Yaesu FT-401b

[Radio Tech]

Anyone worked on one of these before?
I have one here in the shop that is driving me nuts. The radio receives ok but has no power out. I changed the driver and finals with good tubes and same results.

Also I have checked the voltages on both driver and finals and they agree with the manual. Tested all the coupling caps.

One strange thing is when I scope the input of the driver (pin 2) I see RF. But on pin 7 I get a saw tooth wave form on both TX and RC. I also get an RF signal at the antenna jack. Just no power out.

I see a signal on the SA so I know the mixers are working. Bias supply seems ok, Good enough to smoke the 2 100 ohm resistors if cut up too high.

Anyone have any ideas? May have to youtube this one.

 

[TonyV225]

Almost seems as if theres a leaky cap in there.

 

[Radio Tech]

Possibility yes. And I think the problem must be in the driver stage.

 

[Birddog2009]

Hmm i have one that transmits great but the receiver is dead. I have replaced all the tubes with new ones and still nada.