[Heathkit] Re: SB-303 question

[kiyoinc at attglobal.net]

OTAKEBI at aol.com wrote:

> 
> Is it normal for an SB-303 to produce hum when the AF Gain is turned all  the 
> way down.
> The hum goes away when the AF Gain hits about 10:00 o'clock.
> A fellow told me that it was about normal for that rig.
> I can't believe that.
> I have set it up outside (cables to and from  SB-401) and inside (on the 
> board voltages).
> Oh, and yes the hum is present with the SB-303 not connected to the SB-401  
> and with a 50 ohm load on the LMO.
> Any suggestions?
> Or, is it the nature of the beast?
> Thanks,
> Dan/N4VET

Not normal.  You have a bad electrolytic caps.  Probably that big one. 
There's 3 or so in the powersupply so replace them all.

I've seen them dripping electrolyte. That radio is 35 years old so you 
gotta expect the electrolytics to be bad.

Still works well though.  1 kHz read out, stable as a crystal.  .25 uV 
sensitivity.  Good crystal filters.

de ah6gi/4