Mistress won't sweep Part II (with voltages and schematic)

[sjaltenb]

Ok here is the factory schematic for this model.

For those of you just joining, my mistress won't sweep. To see all jokes regarding this, please see my previous thread

Here is the schematic:




Here are my voltages:

LM324N:
.602
5.46
6.83
11.84
1.972
1.92
1.2-3.1 (based on Range turned CCW,CW) although it changes nearly every time i read it

5.86
5.47
5.46
0
5.46
5.46
5.46

E13:0
E12: 2.01 steady
E11: 1.46 steady
E10: 2.03 steady

11.95 Volts out of the regulator.

So, it looks as if the problem is that I am not getting the +7.2/+3.6 sweep that I should be getting out of Pin 8 on the LFO. (U4)

It seems to be in matrix mode no matter what. What gives?

[theehman]

Didja replace the LM324?

[sjaltenb]

Nope, sure haven't.

Is that our suspected culprit? What about some of the caps around it?

[theehman]

Nope, sure haven't.

Is that our suspected culprit? What about some of the caps around it?

I've seen LM324s go bad far more often than caps.

[sjaltenb]

Yeah, Ok well sounds like thats at least the next step

the saga continues. I will order one now and let ya'll know when it comes in.

[theehman]

If you have an audio probe check the pins at each corner of the LM324 and listen for clicking.  If you don't hear any, it's not working.

[sjaltenb]

Yeah I just get silence, like the probe is grounded.

[theehman]

Yeah I just get silence, like the probe is grounded.

Replace it

[sjaltenb]

Thanks! Got one on the way

[sjaltenb]

Replaced the LM324. Still got nothing, the voltages in pin 7 are not changing, they remain stagnant. Sometimes I'll get a ton of feedback, etc. But I think this is because i am working on it out of the case, stuff is flopping all around, etc.

I am really beginning to get frustrated with this one. I just don't see how taking it from one enclosure to another could have screwed this thing up THIS bad.

Help??

PIN8 on the LFO:

In Flange mode: 1.3-1.5 based on range knob
In Matrix Mode:  1.3-8.9 based on the range knob **This is as the schematic says

Other pins:

.583
5.4
3.6
11.73
1.7
1.7
2.3
**This is pin 8 and is 3.92 in both modes. It is not fluctuating between 3.6 and 7.2 as it should.
5.4
5.4
0
5.4
5.4
5.4

[sjaltenb]

I just rechecked it a few times. now pin 8 is stuck no ~5.8 but falls very very slowly 1/100 at a time.

didnt do anything. so bizarre. How quickly should the voltages fluctuate?

[sjaltenb]

FIXED!!! 

Anyone here ever heard of a BAD POT?! Ugghhhhhhhhhhhhhhhhhhhhh The Rate pot apparently was 'broken' or had a short, etc.




Thanks guys!!!!