Re: uBitx V3 transmit probles.


If the blue bias pot is slightly skewed then one lead could be cut. Replace.

Remove Q95 and check gate voltage as you vary the associated preset RV2. It should go from
0-5V. If not replace and set the bias again.


At 09-06-19, you wrote:
I have a V3 that just quit transmitting. It appeared the finals just went out. I replaced the finals (used sockets per advice from another user) and still no output. It is a good thing that I put them in sockets as now one of the new finals is bad. I decided to leave the finals out and test all the Transmit test points per the Diagnostic guide. When I test all the test points, the values are good both in transmit and receive mode, the transmitter section seems to be working as it should.

I hooked up my straight key and tested it in cw mode. The transmit section again looked good as far as the voltages go. Remember there are no finals and on pin 2 of the IRF510 I am getting a voltage reading when transmitting and a constant voltage of 12 volts on pin 2 all the time. Nothing of course on pin 3 as there is no 510 in place.

When I put an IRF510 in each socket, the one in Q94 looks normal but immediately the one in Q95 goes to 10 volts on pin 1. Where is this coming from and why? I have gone through 3 IRF510s in that location now, testing each one on my tester before installation.

Any ideas? Kind of at my wits end (actually that happened when I turned 13, but that's another story).....

Thanks in advance for the always helpful and illuminating ideas.

God bless
Dennis, KD4EPG

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