[Collins] 75S-3C Birdies

[Dr. Gerald N. Johnson]

On Fri, 2006-07-14 at 20:38 -0400, carl lowry wrote:
> Thanks guys to everyone of ya'all who e-mailed me about my Birdies.
> Most of the e-mails recommended tightening all the screws around the tubes, & elsewhere,
> and replacing several tubes in the RF & IF sections.
> Well, we did that & glolly geee... no more Birdies...
> The only recommendation i just couldn't relish myself into doing was one guy recommended
> taking a shotgun to the receiver "just to get rid of the Birdies".
> Still low on volume & sensitivity as compared to my KWM-2A.
> But I'm a working on that one.
> Again ... Thanks guys
> Best 73s
> Carl, k4zrd

For low audio, be sure the 6BF5 isn't old and tired. And that the black
beauty connected to the control grid has been replaced by an orange
drop. The leakage of that black beauty will hasten the aging of the 6BF5
(while increasing the scorch on the cabinet lid). Then be sure you are
using a 4 ohm speaker, not an 8 ohm speaker. Go for a larger speaker
that is enclosed with a bass port. The tuned port bass reflex speaker
enclosures have significantly higher efficiency than speakers that
depend entirely on absorbing the back wave.

Be sure the capacitor from 6BF5 plate to ground isn't leaky or changed
to a higher value. If its a black beauty, replace it with an orange
drop.

And while a 6AQ5 will produce audio, it can't do the power of the 6BF5.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer