[R-390] R-390a dead below 8 Mhz

[rbethman]

Matt,

One piece in collecting Roger's tips.  This came on reflector in 2005:

>
> You need a minimum tube test set of each type tube in the receiver. 
> (More is
> good but not required) For every tube type you need N-1 tubes. There 
> is one
> 6DC6. N-1 is zero 6DC6 in the tube test set. There are 3 6C4's one is 
> in the
> first mixer. Above 8 MHz the receiver uses only two of the 6C4's So 
> N-1 is 1 6C4
> in the test set. The 26Z5 are sand state and need zero. The 0A2 either 
> lights
> or got replaced. N-1 is zero 0A2. The pair of 5654 AKA 6AK5 needs 1 
> The three
> 6AK6's need 1 because the line and local are in parallel and you only 
> meter
> one branch. You need 4 each 5749 AKA 6BA6. You can grab the 5814's out 
> of the
> calibration area and V509 for the theses test, but 3 each 5814's help.
Note the 6C4 - two for ABOVE 8Mc.  Three total.  Try swapping one for 
another.  I'd use a "known" in use one for the No. 1 6C4.

Good first idea that I see.

Bob - N0DGN

On 4/18/2010 3:35 PM, mparkinson1 wrote:
> OK I will help jump start this reflector.
> I have not seen to much action except on the Cosmo PTO issues.
>
> So here it goes dead below 8 MHZ
> could it be T207 shorted or could it be the 100PF capacitor shorted under the transformer.
> Could it be the Switch under the RF deck misaligned???
> The RF train is aligned ok for 7MHZ plus.
> Could it be the 17Mhz osc dead not likely.
> Hum did I miss something else please chime in guys this is good for the reflector archives just jump starting something else.
> This is a famous problem for sure.
> Matt Parkinson Military Equipment&  R 390A Depot Center
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