[R-390] R390-A problem

[Barry Williams]

Bob,

Changing out 5814s didn't help mine, and there has never been any hum.


Barry
> I'd like to thank everyone for all the ideas. I'm certain it's not the
> function switch as that is fine. It does go back on briefly when the B+
> supply is interrupted and switched back on. I'm first going to sub the
> 5814A's to see if one is indeed shorted as Tim Shoppa suggested, I did
> check them all a year or two ago but the problem was too intermittent at
>   that time to catch and I don't think I subbed 5814A's back then, I
> think i tested them in my tube tester. I also completely forgot about
> freeze spray, haven't used it for probably ten years, an insulated stick
>   is also a good idea. I'll probably start Friday as most of my tools are
>   now in storage. But I'll be back to let you guys know what is going on,
>
>
>
> Bob Young
>
> KB1OKL
>
>>
>> Sounds like cathode to filament short (hum is the smoking gun but the gain shift is telltale too). These are often intermittent. Switching to or through standby interrupts B+.
>>
>> Most likely it's any of the 5814A's and I'm guessing somewhere after the detector.