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R-390A
Overhaul Checklist

Mechanical

  1. Wash gears w/ kero, lube with Bel Ray aviation oil. (tuning friction)

  2. True 30 slugs RF deck (tuning friction )

  3. Deburr & adjust Veeder-root dial gears, (tuning friction)

  4. Tuning drive anti-backlash excess tension reduce (tuning smoothness)

  5. Meter bearings & zero, check, adjust if sluggish or non zero.

 

Alignment

  1. RF deck 30 coils, align slugs & trimmers (signal path)

  2. RF deck, Q check 30 coils, replace if low, (signal path)

  3. Band switch, antenna relay contacts: clean, check, adjust (S.P.)

  4. Ant relay pins, PTO grounding strap: tension adjust, lubricate, clean

  5. PTO endpoints freq adjust spread (<500 cycles.)

  6. PTO output Z702: adjust for linearity (receiver sensitivity)

  7. Tube selection for quietness, gain.

  8. BFO neutralize (noise reduction)

  9. Add 4:1 ant. balun. (ground coax shield noise, match & balance ant)

  10. Add simplified Dallas Langford AGC diode mod. (SSB no CV-157)

  11. Add 6:1 BFO reduction drive (SSB, synch AM )

  12. Add SS regulator ground pin 1 (frequency stability)

  13. Add 10 turn pot (carrier meter zero)

  14. Add .050” covers w/feet, extra louvers, (diversity stacking)

  15. Add four CL 80 thermistors (inrush, heat reduction)

  16. Add diodes to PS (heat reduction)

 

Additional

  1. Minimum line voltage test (weak component, tube check).

  2. Check grids’ resistance (stage gain, AGC threshold).

  3. Check tube temperatures, (bias, leaky caps).

  4. Check, clean mini BNCs (signal path)

  5. Repeat alignment until settings stabilize (burn in completed).

  6. Check band switch shaft (alignment de-twist if necessary),

  7. ‘Scope check osc. waveform (xtal, BFO, PTO, 17Mc, cal).

  8. Check T-401 vs xtal trimmer limits

  9. Check AGC output, threshold, R 544, L514

  10. Replace C553 killer cap w/600V unit.

  11. Check Filter caps temp, replace on condition (excess leakage)

  12. Replace C 609 on condition.

  13. Burnish PTO shaft on condition

  14. Remove AF & PS decks, package spare tubes, fuses

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