GGG Maestro Ring Mod layout problems

[Ry]

I've been working on the Maestro Ring Modulator (board and IC purchased from GGG, thanks JD!) for the last few weeks with little success (no output).  I finally noticed that IC4 was getting awfully hot.  Closer inspection reveals that pins 1 (output of side A), 8 (+15v) and 5 (+2 input) don't have traces running to the pads.  

I have yet to fix this on my board as I just realized it when I was drifting off to sleep last night.

Ry

[jsleep]

Hi Ry,

pins 1 (output of side A), 8 (+15v) and 5 (+2 input) don't have traces running to the pads.

That is the correct pinout for a standard single opamp e.g. 741, etc. as specified.  Sounds like you arre using a dual there e.g. TL072?  Just so you know the layout has been verified by Alex (Zero the Hero).  I think he's around here quite a bit, so if you have any other questions, post 'em here.

Thanks,
JD Sleep

[Ry]

Aw shoot, you're right (insert sound of forehead being slapped), I got it confused with one of the 1458's.  Sorry for the post.  I do have a 741 in there and it is running a little hot.

I must have a short somewhere else, or my P-fet is wrong.  I just grabbed the ONLY P-fet at Fry's--an NTE model.  Time to rig up an audio probe.

Thanks!

Ry

[Zero the hero]

I don't think that the JFet could be a problem, I didn't used the original one. the circuit built around the 741 is the internal oscillator. Build an audio probe and check the test point A. By moving the trimmer TR5 and the pot PT2 you should hear the sine oscillator.
This part of the circuit IS A REAL MESS: check all the connections for SW1, and PT3. For simplyfing the mess, use jumpers instead of J4 and J3 phone connectors, and remove J5 (oscillator out) which is now useless (you can mount it later, when you'll get this beast working).

[Ry]

I had the P-fet in backwards (the nte diagram on the back of the package was impossible to figure out).  So it works with a LOT of bleedthrough.  Trimmers #1 and 3 don't seem to do anything.  I used 25 turn pots that may not be working correctly.  I'm going to replace them and try tuning it again.

Thanks!

Ry