Hello, it’s me again. Now my Shruthi is almost working: everything seems okay except for the resonance setting. It doesn’t affect anything. I mean one from the patch setting. It goes fine to the filter board and up to R8. I can’t measure it after it. Filter nicely resonates and R34, R35, R23 and R3 affects it. I measured all the board I think, and the only problem I get is shortened 12th ant 13th leg of IC4. Is it okay for them to be shortened?
Hmmm, what do you mean by shortened? How do you test that?
There might be something fishy here because IC4D (the 4th op-amp cell in IC4, the one on pins 12/13/14) is generating the current controlling the resonance VCA.
Resistance is close to zero between them. There is no such thing on other cell (pins 2 and 3 for example).
With the board powered off, I read 1k of resistance between the two input pins, if this can be of any help. Measuring resistances between pins of IC doesn’t mean much anyway…
It doesn’t mean much but pin 13 surely shouldn’t be grounded ))
I solved this problem anyway. Now working perfect and I love it. But that was tricky. That’s what I did, just if someone interested:
Pin 12 was somehow shortened with pin 13 and both of them were grounded. So there could be some problem between pins 12 and 13 or somewhere else. Somewhere else could only mean some part before transistor was grounded (D2, C6, R8 or R9). I double checked them and found no problem. Then I de-soldered IC4 socket just to be sure everything is fine on the top side of the board. It was ok and pins 12 and 13 were both grounded even with IC4 socket removed. So the problem could only be somewhere in the board. I had no intention to check every path between R8 and Q1 so I just de-soldered all of the parts path between which could be grounded, and connected them to pin 13 of IC4, bypassing the board. Here is the photo is case I’m not good at explaining: http://farm6.static.flickr.com/5015/5477824220_7865e2ddce_o.jpg
Doesn’t look very sexy but works ))
I think that if I am right about the board fault, someone owes me a beer ))