Scott RCH Receiver

Discussion in 'Technical' started by AG4B, May 19, 2015.

  1. AG4B

    AG4B Member

    Hello all, I have acquired a nice condition RCH receiver to pair up with a DX-100B but have a few questions. I have an original manual and need to replace the PS filter caps. the schematic doesn't list the caps as being electrolytics. What would these be replaced with? I don't see why these can't be replaced with electrolytics. Also looking for 1600 to 8 ohm impedance transformer for the audio out or a suggestion on a suitable work a round. I also need one nice knob to replace the audio gain that has been replaced with a weird non standard knob. I had one of these receivers fifty years ago and always wanted another one. The panel is mint. It receives very well but has some hum from the headphone jack. Any and all assistance will be appreciated. Tom AG4B
  2. WD5JKO

    WD5JKO Member

    Sometimes Hum in the headphone jack can be reduced to tolerable levels by inserting a suitable resistor in series with the headphone circuit. How much depends on the driving impedance, and the headset load impedance. Might try a 100 ohm resistor and go from there. Since you are wanting to convert from 1600 ohms to 8 ohms to drive a speaker, I wonder what the headphone output circuit looks like?

  3. W5HRO

    W5HRO Administrator

    Yes, replace those 4uF caps with electrolytics. I'd bump them up to around 10uF each. The 25uF cap could be changed to 33uF.


    For the 6V6 audio output you can use any single ended output transformer designed for the 6V6, 6BQ5 or the 6AQ5 and the primary will be somewhere around 5,000 ohms. Not sure where you are getting 1,600 ohms from? Anything from Hammond's 125 series should work and the universal 125E would let you choose whatever taps work the best.

    The receiver's manual is also attached below.

    P.S. Nice receiver...

    Attached Files:

  4. AG4B

    AG4B Member

    I have no idea where I got the 1600 ohms from. I think I added a 1 in front of the 600,(typo)..To simplify things, I can I not just use a 600 to 8 ohm matching transformer from the 600 ohm output? TKS, Tom
  5. W5HRO

    W5HRO Administrator

    Yes, that will work. If you ever decide to use a speaker then replacing the stock internal audio output transformer will make it sound a lot better, but you can still use a matching transformer. It's just most of those really old military receivers have crappy transformers with higher Z outputs and produce very restricted audio. If you are only going to use headphones with it though then it really wouldn't matter.
  6. AG4B

    AG4B Member

    I replaced the stock audio transformer with a 5000 to 8 ohm transformer. I works very well and sounds good. My only problem now is that it's broad as a barn. Guess I'll drag out my old Heathkit Q multiplier. The receiver is very sensitive. I only plan to use it for AM. Should pair up well with my DX-100B. TKS to all for the suggestions. Tom AG4B
  7. W5HRO

    W5HRO Administrator

    Yeah, those old military receivers from the late 1930's and early 1940's were usually pretty broad, but it's probably way broader now compared to when it was new. What you have to do is use a wobbulator setup and realign the IF strip and it usually requires replacing a few out-of-tolerence components. Do you have a scope and a function generator that will sweep?

    Anyway, that's what I had to do to my BC-348-K receiver. It's still broad compared to modern standards, but it was like night and day afterwards. I have a old Heathkit QF-1 multiplier I was going to add to mine, but I haven't done it yet. I need to modify the coils for the 915kc IF first.