Hallicrafter's S-85 'Dead Zone' after refurbish

Discussion in '"Boat Anchor" & Classic Equipment' started by KD2NOM, Apr 5, 2018.

ad: L-HROutlet
ad: l-rl
ad: abrind-2
ad: Left-2
ad: Subscribe
ad: L-MFJ
ad: Left-3
  1. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Hello,

    I recently completed refurbishing my Hallicrafters S-85 which included the following:

    - complete recapping
    - three wire power cord / fuse installation
    - dial restringing
    - IF / Receiver alignment

    Once completed, I have noticed a 'dead zone' on the dial from about 28 on the index scale to 63 on the index scale. The radio is completely silent in that area on all four band selection settings. Putting the main dial on the edge of the zone and adjusting the band spread does not make a difference.

    I visually inspected the main tuning air capacity and don't see anything obvious - any thoughts on what my next troubleshooting steps should be?

    Thank you in advance for your assistance.

    Mark
     
  2. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    That sounds like a capacitor shorting (most likely the oscillator one). Check the variable capacitor plates VERY closely for either bent plates, or foreign objects between a couple of them, across the entire range of tuning
     
  3. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Will do an report back
     
  4. K9STH

    K9STH Platinum Subscriber Platinum Subscriber QRZ Page

    The spacing between the rotor and stator on the variable capacitor is very close.

    Tune the radio until the signal just stops. Then, using an insulated tool with a sharp tool, touch each plate of the rotor first in one direction and then in the other. Often, the circuit will begin working when the plate is in one direction or the other. Then, very carefully look for why the plate is shorting. Either the rotor plate or stator plate may be slightly bent, there may be something on the rotor plate (pitting, dirt, etc.), or some such. If more than one plate is shorting (possible but unlikely) then you will have to look very closely at all of the plates.

    Glen, K9STH
     
  5. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Genius!

    The last plate of the center plate / stator group was touching ever so slightly - I gently bent it out and viola!

    Now I need to get a decent antenna on it - I have a random wire about 125' on it wrapped around the room but am not really able to pick up anything in the lower bands (below about 5 MHz)
     
    N7ZV likes this.
  6. K9STH

    K9STH Platinum Subscriber Platinum Subscriber QRZ Page

    You should be able to hear all sorts of station on Band 1 (AM broadcast band).

    I would tune my "regular" equipment around the 80-meter band to see what activity there is on that band. Then, while receiving a station, tune the S-85 to the same frequency. You should be able to receive the station about as well as with your "regular" equipment.

    Glen, K9STH
     
    N2EY likes this.
  7. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    rethinking.
     
  8. KM1H

    KM1H Ham Member QRZ Page

    An open antenna coil for the lowest bands is fairly common from a near lightning hit. Use an Ohmeter to confirm a path.

    Carl
     
  9. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    I'm intrigued!
     

Share This Page