My TP4 waveform ok?

[GT Blocker]

Hey guys,
My TP4 waveform slowly 'sinks' on the right hand side of the 'valley', though the left side doesn't. It ends up lop-sided like this:



The waveform does change with metal over the coils. Like this:



When I first fire it up, the waveform looks more like Carl's TP4 photos in the instructions, but after a few mins, begins to 'sink'.
Should I move on to the integrator, or stop and fix this?
Any ideas?
Or no prob?
(sorry, the pics are a bit blurry)

Thanks, Gregory

[homefire]

It's not sinking! look how high above zero it goes on the fly back! That's what you are going to sample right!! You must have got your coil capacitance under control! The fly back shows your coil fully relaxed in no time at all.

[GT Blocker]

Educate me, Homefire....

Hey there Homefire!
Could you expand a bit on that? I don't get it. Sounds like I did something right...but, I worry (a SpclFX occupational hazard, I guess ).
If this is OK, I'd like to know why....
Thanks for the quick reply!

[homefire]

GT! After looking at the wave forms Carl posted on the Project plans, Disregard last post.

To me it looks like you have the signals from TP- 1 and TP- 2 out of phase from each other being combined in the Amp TP-4....

See Carl's Figure 22

TP- 1 should be Negative Going!

TP- 2 should be Positive Going!

Together they would combine to form the Signal illustrated by Carls .

Your TP-4 Signal looks like you should see at the Coil!




Trailing Edge of TP-4 Signal should get wider in the presence of metal.



Jim

Sorry about the Paint drawing! All I have to work with!

[GT Blocker]

TP1 & TP2 waveforms

OK...here's a pic of both TP1 (top trace) & TP2 on the scope, Homefire,



TP1 is neg going and TP2 pos. TP2 looks weird at it's base, though,
Ideas? Anyone?

Thanks

[Tinkerer]

GT Blocker,

how much power do you use? It could be that the damping resistor is getting hot.
Tinkerer

[GT Blocker]

TP1 & TP2 waveforms

Hey Tinkerer,
I haven't tried measuring the current draw, but I did just check the damping resistor temp with my digital temp meter for photography. It's only running 3.3 degrees F over ambient, so I guess that's not it. Hmmmm....
What to try next? Could the two coils (DD) interact to cause this?
Thanks for the help.

[homefire]

Tink , I thought of that or no resistor.

GT, The polarity on TP- 4 is not right.

Off Set is scewed too!

Maybe the IC- 6 took a ****?

What does TP- 3 look like?

Bad Resistor on Off Set side of Op Amp?



I'm thinkin you have a short on the op amp TP-3 To TP- 4 or the IC-6 Croked!

Some Op Amps Croke if you go More Negitive then the Supply line!

[GT Blocker]

TP3 (&TP1) traces

oops..gotta repost this one

[homefire]

Top trace is TP-1???

[homefire]

From what I can see you have the top trace blown out real wide .

The second trece down on the voltage.


Notice the second trace is not ballanced with the Offset?

[GT Blocker]

sorry bout that

OK...here's TP1 (top) and TP3 traces
Scope settings are: 10:1 probes, 2uSec sweep
TP1 V/div .5
TP3 V/div 50mv




Thanks, Hopes this helps figure this out....

[GT Blocker]

different sweep setting

Here's TP1 & TP3 again at 50uSec sweep, all else staying the same



If nothing else, I'm gettn' better a shooting pics of the scope! lol

[homefire]

Were is the bottom of those traces comming from?

Never mind, Getting tired here. They should be apposed. I think you chip 6 took a poop!

[GT Blocker]

got me

I have no idea.
I'm wondering if I have a bad passive or transistor (t1 or 2). TP6 & 7 look fine....argh...
I get the same trace on TP3 with IC6 pulled from the board.