Re: I let the smoke out¡
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Oh, my mistake. The band select signal will not change with a change in TX to RX.?
Posting too early, too little coffee.
The other comments remain valid, especially regarding LPF2, and Jeff's services.
JZ
Mike?
I still cannot make heads nor tails of your scope traces. Puzzling. It may have something to do with problems in the LPF array, or maybe more.
Regarding your matrix of voltage measurements:
LPF0 Q509...The gate voltage does not change when switching between T and R! Why not? It is correct that when the gate voltage is 3V the drain voltage should be near zero. This is the correct state for TX. LPF0 would be selected. Approximately 30 mA would flow through the PIN diodes. This circuit appears to be stuck in TX mode.
LPF1 Q510... A similar situation exists here except the circuit appears to be stuck in RX mode. The gate of Q510 is low and the drain is high. That is appropriate to RX, but not TX!
LPF2 Q511... There is a significant problem here. With both gate and drain at zero, it suggests that the transistor has been internally shorted or that a solder bridge exists.
Mike, there are times when it is better to turn away from a difficult problem?and let someone else confront it. (see Shakespeare's not overly courageous character Falstaff, "Discretion is the better part of valor.")
I strongly suggest that rather than putting both you and your radio through more suffering, that you send it off to Jeff Moore for diagnosis and repair. He would provide detailed?info as to what he finds, and so you will still gain some learning.
JZ KJ4A
On Wed, Apr 10, 2024, 5:58?PM < DH8WN@...> wrote: On Wed, Apr 10, 2024 at 11:12 PM, Michael LaBlanc wrote:
Shouldn't the drain of Q509 be about supply voltage
Hello Mike,
yes, but only if the pp voltage of the rf signal is higher than the supply voltage. If not, D506 never is condutive.
73, Ludwig
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