Gray 300 ... Any opinion about this amp?

[Xracerx13]

Does that mean you removed Billy's bogus twisted-wire "neutralizing" capacitor?

Then again, maybe someone removed it up the line before it got to you.

Gotta find some pics of that dismal trick.

And for those wondering what I've been blithering about, this amplifier was made with a single unshielded wire connected to the center pin of each coax socket. Each of these would connect to the "common" pin of one relay pole. But the two wires were twisted tightly together for an inch or so between the rear panel coax sockets and the relay.

Twisting two insulated wires together creates a capacitor. And, no joke, the textbook name for a capacitor made from a twisted pair of wires is "gimmick" capacitor.

But this particular trick did not properly cancel out unwanted RF feedback in the Gray. Made it worse, typically.

The cure is a resistor-plus-capacitor negative-feedback network across each individual RF transistor. This technique has dominated what gets manufactured for decades. Just works better.

And if you did leave that gimmick capacitor in place, how the devil did you make it stable?

73

There was no gimmick capacitors per pill. I used a resistor-plus-capacitor negative-feedback network across each individual RF transistor

 

[AudioShockwav]

Gotta find some pics of that dismal trick.

I think this is a Gray 300

 

[nomadradio]

I think this is a Gray 300

Has the correct MRF455, 1994 date is believable.

Looks right, complete with Billy's blasted gimmick capacitor.

73

 

[nomadradio]

There was no gimmick capacitors per pill.

Not what I meant. Just one single gimmick capacitor, on the wire to the center pin of each coax socket. Like in the pic above.

73

 

[Xracerx13]

I pretty sure mine does not have that. I have not been inside it in 5 years and can't find the pics I took of it when it was open.

 

[nomadradio]

I pretty sure mine does not have that.

Count your blessings. It was a terrible idea.

73

 

[70cst]

Old but good reading...

 

[Staybolt]

I had one once. Worked on am but sounded HORRIBLE on ssb.