Title: V6.3 MORE issues
Post by: WD8BXS on 26. February 2021, 21:19:59
What could cause U2 not to switch on the transmit side??
U1 is working fine, but U2 will not pass the signal to pin 9
I have tried 3 new chips, I have even put U1 into U2 position with the same results.
PTT and PTTN are working fine.
Any ideas??
I am scratching my head!
TNX Chuck, 73 |
Title: Re:V6.3 issue
Post by: DF8OE on 27. February 2021, 09:10:58
Hi Chuck,
please check BAND lines. If these are correct, PTT and PTTN, too, also Chip is not dead the only possibility are the filters themself.
vy 73
Andreas |
Title: Re:V6.3 issue
Post by: WD8BXS on 27. February 2021, 12:52:12
Hello Andreas,
What should I see at the band lines.
I see the PTT and PTTN switching OK.
Thanks,
Chuck |
Title: Re:V6.3 issue
Post by: DF8OE on 27. February 2021, 13:14:40
There must be pulses. You can chekc presence of these signals using scope and toggling bands from lowest to highest. BUT: these lines are also present at the other side band switching circuit. It is impossible that one works and one not if they get exactly the same signals.
vy 73
Andreas |
Title: Re:V6.3 issue
Post by: WD8BXS on 28. February 2021, 20:16:34
:D :D :D
UREKA!!!
The problem was the R3d resistor, in the switching bias circuit.
It was the wrong value
Thanks for all of your advice!!
Take care, 73,
Chuck |
Title: Re:V6.3 MORE issues
Post by: WD8BXS on 01. March 2021, 12:58:03
Well, Now I can't get anything out of the driver stage.
VCC is present, signal in is present, but no output at all!!
I have tried brand new drivers but to no avail, same result.
Also have pulled the final in case of interaction, same result.
Again, any ideas???
Pulling out my hair now hihi
Thanks, 73,
Chuck |
Title: Re:V6.3 MORE issues
Post by: DF8OE on 01. March 2021, 13:14:44
Hi Chuck,
have you stepped through the signal path? Is anything going into the driver stage or is input signal missing, too? For helping over the distance detailed reports are mandatory...
vy 73
Andreas |
Title: Re:V6.3 MORE issues
Post by: WD8BXS on 01. March 2021, 14:53:40
Hi Andreas,
Got it working, I just cleared the board in that area and redid it.
Now the drivers are working, but it is oscillating on all bands.
Full power showing all the time not on freq!
ON to more testing,
This one must be haunted!! hihi
Thanks, Chuck |
Title: Re:V6.3 MORE issues
Post by: DF8OE on 01. March 2021, 16:14:53
Hi Chuck,
seems like a never ending story ::)... Oscillating often is due to bad quality of blocking capacitors at the power supply line of PA MOSFETS and drivers. Also inductors in the collector lines of drivers are often responsible for oscillation. At the end you will win - I am sure ;D
vy 73
Andreas |
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