[R-390] AGC

[Guido Santacana]

Hi Larry,

   The death Cap C553 was one of the first to be replaced in the IF deck.
This receiver seems to have very little in terms of mods except for the
diode load access on the front panel. Nonetheless I will check out around
R546,547. The antenna insulator is something that I have not checked but is
on the list now.  I did the resistance checks but found nothing unusual.
The resistance at the AGC jumper connections also came out ok. I made a
list of all the recommendations and one of them will hit the spot for sure.
This hunt will keep me busy this weekend.

   Just one more thing. Please, for all of those in the path of Florence
prepare extra well and follow all instructionsn from the authorities. Don't
try to ride it out alone or in flood prone areas. May God be with you and
protect you. Take care.

Thank you, 73s

Guido KP4FAR

On Tue, Sep 11, 2018 at 7:14 AM Larry H <larry41gm at gmail.com> wrote:

> Hi Guido,  You got lots of good advice.  Hope it's easy to fix.
>
> Are there any mods on the agc line, possibly around R546 or R547?
> Did you do the prescribed resistance checks?  I usually disconnect R545 to
> be sure.
> Is the antenna trimmer insulator pushing good?  Sometimes it gets oiled
> and is bad.
>
> Also, since it was sitting for a while, did the C553 get updated to
> protect the filters?
>
> Good luck.
>
> Regards, Larry
>
> On Mon, Sep 10, 2018 at 4:22 PM, Guido Santacana <gsantacanav at gmail.com>
> wrote:
>
>> Gents,
>>
>>   I will follow through the recommendations starting with the easiest and
>> building up to the most difficult. That will be removing the RF deck
>> again.
>> I should say it's tedious not difficult. A report on findings and final
>> solution will be forthcoming too.
>>
>>  Twenty years ago one of the specimens in my R390 group included a nonA
>> too. I will always regret getting rid of that one. Each one of my R390s
>> had
>> been overhauled and realigned. The only one that came up with an AGC
>> problem was also an EAC unit. This was the first one I ever got. It was
>> from Fair and came as repairable. Z503 had an open coil. Before I got a
>> replacement a common 455kHz IF coil was used as a substitute and it worked
>> until an original came in. I don't know if anyone has tried this before as
>> a temporary solution to a bad Z503.
>>
>> One recommendation I have to save our aching backs from hauling these BAs
>> is to use a scissor table. I bought one that is used for motorcycles and
>> it
>> works great for radios this size.
>>
>> Thank you very much guys and if anything else pops up let me know. It's
>> been a while since I worked in one of these but I am warming up.
>>
>> Best 73s
>>
>> Guido KP4FAR
>>
>> On Mon, Sep 10, 2018 at 4:25 PM dog <agfa at hughes.net> wrote:
>>
>> > Another thing that is often overlooked is the mechanical filters. If the
>> > coils develop resistance to ground it will mess with the AGC big time.
>> > But the only way to figure this out is to disconnect the filters and
>> > measure them, I suppose you could disconnect the AGC line from the
>> > filters and measure the filters resistance to ground individually. It
>> > should be very high, I measure mine using the nanoSeimens position with
>> > the fluke 189. But I'd go everywhere else first.
>> >
>> >
>> > ______________________________________________________________
>> > R-390 mailing list
>> > Home: http://mailman.qth.net/mailman/listinfo/r-390
>> > Help: http://mailman.qth.net/mmfaq.htm
>> > Post: mailto:R-390 at mailman.qth.net
>> >
>> > This list hosted by: http://www.qsl.net
>> > Please help support this email list: http://www.qsl.net/donate.html
>> ______________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:R-390 at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>