Tag: Blown Finals Club

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Yaesu FT-817My precious FT-817 still is lying around in the shack unable to transmit. I’ve studied the service manual and did some measuring around in it. Regular readers of my blog know that a while back suddenly my Yaesu broke down due to shortage. It seems like a capacitor on the voltage input blew and took something with it. I let the input fix by a local service shop but that alone cost me already 75 euro’s. So now the Yaesu is able to receive again, but still no transmit.
My intention is to fix that myself. The local repairman told me it’s probably due to blown finals that the rig isn’t transmitting. That would make me a member of the “Blown Finals Club”. But I’m not quite convinced by his story. When only the finals are blown, you should get a very faint signal as output. But there is absolutely no signal at all. Not even when I take another receiver and poke around with that antenna in the transmit line of the Yeasu, no signal at all. So maybe the oscillator or driver stage must be (also) broken to get this behavior.

This would be my very first big repair job, there for I’m not in possession of various measuring equipment. The only measuring device I have is a multimeter. That won’t bring me very far in this case. Fred, PA3YH has a Multimeter which can measure HF-signals. A RF-millivolt meter, such as referenced to in the service manual. But it has a maximum reading frequency of 100 KHz. The RF-millivolt meter reads like 2,6 volts AC on the output of the oscillator (the service manual says it should be 66mV). But the output signal from the oscillator has a frequency of 65.875 MHz. So it’s logical the meter is not reading the correct voltage.
Okay, so I don’t know if the output of oscillator is correct, but I DO know that the oscillator has output! So I guess now I should look to the first driver stage.
But I think I’ll look for someone with a good scope first. It’s easier to check all the checkpoints in the service manual and also check if they have the correct value.
If anyone has good tips on how to find the problem, let me know!