Heath Mods

[Mark S Graalman]

  Here are some mods to Heath gear I've done and  happy with,
I thought I'd post them here and those who want to try them can, those
who don't can delete them.

Mark  WB8JKR

Heath HR-10/B receiver:

Low BFO injection level:
 Solder a 3/4" piece of solid insulated hookup wire to pins 9&2 of V4,
connect a VTVM from pin 1 of V5 to ground and turn on the BFO,
adjust the spacing between the wires for a +10vdc indication on the VTVM.

Regulated B+:

 Measure the voltage at the junction of R44, R43, and C56. Subtract 5-10
volts
from this measured value and connect a 5 watt zener of this voltage from
terminal
strip L pin 3 (cathode) to ground.

Regulated BFO voltage:

 Connect a 30 volt 5 watt zener from pin 1 of V4 (cathode) to ground and
change R39 to 33K 1 watt.

 Smoother audio response and less distortion:

 Remove C36

After the above is completed, realign the Osc. and BFO

Heath HR-1680

Excessive hum at low volume levels when using headphones:

 Insert a 10K ohm 1/2 watt resistor in series with the audio line from R4
wiper
to IC202 pin 7, put the resistor on the center lug of R4

Quieter audio:

Replace IC203 with a TLO-84

Heath GR-54 Deluxe SW receiver:

 I.F. interference on AM band:

 Replace R1 (100 ohms) with a 1680 Khz parallel trap, I used a 150-200uH
slug tuned coil and a 50 pf mica.

 Better AM band sensitivity:

Change R4 to 2200 ohms

 Better AGC recovery:

 Change C37 from .2 ufd to .1 ufd.

 Better audio response:

 Change C51 and C52 to .01 ufd
 Remove C53

Heath DX-60B Transmitter:

 Better transmit audio:

 Change C30 and C31 to .01 ufd
 Install a series connected 1 meg ohm 1/2 watt resistor and a .01 1KV cap
 from V4 pin 9 to V5 pin 3.
 Change C17 to .001 ufd 1KV
 Readjust mic gain control

 Better keying:

 Measure the voltage at V1 pin 8 under keydown conditions, subtract
10 to 15 volts from this value and connect a 5 watt zener of this value
from
pin 8 (cathode) to ground.

 Place a .47ufd cap across the key jack.

 Heath HD-1250 dip meter

Better dip response at high frequencies:

Replace the Osc. transistor with a 2N5179

73,

Mark WB8JKR

Sponsored by the City of Tempe 

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