Scott SLRM receiver for sale...

Discussion in 'Amplitude Modulation' started by N2DTS, Sep 29, 2016.

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  1. N2DTS

    N2DTS Ham Member QRZ Page

    I have an old Scott SLRM receiver I got on ebay for $100.00.
    Unfortunetly, the fool just stuck it in a box and shipped it.
    It was not bad before the shipping, but it got a big dent in the front panel.
    It arrived working though.
    It does not work quite as good as it should, I had one in the past and it was a very good working RX, this one seems a bit down on sensitivity.
    I checked the tubes, they seemed fine, did a casual tweaking, not much improvement.
    Everything works like it should, it just seems a bit down on sensitivity.
    Push pull 25L6 audio output tubes, very good selectivity for the day, cw, sharp, medium, wide and broad as a barn door hifi settings.

    Pick up only, pay what you think its worth.
    I have the manual, power cord.

    Located in South Jersey, not far from Philadelphia.

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  2. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    I have one of those. Not really a "communications" receiver, more like a top-of-the-line 1939-era AM broadcast & shortwave receiver re-packaged in a metal cabinet. The quality of construction rivals that of the R-390 series. The dial calibration is excellent for that genre of receiver. Doesn't work very well on CW or SSB; insufficient BFO injection. No wired connection between BFO and 2nd detector, it depends on stray coupling between the oscillator and detector. It was designed to be a "morale receiver" on ships during WWII, primarily for broadcast reception. Exceptionally well shielded to prevent the enemy from homing in on radiation from the BFO and HF oscillator to locate and target the ship. AC/DC circuitry with series-strung tube filaments, no power transformer.

    Because it is so well shielded it might make a good monitor receiver in close vicinity of the transmitter, without the likelihood of distortion due to overload. I believe SLRM stands for Scott Low Radiation Morale or perhaps the M stands for "marine".

    http://www.ohio.edu/people/postr/bapix/slrm.htm
     
  3. N2DTS

    N2DTS Ham Member QRZ Page

    The amazing thing with these receivers is that I have had two and both worked and had the original parts except maybe tubes.
    The original one I had looked like new and worked like it, this one would have been good except for the big dent in the Scott label on the front panel.
    The side pieces with the thumb screws are missing, but everything else seems to be there.
    I made some change on the original to boost the voltage to the magic eye tube to inrease brightness, but forget what I did.
    The voltage is low, and has something to do with the dial lamp, the lamp used directly impacts the volume out of the speaker and maybe the sensitivity.
    An improvement might be to replace the lamp with a resistor and use some LED's for the dial light.

    Hifi audio, no driver transformer, I think its got a 6SN7 phase inverter.
    I put a nice dual cone speaker in the original and with the sealed cabinet, it sounded great.
     
  4. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    That is a very well constructed piece of equipment, nicely built and a clean layout.
    I wish I were closer, I would buy it.
     
  5. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    By the way, as to it's current performance, it might be the bathtub caps needing to be
    replaced or rather, rebuilt using modern polyester caps installed inside. If there are
    any paper caps, especially inside of the transformer cans, they should be replaced as well.
     
  6. N2DTS

    N2DTS Ham Member QRZ Page

    The performance being down might just be due to the pilot light bulb.
    Its in the circuit someplace, a bright bulb gives lower B+ and performance and a dim bulb (lower resistance) gives much better performance.
    I have a little bulb of unknown type in there. I should experiment.
    It has a slight amount of background hum, the electrolytics might need replacing, or maybe they will reform or whatever they do.
    The other one I had had all the original parts in it, nothing was ever replaced except maybe tubes.
    Not sure the other caps need replacing, Scott used some very good components.

    For sale is sort of a stretch, I mostly want it gone without my parting it out, there can not be many of these things left...
     
  7. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    I would gladly take it off your hands, but shipping may be a hassle for you. Let's discuss via PM.
    Thanks!
    Billy
     
  8. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Some radios use the pilot lights or dial lights as voltage droppers for other circuits.
     
  9. N2DTS

    N2DTS Ham Member QRZ Page

    The dial lamp goes across a 3900 ohm resistor from the AC line to the neg side of the HV filter caps.
    The power supply in this radio is something I have a hard time wrapping my head around.

    I am not going to ship this receiver...
     
  10. N2DTS

    N2DTS Ham Member QRZ Page

    Did some quick testing, played around with the dial lamp, putting various resistors in parallel and that did not really do anything.
    Checked voltages, 120 volts and 130 volts on various sections of the power supply.
    As a test, I added 100UF across each cap with no change in anything (caps in the radio are ok).
    I then tried a 1000 volt 6 amp diode across the tube rectifier and the voltage went up to 150, the magic eye tube is brighter (looks normal) and the receiver seemed to work very well.
    Listened on 80 meters and heard VJB really strong, and KA3PTX, WB3FJJ, and someone else on the lower end of the band.
    Fidelity is very good, but I bet a better speaker would make it even better.
     
    WA3VJB likes this.

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