Yaesu FT 101E issued during tuneup

[K9FON]

I got a used 101E the other day and i have noticed whenever i advance the preselect load and tune caps when transmitting i get a loud crackling sound in the receiver section when at resonance.. I just replaced the final tubes and the main filter caps but i still have the noise at resonance... Any hints or help appreciated. Snide comments are NOT appreciated....

[AF6LJ]

I got a used 101E the other day and i have noticed whenever i advance the preselect load and tune caps when transmitting i get a loud crackling sound in the receiver section when at resonance.. I just replaced the final tubes and the main filter caps but i still have the noise at resonance... Any hints or help appreciated. Snide comments are NOT appreciated....

Have you followed the reccmonded procedure to neutralize the PA (final output) tubes?

[K9TW]

Are you loading with a wattmeter in the output and monitoring IC (plate current). If so, at resonance (plate current dip and rf output max) when you hear this "crackling" sound what does IC do? What does RF output do? When crackling does plate current (IC) spike up?

Does the crackling occur more as you rotate the Loading control? The load control air variable has very close spacing and if arced over at any time in the past you will have burrs and pits at that spot and it will easily arc over and make a frying sound. Terry K9TW

[K9FON]

Yes i did as per the Fox Tango website..

[K9FON]

At resonance it makes the cracking noise and the IC spikes.... Im using an MFJ wattmeter and a dummy load..... It only does this when the voltage is applied to the tubes. With the heater switch off there is no noise in the receiver when the controls are all peaked.... I went ahead and ordered a cap set of of EBay and im going to replace all the old caps with new ones....

[K9TW]

As Sue suggested after installing new finals you need to perform the neutralization procedure as described in the service manual. Often nothing happens when you dont neutralize replacement tubes especially on lower bands but it is standard practice to do it. Do you have RF probe and VTVM or an O-scope. If not, it is a little difficult to do a good job of neutralizing. The sound you describe sounds more like tank capacitor or load capacitor arcing over and not tube oscillation.

With heater off you will have no RF drive and no voltage across either pi-network air variable capacitor.

Not sure why you would want to replace all electrolytics?

When you say at resonance do you mean at max rf output on your wattmeter following the Yaesu loading procedure?

Anytime you adjust the Plate (tank) capacitor for minimum IC you are at resonance. Do you start with the Load capacitor full CCW or nearly so and if so does it make the noise at some point as you turn the Load capacitor CW direction? Does it do this on all bands?

[K9FON]

Nope no scope or fancy troubleshooting gear here at my QTH. All i have is a wattmeter and a couple of VTVMs. I had a scope but i sold it to someone that wanted it more than I did. It makes the noise no matter where i set the load caps.... It does it no matter what as long as i apply voltage to the finals... I have a working EX that im going to swap some boards around with the E and see if i can square away the problems..

[K9FON]

I just removed the final tubes and applyed the high voltage with no tubes and the noise wasnt there. So im guessing that the issue is with the tubes i installed..

[N8YX]

Check the screen-blocking capacitor which couples the driver output to the PA input. A defective (intermittent) unit can cause the condition you describe.

You actually have to be transmitting with the rig and therefore generating RF power for this problem to occur, correct?

Further:

I just replaced the final tubes and the main filter caps but i still have the noise at resonance

Did the problem exist with the old set of tubes?

If so, what are the differences in them? (Manufacturer, lot #s, etc.)

[W0JBC]

Nope no scope or fancy troubleshooting gear here at my QTH. All i have is a wattmeter and a couple of VTVMs. I had a scope but i sold it to someone that wanted it more than I did. It makes the noise no matter where i set the load caps.... It does it no matter what as long as i apply voltage to the finals... I have a working EX that im going to swap some boards around with the E and see if i can square away the problems..

The gear has an issue in the final ( tube ) section . With no test equipment , you are at a dead end .


Since this has not been ' WIKed ' YET , do not change out boards if you do not know the theory .

I have had an FT-101 E for many years . I never have experienced the malady you describe .

My radio was NEVER on the 11 meter band . There might be other issues before the final stage that might be defunct .

Get a good radio technician with a ' scope and even better test equipment .

That radio has been a work-horse .

Understanding theory always helps . Good luck .

If repaired CORRECTLY, it will serve you well ..

J.


PS I have three ( 3 ) logbooks filled with CW contacts using my ( FT-101E ) radio . It was not a CB radio .


Now it is time to get WIKED .