RCI-2970 troubles

[Space Cadet]

I've got an RCI-2970 (not dx) that is giving me problems. When I unkey, the amplifier self-oscillates and continues to put out about 7 watts, all the while the radio is in RX. If I disconnect the power to the amp, everything works fine. Any ideas? Thanks ~ Vince

 

[Happy_Hamer]

Just curious, what is your SWR? your not using the built in meter on the radio are you? Let us know what the SWR is.

 

[Space Cadet]

Thanks for the reply, however there is no SWR at all, this is connected to a dummyload. I have tried it with different jumpers, different dummy's, on an antenna, no difference.

~Vince

 

[Moleculo]

It's not the SWR. The problem is the amp, or the radio/amp combination. What amp are you using, and what did you set the carrier on the radio at?

 

[Space Cadet]

I guess I could have been more specific...sorry...
I am not using an external amp, just the stock 2-pill built into the 2970. The radio's dead key (with built in amp powered off) goes from about .4 to 6 watts.

 

[wd586]

Possible relay sticking on amp board, most likely needs new pills in amp section.......

 

[Space Cadet]

I have already replaced the pills, and it didn't make any difference. Also, it could be the relay, but the symptoms really dont point that way IMO. It has to be some parasitic or self oscillation coming from the L or C being outta wack, I just dont know a whole lot about amps to figure it out, and of course I dont have a schematic for the 2 pill inside the rig...

Thanks for your help so far...

 

[nomadradio]

The screws that hold down the main radio circuit board also provide critical RF ground connections. Loose ground screws alone can make that radio go totally psycho on transmit.

The two small metal shields soldered beneath the transmit mixer chip and buffer transistor are there to prevent exactly this kind of RF feedback headache. If someone has removed one or both of these, it could be aggravating the problem.

73