[R-390] Filters

[rbethman]

I simply used a disk ceramic rated for 1KV.  Just put it in after 
removing original.  Used teflon spaghetti.

Bob - N0DGN


On 2/4/2013 10:55 AM, Craig Heaton wrote:
> Doug,
>
> Something more than the Fluke will be needed to test C551, more to the point
> it has to be tested at rated voltage. In this case 500V. Both of the
> R-390/A's in my shack have had C551 replaced, their insulation resistance
> was zip, nada, zero. The Sprague TO-6A analyzer showed the value (2MF) was
> close but failed on IR. A new cap can be placed under the chassis; NTE makes
> a mylar cap which will fit inside old can.
>
> Craig,
> ____________________________________________________________________________
> ____________________________________________________________________________
> ___________
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
> On Behalf Of quartz55
> Sent: Monday, February 04, 2013 6:24 AM
> To: r-390 at mailman.qth.net
> Subject: Re: [R-390] Filters
>
> Doug,
>
> Well, I'm pretty sure the AGC problem in the one IF strip is confined to the
> IF since the other IF unit seems to work pretty good AGC wise, but I do
> still need to check the AGC action even on the 'good' IF strip.  I see
> there's a test for AGC action in the book, I just need to go through it.
> But even the good AGC one has the 'gain drift' problem, so I'm not home free
> on that one yet either.  I suppose I should fix the drift problem first and
> then go on to the one with the bad filters and no AGC.
>
> I'll check the AGC action tomorrow and see if I can get a feeling for where
> the gain drift is coming from.  It will start off with 150uV 455KHz into the
> IF module giving -7V on the diode load, then it 'snaps' and then 25-30uV
> will give -7V, then it starts drifting around on the diode load meter
> finally resting back at about 150uV in a half an hour or so.  Since it takes
> so long to do this, it's hard to check.  The 2uF C551 checks out OK on the
> Fluke, if a bit high, but who knows what it's doing during warm up.  I need
> to start checking voltages as it warms up.  This may take a while.  I do
> have some tube extenders.  Other problem is one of the pins on P112 is
> broken, keeps falling off and now I've lost it, I need a new P112 for that
> one unless I can swap the line to the unused pin, but then the IF modules
> are not compatable.
>
> Yes, that AGC stuff is pretty iffy to check since so many things are hooked
> to it.
>
> I hope I'm responding to this group correctly, I notice I can't just
> 'reply'.
>
> BTW Tisha, thanks for the link to this group.  I see you are on Lookout Mt,
> but I was thinking of the one at Chatanooga, I've been there for work
> (repeater up there), but it's a different Mt in a different state.
>
>