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What would cause a Stage Fright to over drive?

Started by LaceSensor, May 10, 2014, 06:06:52 PM

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LaceSensor

I had this stage fright built months ago and Im sure at the time had a tech thread about it
was doing an inventory today and found the PCB

it still clips!
It phases, and the trim on board increases the depth of the phase, but in all aspects, it clips / overdrives

Ive changed out one by one all the socketed parts (ICs, lm13700s, transistors, FET), no dice
any ideas?
anyone got voltages?

RobA

I have these voltages written down for my StageFright in a doc I've got saved. I think they are right.

LM13700's will overdrive and distort if the current into any of their inputs is too high. Check the resistor values for the various bias inputs on the OTA's.

Voltage in: 9.4
IC1: (TL074)
1   4.67
2   4.67
3   4.25
4   9.33
5   4.64
6   4.65
7   4.65
8   4.67
9   4.64
10   4.55
11   0
12   4.62
13   4.65
14   4.64

IC2: (TL062)
1   Moving (.69 to 8.7)
2   4.65
3   2.8 to 6.5 or so
4   0
5   4.69
6   4.68
7   3 to 6 range
8   9.35

IC3: (NJM13700D)
1   1.16 to 1.27
2   0.291
3   4.57
4   4.57
5   5.72
6   0.31
7   5.6 to 5.78
8   4.58
9   4.59
10   5.64 to 5.7
11   9.16
12   5.63 to 5.73
13   4.58
14   4.58
15   0.38
16   1.13 to 1.27

IC4:
1   1.12 to 1.3
2   0.286
3   4.61
4   4.61
5   5.72
6   0.3
7   5.61 to 5.78
8   4.58
9   4.56
10   5.66
11   9.15
12   5.58 to 5.69
13   4.58
14   4.58
15   0.317
16   1.14 to 1.28

IC5:
1   1.11 to 1.3
2   0.29
3   4.63
4   4.61
5   5.64
6   0.4
7   5.68 to 5.75
8   4.58
9   4.60
10   5.75
11   9.23
12   5.60 to 5.76
13   4.62
14   4.61
15   0.363
16   1.14 to 1.28

Q1:  (2N3904)
E   3.90 to 3.98
B   4.56
C   9.14

Q2: (2N5457)
G   0
S   1.184
D   3.90 to 3.98

Q3: (2N3906)
E    4.56
B   3.90 to 3.98
C   1.13 to 1.38
Affiliations: Music Unfolding (musicunfolding.com), software based effects and Rock•it Frog (rock.it-frog.com), DIY effects (coming soon).

RobA

The main resistors I mean are R8, R13, R18, R23, R28, and R33, but the OTA can be sensitive to the input levels too so it could be something with R7, R12, R17, R22, R27, or R32 as well. The other place that works into it is the current/voltage coming out of the final stages of the LFO, so it could be something in the transistors at the output or maybe the filter and bias voltage components just after the TL062.
Affiliations: Music Unfolding (musicunfolding.com), software based effects and Rock•it Frog (rock.it-frog.com), DIY effects (coming soon).

LaceSensor

thanks bro ill check ive got the right values at those parts...