[R-390] R390-A problem

[Robert Young]

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

> 
> Message: 5
> Date: Mon, 31 Jan 2011 13:35:34 -0500
> From: "Shoppa, Tim" <tshoppa at wmata.com>
> Subject: Re: [R-390]
> To: Robert Young <youngbob53 at msn.com>, r-390 <r-390 at mailman.qth.net>
> Message-ID:
> 	<B136EDE3DF5EC441B6F08E0A7AB872450BADD0B69D at EX2K7-CMS-1.wmata.local>
> Content-Type: text/plain; charset="us-ascii"
> 
> 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.
> 

> 
>