[Boatanchors] 275W Matchbox

[Garey Barrell]

Larry -

The Matchbox receiver tap was connected to the '300 ohm' point on the coil from the factory.  The 
idea was to select the coil tap that best matched the receiver input impedance.  Many older 
receivers were 300 ohm or higher input impedance, only a few were anywhere near 50 ohms.

Sorry, I don't recall just where that point is, but the bottom line is that you can put it just 
about anywhere!  I would tune in a steady signal, and then move the tap from turn-to-turn for the 
highest signal level (best match?)   I remember seeing some where the receiver tap had been 
converted to a clip lead to allow easy changing, I guess for various receivers.  All those 
screws?????    I don't think I'd ever change it!!  :-)


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>


telegrapher at q.com wrote:
> After receivein pictures of the innards of several members 275W matchbox, an issue is still at large.  Every one i've seen showing where the receiver and transmitter taps are on the coil form are different.  One had the receiver tap on the turn closest to the rear of the box, one hd it on the 2nd turn from the front and another (mine) was on the middle or 3rd turn of the coil but there are marks on the coil stock that show it could ahve been on the first or 2nd turn from the front as well.  So just where is the correct tap for the receiver?  The transmitter tap is on the middle winding at the bottom (underneath) the coil and is soldered in place.  I suspect that is where it should be.
>
> I also notice that my unit has a pair of resistors in parallel that are in the 115 relay loop, mounted to a terminal strip along side the relay.  I didn't see that in any of the other pictures and it doesn't show on the schematic either.  Maybe used a lower voltage?
>
> Last night i hooked the Viking II relay wiring to the box.  Guess what!  Relay doesn't operate.  gotta pull it out of the box again.  Maybe that was one of the reasons the relay was bypassed when i received the unit, it was defective.  Grrrrrr.  One of these times i'm gonna count the screws.
>
> Larry
> W0OGH
>