[R-390] Troubleshooting the R-390A Rf Module

[DW Holtman]

Joe,

Thank you for the response. I swapped the tube with V401 from the xtal 
oscillator sub chassis, which is well used.

Roy,

I have been thinking about the same thing. I will next pull out the RF 
Module again and while it is out, change out C324, C324 and  C326. I have 
them on hand, and it will not be too tough. Also remove one end of L201 and 
check it. It is on a very low voltage circuit so an inductance check should 
work.

Thanks for the help.

Best,
DW Holtman

----- Original Message ----- 
From: "Roy Morgan" <k1lky at earthlink.net>
To: "r-390 reflector" <r-390 at mailman.qth.net>
Sent: Wednesday, March 25, 2009 7:06 PM
Subject: Re: [R-390] Troubleshooting the R-390A Rf Module


>
> On Mar 25, 2009, at 8:31 PM, DW Holtman wrote:
>
>>
>> Hello,
>>
>> I have an unusual problem.
>
> The best kind!
>
>> ... the 17 MHZ xtal oscillator V207 does
>> not want to turn on. ... a tube extender ... it starts working.
>
> Oscillators can be the most difficult circuits to make reliable when
> they are acting up.
>
>> Does it
>> want more/less inductance or capacitance?
>
> Maybe more capacitance
> (Pause to look at the schematic ... )
>
> Notice C324 and C325.  They form a voltage divider and feed back path
> to make the thing oscillate.  One of those caps may be bad.
>
> Also at pin 6 is the screen bypass cap C326, 5000 pf to ground.  An
> easy test for that one is to put a similar cap in parallel with it.
> You may be able to wind a parallel cap around the actual tube pin.
>
> Of course if the cathode choke is mis behaving, that would cause
> trouble.  If  you can measure inductance a tube pin to ground test
> there would tell you if the choke is shorted.
>
> Roy
>
>
> Roy Morgan
> k1lky at earthlink.net
> 529 Cobb St.
> Groton NY, 13073
>
>
>
>
>
> ______________________________________________________________
> 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