[Collins] 312B-4 Directional Coupler Failure

[Gerald Johnson]

The meter and switch are the most fragile indicator parts common to both directions. There are two diodes, probably germanium 1N191, one for each direction. There is a toroidal transformer shielded from the transmission line but surrounding it. Its common to both directions. Its terminated by a pair of low value shielded resistors.

With no indication, I'd check the meter circuit first, then the switch, then the diodes, then the coil and terminations. I'd lay high odds the problem is oxidation of the direction switch contacts. Corrected by a quarter drop of DeOxit.

73, Jerry, Technical Advisor to the CRA.

---------- Original Message ----------------------------------
From: Maciog Henry J Col AFC2ISRC/CCG <henry.maciog@langley.af.mil>
Date:  Tue, 29 Jul 2003 16:52:28 -0400

>Dear fellow Collins enthusiasts,
>
> 
>
>My 312B-4 directional coupler does not read forward or reflected power.
>Transmitted power passes through it, but the values do not register on the
>unit's meter.  I'd like to repair the directional coupler but need some
>hints as to likely causes (as well as where to get parts).  Also, any
>pitfalls associated with making the repair.  Thanks for the help!
>
> 
>
> 
>
> 
>Sincerely,
>
> 
>
>                                                                        Hank
>Maciog  
>
>
>
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