Relay Sticking

[Skyscraper]

I got the buzz noise out of the relay. I change the transistor. After about an hour of talking now the relay is stuck. I have to turn the amp off and the relay clicks back. The first key relay sticks and my recieve goes out . What could this be ? any info would be great. Thanks

 

[dxhound]

Judging by your description, that is most definately self oscillations. Your linear is "ringing" or senseing its own output. I bet if you look at a watt meter, even after the radio is unkeyed there will still be a carrier. Dont let it do that for too long or there will be burnt transistors.

 

[Skyscraper]

your right there is a carrier. Whats the fix?

 

[dxhound]

There could be many problems? One is that the transistor you used to replace the keying transistor is overly "sensitive" In other words, It is conducting with a very minute amount of energy being applied. Another common problem is shielding. Try using shielded coax instead of teflon wire (except for the transformers and balances). This should help with stray RF. Another problem could be a high impedance in either the amps output or antenna feed line, in other words, check your SWR and inspect the inside of your amp for any burnt components. A way to possibly test the linear to determine whether its the keying transistor or extraneous RF is to run the amp with the cover off and the chasis well grounded(there should always be a good ground) and see if it is still osscilating. If it does then I would lean toward the keying transistor. If it stops then I would most definately say RF! Good luck with this and I hope you can understand what im writing. Its late for me and Im quit tired.

 

[Skyscraper]

Thank You DXhound it was the keying transistor. There was also a transistor in the circut I took it out and put a fast swiching diode in and everything is working. I saw a couple of pix of the insides of amps and tried to copy the circut. Thanks again.

 

[ss8541]

now this is what forums like this is all about!!

 

[dxhound]

Im just glad to give back just a fraction of what I receive!