TGSL-EDU won't go bleep!

Hi all,
I'm having some problems figuring out why my TGSL won't detect. Any help would be appreciated.
Not sure if the coils are the problem, I've tried 2 home made sets - one set built to inductance specs, the other set matched to frequency of my circuit. Both do about the same thing. I have a tesoro coil ordered so I can rule out my shoddy coil making skills but I'll have to wait for the mail man before I can find out.
Looking at the test points on the schematic, I'm seeing a DC bias signal at the test point in block 12 (maybe .5V difference with something passed over the coils), but I'm seeing nothing at the test point in block 13. No action out of the LM358 pin-7, just seeing the -5V there.
Not sure what's supposed to happen from the other end (from the CD4024 to the audio circuit at block 13). I'm seeing the signal divided down at Q3, Q4 and Q5, but by the time they come together on the other side of the diodes it's basically a flat DC line. According to what I've read I think I'm supposed to see a duty cycle here.

There are 2 LM358's on the board, so I've swapped those around. That made no difference so I'm assuming they're ok. I've checked all the components related to that part of the circuit and see no problems.

I'm getting signals all the way down the line upon detection, RX and TX seem to be good and I've compared all the scope readings in the build guide to my own readings. All looks good but no bleep. I'm wondering if it needs a certain amount of signal before it will register, so maybe could still be the coils?

Any pointers please? This thing is driving me nuts.

Paul.


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Seeing a bump of about 30mV on detection at the source pins of TR4 and TR5.

Posted on: October 23, 2011, 07:31:21 PM

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doh, was looking at the wrong pin. Here's gate and source. Source signal increases about 1V on detection. Same thing on both TR4 and TR5.

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Sorry, I'm getting all sorts of confused here. Been staring at this thing for way too long. Previous pic was gate + drain. The source just has a DC signal. From what I understand (from TGSL 101 pdf) the signal from the TR4/TR5 is taken down to a DC signal by C12 and C15. I am seeing a DC signal at pins 3 and 5 of u103a/b which bounces about 1V upon detection. That signal seems to be coming through all the way to the input of u107a pin 5 (LM358) but isn't showing up on the output at pin 7.

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http://www.thunting.com/smf/index.php/topic,28081.msg199374.html#msg199374

It's the TGSL build guide. Got a lot of handy info in there, but doesn't go into quite enough detail for me to figure this one out.

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http://www.thunting.com/smf/index.php/topic,28081.msg199385.html#msg199385

TGSL 101 part 1 is attached to that last post I made. There's a part 2 also, but it's just a guide on vacuum forming coil housings in a kitchen oven (my wife's gonna love that part).
Let me know if you want that posted too.

I think I'm going to order another TGSL kit + breadboard it (what I should have done in the first place). That way, if it all works I can use it to figure out what's going on with the current one, and if I find a problem it's nice and easy to tinker with.
That means I'll end up with 2 TGSL's. I can throw the Tesoro coil on one + use the other for testing home built ones.
Always nice to have a spare 

P.

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