{Collins} Re: 75A-4 AM filters



Any of the R-390A filters will work in 75A-4 (as well as 75S- 1,2,3 series and 75A-3).
There is a 9 pin miniature plug with solder pins on back. They are kind of like the 8 or 9 pin octal plugs that are used on back of various Johnson, Hallicrafters etc transmitters, except they are 9 pin miniature. I have no idea where to find them. I bought some at a hamfest years ago. When I didn't have them, I just stuck the end of a piece of hookup wire in the appropriate hole(s) in the filter socket. Secured filter and wires with nylon tie wraps.

A slick thing to do is to mount all 4 of the R-390A filters in an external mini-box with a switch, run a cable to the filter socket. Then you can select 2, 4, 8 or 16 kc, or the filter(s) in the 75A-4.

I have also done the jumper trick. As I remember, I used both a capacitor and a resistor. It worked fine. I think this was written up in Electric Radio sometime back. I think it is also floating around internet. Try some google searches. If you can't find it let me know, and I will search my old file boxes.

73

--
Ernie, k0occ 
Atlanta, GA

-------------- Original message -------------- 
From: DW Holtman <future212@xxxxxxxxxxx> 

> Hello, 
> 
> Has anyone tried using an 8 KHZ filter out of an R-390A for a wide band 
> AM filter on the 75A-4? I have a good 8 KHZ filter that is sitting in a 
> drawer. Looking at the schematics, it looks like it should work. I read 
> a couple of notes on the archives, but nothing specific. 
> 
> If anyone has done this, how did you package it? What did you use for 
> the 9 pin tube base, an old tube, broken off? 
> 
> Has anyone just jumpered the input to the output with a cap for a super 
> wide (15KHZ ?) filter. 
> 
> Best, 
> DW Holtman 
> WB7SSN 
> 
> 
> . 
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.
SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
      http://www.collinsradio.org/html/membership.html    -paypal accepted-
.
 NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
  SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
       1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)





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