NA7RH - Seneca Notes

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This PDF file contains some Heathkit VHF-1 (Seneca) problem solutions and modifications encountered in getting my Heathkit VHF-1 Seneca on the air. (click here)

I had the good fortune to acquire a Seneca that was originally well built and remained relatively unmolested.

The arrangement of items below is in their approximate order of encounter in proceeding through the Testing, Adjustment and Calibration Instructions section of the Heathkit Assembly Manual.

With these changes, I have added no new holes, nor done anything else that is irreversible.

Bob, NA7RH


   VFO Hum, Frequency Shift and Drift when Driver is Keyed

   Tube Substitutions and Tube Condition

   6AQ5 Clamp Tube Oscillation

   2-meter Neutralization and Screen Lead Inductance

   Noise and Hum modulation due to Mike input susceptibility to RF

   Power Supply 120 Hz Hum in Speech Amplifier

   Electric Field Induced 120 Hz Hum in Speech Amp Input

   Arcing Relay Contacts at HV Transformer Center Tap

   Band Switch Mechanism

   Loose Dial Glass

   Link Coupling Assembly Error

   Unresolved Issues with the Seneca


Schematic diagram of the VHF-1 Seneca for reference in support of the above modification notes  (in GIF format).

(Click here for full-page diagram  ~300K)

Front view of the Heathkit VHF-1 Seneca transmitter.

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