[NLRS] Sick 736

[Dr. Gerald N. Johnson]

On Mon, 2006-07-31 at 22:31 -0500, John Oehlenschlager wrote:
> 
> My Yaesu 736 is acting very strange with a number of "birdies" on 2 and 432. 
> They occur about every 10 to 15 khz.  Any suggestions?  The operators manual 
> and the detailed maintenance manual are about as useful as congress.  Any 
> help would be appreciated.
> 
>         John O.   K0JO 
> 
The birdies I hear come from the computer monitor and packet TNC. They
go away when I turn those off.

I suppose the synthesizers could make them but even then I'd expect
there to be a signal for phase noise to shift to the IF. I'd be looking
at electrolytic bypass capacitors in the PLL on each band module.
Miniature caps have relatively short lifetimes. If I could find, them
handily I'd likely replace them with tantalum caps for better high
frequency response.

And I'd see if the spurs were there while running it on DC with the
internal switching power supply disconnected. Mine had a dead supply
when I bought it used and it turned out to be three small electrolytics
on the control board. Not power filters. All were bad. I put in the
highest temperature lowest ESR capacitors I could buy (and I'd buy those
from Mouser or Digi-Key) and that supply has worked fine ever since.
-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer