything that ambitious in the hobbyist realm yet.

[blearyeyes]

Feels good to finally find it!  Congratulations!

Add a Road Rage and run it at 15 volts, it is much cleaner. That's what I decided to do cleans it up much more headroom.  Also added the Tonepad cap mod. Better. Changed resistor 39? To 47k from 4k7.  Starting to remind me of my CE-2 that I never should have sold..

I think JMK has a pedal looper system that might be of interest.

http://jmkpcbs.com/product-category/epic-bypass-looper/

[wilsona]

I do have a spare road rage board, might have a go, although not much room left in my case.

I've just added the depth LED mod but not as good as I hoped - the LED flashes and gets more intense but the depth seems less. Will lookup the tonepad cap mod. Can hear the LFO ticking in background, need to look into shielding.... 

This Italian company do a kit: http://www.aresaudio.com/picolooper3.html

Thanks for your help - zeroing in on the output voltages got us there in the end.