Heathkit HR-1680

Heathkit

HR-1680

[Block Diagram] [Rear Panel]

Replace the regulator on the D board with a modern design.
[Power Supply] [ [D Board]

[A Brasspounder Improves Heath's HR-1680]
73 Magazine, January 1980, pages 76-78, 80, 82

[Large Full Page Schematic older version]
[Large Full Page Schematic newer version]

[A - Front End] [B - VFO] [C - HFO and Calibrator]
[D - Audio and Regulators] [Power Supply

A - Front End (85-1846-x / 85-2011-x / 85-2072-1)

Two wires to preselector version.

PC Board (85-1846-x)

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X-Ray (85-1846-x)

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Schematic (85-1846-x)

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Two wires to preselector version.

PC Board (85-2011-x)

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Except for C156, X-Ray and schematic same as 85-2072-1 below

One wire preselector mod

Bulletin No: HR-1680-10, July 8, 1977
Front End Oscillates

Make the following changes to correct this problem:

REMOVE: 6-1/2" gray wire which is between preselect capacitor C1B, lug 2, and point B on the FRONT END board. B section of C1 is no longer used.
CHANGE: R417 from 100 ohm to 270 ohm [PN 1-170]. (On board C - HFO and Calibrator)
ADD: 33 pF C156 [PN 20-160] in parallel with C126. Install capacitor on foil side. This will permit proper tuning on 20 M band.

One wire to preselector version.

PC Board (85-2072-1)

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Yes, R103, R104, and R105 are burned and should be replaced.

X-Ray (85-2072-1)

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Schematic (85-2072-1)

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Bulletin No: HR-1680-11, July 24, 1978
Preselector Drifts

The preselector may drift off resonance, usually about one minute after a band change. This is most noticeable on the 40 meter band. To solve this problem install a 10 kilohm resistor [PN 6-103-12] in parallel with C114 and C115. This provides a DC return path for diodes D105 through D108.

Make this change only when necessary.

B - VFO (85-1731-2)

PC Board

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X-Ray

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Schematic

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C - HFO and Calibrator (85-1736-x / 85-1954-1)

PC Board (85-1736-x)

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X-Ray (85-1736-x)

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Schematic (85-1736-x)

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PC Board (85-1954-1)

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X-Ray (85-1954-1)

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Schematic (85-1954-1)

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D - Audio and Regulators (85-1734-6 / 85-2654-1)

Replace tantulum coupling capacitors in audio circuits.

Bulletin No: HR-1680-17, November 25, 1980
Tantalum Capacitor Change

Some Tantalum capacitors have been changed to electrolytic capacitors. Listed below are the capacitors that have been changed.

C207 from [PN 25-223] 47uF Tantalum to [PN 25-915] 47uF Aluminum Electrolytic
C215, C216 and C223 from [PN 25-221] 2.2uF Tantalum to [PN 25-924] 2.2uF Aluminum Electrolytuc

Use the new capacitors when a replacement in needed.

PC Board (85-1734-6)

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X-Ray (85-1734-6))

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Schematic (85-1734-6)

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PC Board (85-2654-1)

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X-Ray (85-2654-1)

The PC artwork to replace the regulator with a LM317 is not available. The LM317 input is right pin (3). the output is the center pin (2).

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Schematic (85-2654-1)

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Power Supply

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