kg7hf@comcast.net wrote:
> Greetings,
>
> I preface this with I am not a EE (I write code for a living) ;)
>
> With the help of a few books, I have attempted to design and build a circuit,
> but I am having trouble making it work consistently without destroying
> various components. I have at least two problems that I know of.
>
> http://home.comcast.net/~kg7hf/Project2/TR_schematic.JPG
>
> The first is that either T17, or Z1, fail after some time, 30 minutes to an
> hour which results in the TR switch staying in the keyed position.
>
> The second is somewhat of a stranger issue, perhaps they are related. This
> circuit is going into a small solid state amplifier circuit 5 - 10 watts in
> will produce 50 - 100+ watts output. When the TR is "working", it seems if I
> excite the amp with 1 to 5 watts, the TR circuit relay RL17 switches on and
> off extremely rapidly, as if RF were getting into the relay and causing it to
> switch on/off, this produces almost a buzzer type effect. As I increase the
> exciter power above 5 watts, the relay starts holding and behaves normally
> (until I get an all out failure). I've tried what I think is obvious,
> ferrite beads, and 0.1uf cap from the vcc to ground at the relays, still no
> change in behavior .
Sounds very much like rf is getting into things. I can't see how
Z1/T17 are being damaged by dc in the circuit if the control input
is a switch to ground as you show. I suggest you add 10nF disc
ceramics on the supply line, switching input, relay coils and each
base-emitter junction.
Other thoughts - it's good practice to have some resistance
base-emitter on T17 to kill the effect of any leakage. 10k or 100k
should do. I think you can probably make R5 and R6 higher in value
and save on dissipation. I'd try 1k and 10k respectively.
Your circuit designing looks better than my code writing :-)
Steve
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|
