White 3900D

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Do you have your final layout in Sprint please DB?,,Thanks,,Marty

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Sorry folks, I uploaded the wrong file

Here is the final sprint layout. I am etching my pcb today. I'll show pics of the outcome, whether good or bad.

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Blue plot is output of LM393.(ltSpice)
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393 reacts just on knob RESET. in your plot its like a generator. bad.

The blue plot is the output of U3/1. The reset switch toggles U3/2 output to HIGH/LOW. LM393 is a dual comparator chip.

I should have made that clear before, so thanks for pointing that out.

The output of U3/1 is the gating pulse which is supposed the provide a balanced signal to the inputs of the differential amplifier U2/1 of LM324.

[MartyJ1963]

Do you have your final layout in Sprint please DB?,,Thanks,,Marty

[kt315]

translate a text on sch. on output of the 393:

in standup logical 1 (H - high level, near +E)
closed S2 (S2 is knob RESET) gives logical 0 (L - low level, near -E)

[kt315]

Blue plot is output of LM393.(ltSpice)
---
393 reacts just on knob RESET. in your plot its like a generator. bad.

[SWL]

Board file extension?

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Here is my final layout. I intend to go with this one. The circuit is checked as best as I can, and everything looks good according to the original circuit. Any errors will have to be corrected afted construction and testing.

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Blue plot is output of LM393.(ltSpice)
Red plot is the Tx waveform after VR1. The DC offset of the blue plot is wrong because I use 0 as common whereas the actual circuit is 1.7v.
It is just to give general idea of what to expect at analog switch... a square pulse.

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I warn everyone who is interested, please do not attempt to build this circuit unless you know what you are doing!
Otherwise wait until I have tried to make a good working prototype. It is a learning experience for me, and I don't mind being disappointed.

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Pin2 LM324 not connected [ATTACH]48302[/ATTACH]

Yes thankyou, I saw couple more little things as well.
All has been corrected and verified, soon I will put the final version. You have good hawkeyes!