Got my TGSL 100x100 board working, but discrimination doesn't work

[dbanner]

Before I stated 14.9khz, this is wrong, it should be 13.9khz yes.I am sorry I made mistake from bad memory. I apologize.

[yatahaze323]

After testing everything I believe I found an issue at test point 9 in the TGSL101 for the Disc. With Disc at Min it looks correct, however when I turn it up to Max it doesn't look anything like the picture in the TGSL101. The wave seems to smooth out rather than becoming jagged looking like the picture in the TGSL101 instructions.

I replaced the LF353 and I still have the same incorrect wave form with Disc set to max. Any ideas what could be causing this?



Thanks again everyone!

[kt315]

give pic i could read C9 and R19 nominals.

[yatahaze323]

Kt315, do you want a picture of the board or picture of oscilloscope testing c9 and r19?

Thanks!

[kt315]

measured values of them i meant

[Nandor]

It seems that your phase shifter does not works at all. R19 is limiting the Tx amplitude as you increase the potentiometers resistance the sine wave which comes trough R19 becomes weaker, R19 3k3+R18 100K thats why you see a smaller amplitude sine wave. R19 is disc at minimum because you are connected to the oscillator directly there is no phase shift, as you advance towards the output of the LF353 you are getting more and more signal from the 90 deg phase. Check the board and the components for errors, is your 100pF the right value?

[Hyena]

And make sure your output from LF353 is also correct.

[yatahaze323]

So I have a test board that I was working with before my current board, I was using it to learn about the design and the proper location of the parts however the board was sloppy and there were areas that I didn't feel would provide the best end product. But this test board has the correct wave form at test point 9. I compared the wave form at C9 on the test board with C9 on my current board and found that my C9 was where the problem appears to be originating from.

I completely removed C9 from the current board and measured it in the component tester and it measured 98pf. Just to be certain I took another another 100pf cap and it measured 98pf, I soldered that one to the current board and I had the same wave on the oscilloscope. I then removed that cap and found a monolithic 100pf cap, it measured at 98pf. I then soldered that to the board and still had the same wave on the oscilloscope. I'm starting to think there might be an issue with the pcb itself. Any ideas?

[kt315]

maybe you have discussed time ago problem with self-excitation of comparator.
1. open royal sabre schematic of W.Lahr
2. find comparator right above a word 'sabre'
3. look attention on cap 5pF and a resistor from 3 pin on ground
4. copy this way on your board and check

or you might see same matter in my schematic GMT KING COBRA.

[Nandor]

Check the pcb for errors, it seems that the signal gets grounded. I think that there is a short circuit.

[yatahaze323]

I figured out what was causing all the issues. I've been using IC holders and on U101 pin 1 on the IC holder I used bent and curled under the IC holder.

So even though I soldered that area there wasn't even a pin to solder.

Thank you everyone for trying to help solve the problem.

[dbanner]

It's good that you sorted it all out.

[kt315]

https://www.ebay.com/itm/10pcs-DIP8-...4AAOSw-jhUGbnC

[yatahaze323]

Kt315 I'm going to need to buy those ic holders. They look far better than the ones I have.