Help with LectricFX Star Chamber

[Maharg]

Hello folks,

Just got done a Star Chamber project to the point of calibration and have hit a few snags.  The wet signal seems much lower than the dry, and I'm not getting any effect (delay) whatsoever.  Hoping some of the geniuses on here can help me out... Voltages below to start - thanks in advance!

Edit: should mention; built with 2x XVIVE .MN3005
IC1
5.87
5.87
5.74
0
5.47
5.84
5.85
11.75

IC2
4.47
4.47
4.35
0
4.36
4.48
4.49
11.75

IC3
5.8
5.8
5.65
0
5.67
5.84
5.84
11.75

IC4
11.73
5.85
4.98
4.98
0
5.86
6.39
0.75

IC5
11.73
5.84
4.98
4.98
0
5.86
6.6
6.75 0.75

IC6
9.6
0.76
0.76
11.0
11.0
0.75
0
11.53
0.73
0.73
7.4
0.75
11.0
11.75

IC7
5.45
6.23
5.82
0
6.25
0
0
0
5.88
0
11.53
5.86
5.8
11.75

IC8
5.86
5.87
5.48
0
5.87
0
0
0
5.87
0
5.85
5.86
5.85
11.75

IC9
0.8
1.85
1.85
0
1.85
1.85
7
1.85
1.85
5.76
1.85
1.85
11.75
1.85
1.8
1.7

IC10
5.75
5.75
5.76
5.7
0.74
0.74
0
5.67
5.72
5.72
5.82
0.74
0.74
11.75

IC11
4.46
4.41
4.41
4.33
0.74
0.74
0
4.37
4.4
4.4
4.4
0.74
0.74
11.75

IC12
11.75
0
16.7

IC13
1.55
4.73
0
0
0
2.57
1.4
8.85

[Scruffie]

IC5 Pin 8, is that really the voltage you get?

Apart from that, I'm not keen on your IC6 voltages but I don't have the schematic in front of me.

[Maharg]

Good catch on IC5; typo on my part - corrected in OP.

[Maharg]

Any chance anyone here has tackled this one and wouldn't mind posting voltages?  I did try swapping some chips and a thorough visual inspection; can't seem to source the issue though I do not have a spare 4069 on hand.

Thanks in advavnce

[Scruffie]

https://www.madbeanpedals.com/forum/index.php?topic=33146.msg319109#msg319109

In Gordo's case in this thread it was a bad CMOS chip.

I would suggest audio probing too, are you able to follow the signal path?

[Maharg]

Oh thank you for the link, Scruffie - I did try to search but came up empty (even more broadly on the Googles for other builders).  Maybe it's "Chamber" vs "Chambre" ...

I have access to a meter, scope, probe, etc.  I will read up on that thread, and get to some more tinkering this evening. I'll surely report back.

[Scruffie]

Oh, well if you have a scope, you should be able to check the oscillator is working at IC6 pin 8 and that the PWM output is good at pin 6.

If both are good and the divided clock at IC8 pin 12 & 13 is good, you'll know the issue is in the audio path at least.

[Maharg]

Admittedly, I'm no scope-pro, but I've snapped a few pictures of the readouts in case you have a few minutes to check these out:

IC6 Pin 8:
https://drive.google.com/file/d/1trYkMLhMFtIjZ1ImxDM0DDCXqAzGoZH2/view?usp=sharing

IC6 Pin 6:
https://drive.google.com/file/d/1tmL77P5s7znyKlmEZgMxy7_5RJcpjcN-/view?usp=sharing

IC8 Pin 12:
https://drive.google.com/file/d/1tmG8xzJjUohIYPzF65qfQBnhZIhrgNzQ/view?usp=sharing

IC8 Pin 13:
https://drive.google.com/file/d/1tjE8A7thI46m6kDJEiOLiv6kErO8l5qw/view?usp=sharing

It looks to me as though maybe the IC6 readings are a bit muddy/dirty?  Clock looks good, though, I reckon...

[Scruffie]

Yeah, clock looks good, PWM output is a little tricky to see, but I think it's okay.

So can you audio probe in this sequence;

IC9 pin 10, IC3 pin 7, IC3 pin 1, TP-2, TP-3, Q3 emitter, IC2 pin 1, IC2 pin 7, TP5.

Let me know where you lose signal there.

[Maharg]

Thanks, Scruffie.

Hooking a frequency generator to the input, and probing the various spots you listed, all is good and strong until IC2 pin 1 - there is a slight decrease in amplitude, and then a further decrease at pin 7, and again a further decrease at TP5.  I don't ever lose signal entirely, it just gets progressively weaker across those three points.  This was with all controls on the pedal at maximum. 

[Scruffie]

Okay, well, just a quick and dirty test, swap around IC10 & 11 and then see if the signal loss moves to IC3.

If so, probably a good idea to replace the (now) IC10 4016 chip.

[Maharg]

Swapped IC10 and IC11 and indeed the signal loss did move to IC3.

I don't have any spare 4016's available, but can get my hands on a couple of 4066's.  I'll try one/both of those for troubleshooting and then report back...

[Scruffie]

Okay, while I think 4066 should work to test, I do recall reading that they don't quite work the same in a switched resistor set ups so you'll eventually want to exchange them.

Fingers crossed that'll resolve your issue.

[Maharg]

Life gets busy some times...

New 4016's on order, will report back.  Didn't want to be a dirty hit and runner - thanks for the help thus far, Scruff

[Maharg]

Hello again all - just wanted to loop back to report that I've been successful in getting this bad boy going.

It sat for nearly a year, then over the past week I tried swapping out my CDXXXX chips without success, then I built a better audio probe and noticed when biasing the second MN3005 in the calibration procedure that there was next to no output.  I replaced the second MN3005 (Xvive) with a new MN3005 (also Xvive) and I was in business.

I still feel that my voltages are a bit off based on others' builds, and I'll keep tweaking away, but as is now it's working and calibrated and sounds great.  Really great slapback sounds and nice medium length delay.  As the delay time gets longer, it gets quite dark (as expected) and it loves to self-oscillate! 

Anywho, just wanted to report back and especially thank Scruffie for his help on this one.

I'll put this one in the 'refine' pile, and now get started on the DC-Echo.... Cheers