R-390A
Overhaul Checklist
Mechanical
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Wash gears w/ kero, lube with Bel Ray aviation oil. (tuning friction)
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True 30 slugs RF deck (tuning friction )
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Deburr & adjust Veeder-root dial gears, (tuning friction)
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Tuning drive anti-backlash excess tension reduce (tuning smoothness)
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Meter bearings & zero, check, adjust if sluggish or non zero.
Alignment
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RF deck 30 coils, align slugs & trimmers (signal path)
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RF deck, Q check 30 coils, replace if low, (signal path)
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Band switch, antenna relay contacts: clean, check, adjust (S.P.)
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Ant relay pins, PTO grounding strap: tension adjust, lubricate, clean
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PTO endpoints freq adjust spread (<500 cycles.)
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PTO output Z702: adjust for linearity (receiver sensitivity)
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Tube selection for quietness, gain.
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BFO neutralize (noise reduction)
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Add 4:1 ant. balun. (ground coax shield noise, match & balance ant)
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Add simplified Dallas Langford AGC diode mod. (SSB no CV-157)
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Add 6:1 BFO reduction drive (SSB, synch AM )
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Add SS regulator ground pin 1 (frequency stability)
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Add 10 turn pot (carrier meter zero)
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Add .050” covers w/feet, extra louvers, (diversity stacking)
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Add four CL 80 thermistors (inrush, heat reduction)
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Add diodes to PS (heat reduction)
Additional
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Minimum line voltage test (weak component, tube check).
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Check grids’ resistance (stage gain, AGC threshold).
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Check tube temperatures, (bias, leaky caps).
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Check, clean mini BNCs (signal path)
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Repeat alignment until settings stabilize (burn in completed).
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Check band switch shaft (alignment de-twist if necessary),
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‘Scope check osc. waveform (xtal, BFO, PTO, 17Mc, cal).
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Check T-401 vs xtal trimmer limits
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Check AGC output, threshold, R 544, L514
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Replace C553 killer cap w/600V unit.
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Check Filter caps temp, replace on condition (excess leakage)
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Replace C 609 on condition.
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Burnish PTO shaft on condition
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Remove AF & PS decks, package spare tubes, fuses