[Milsurplus] Milsurplus Digest, Vol 61, Issue 3

[Ken Kinderman]

Many thanks to Robert for the encouraging info about what I now hope is
truly a  BC-684. I will try to nail it down by checking the coils.

73,

Ken
W2EWL

MVPA 25615

>
>
> Message: 4
> Date: Sat, 2 May 2009 15:55:57 EDT
> From: WA5CAB at cs.com
> Subject: Re: [Milsurplus] SCR-608
> To: scr274 at gmail.com, milsurplus at mailman.qth.net
> Message-ID: <d41.3dfaa7c9.372dff4d at cs.com>
> Content-Type: text/plain; charset="US-ASCII"
>
> Ken,
>
> Before you go looking for a BC-604-? nameplate, I'll point out two things.
> The bottom plate, with the schematic, is easier to change than the bezel
> with the nameplate.  And they never made a bakelite insert for the crystal
> tray that was different from the 0-79 one.  I think probably because with
> the
> BC-684 having 120 channels, you cannot load all the crystals into the tray.
> And how would you decide which 80 channel numbers were needed.
>
> I had a look at the schematics of the BC-604 and BC-684.  Unfortunately
> there are no glaring differences other than if the transmitter is a
> BC-684-A
> there is no provision for Interphone operation and there is no
> RADIO-INTERPHONE switch.  The BC-684-B and -BM match the circuitry of the
> BC-604-D and -DM.
>  Except that in the BC-604-(*) the tube order in the RF section is
> Oscillator, Rectifier, Doubler, Tripler, PA whereas in the BC-684-(*) the
> Tripler is
> first followed by the Doubler.  The only relatively easy way (unless there
> is no RADIO-INTERPHONE switch) I can see is to couple a GDO to the output
> tank coils L-110 and L-111 and see whether they will tune up to about 40
> MC.
>
> If anyone knows something I missed, please speak up.
>
>