HW-8 problems-any ideas?

[Joseph W Lutz]

Al,

     I am presently taking all the Heathkit Amateur data off a set of
Heathkit Service Bulletins that I got on fiche.  Hopefully when done I
will either make it available for those who would like copies, or will
put in on the BA list to go into the Archives.  Either way, I have copied
the following concerning the HW-8 for your and the Heathkit groups info:

                                                       October 28, 1975
                            Bulletin No.
                                                   HW-8 CW Transceiver
                      HW-8-1
                                                           Service Data

Operating Characteristics

1.  Receiver preselector peaking is done with the preselector (C301) FCW
(Minimum C) resulting in only broad peaks or no peaks being found when
this control is adjusted.

Also, maximum sensitivity may not coincide with maximum noise when
adjusting the preselector.  For example, in trying to locate a Generator
Signal, the preselector would be tuned for maximum noise.  When the
signal is found and the preselector adjusted for a miximum signal, the
defference between the maximum noise point and the noise level at the
maximum signal point could vary as much as 6 db (typical).  Therefore, be
sure to peak the preselector on the signal and not on the noise.

2.  Internal spurious signals may be found at 3.55MHZ, 7.1MHZ & 14.1MHZ.
The levels are approximately .7 to 8 uv.

3.  Receiver sensitivity will increase when the selectivity switch is
switched from the wide to the narrow position.  This is due to the added
gain of the bandpass filter IC-2B and it's associated circuity.

4.  Microphonic levels as compared to the HW-7 have been reduced greatly,
although some still appear on the 80 Meter band.  These microphonics are
noticeable at the lower and center areas of the band when more capacity
is required from the preselector.

5.  The receiver tends to pick up more hum on 15 Meters than on any other
band.  The hum levels on 15 Meters is much less than those present on the
HW-7.

RECEIVER CHECKS:

-  Sensitivity:  1uv or less for 10 db S+N/N

   Typical Sensitivity:   80 Meters     -   .5uv
                                         40 Meters     -   .6uv
                                         20 Meters     -   .7uv
                                         15 Meters     -   .7uv

-  Selectivity:      Wide          -  750 HZ at 6 db down.
                              Norrow     -   375 HZ at 6 db down.

A rough check of the wide and narrow BPF can be made by tuning the
receiver to a signal so that a high-pitched beat note is heard in the
wide position.  Switching to the narrow position should produce a
noticeable decrease in the audio output.

-  Dial Tracking:   Within one dial division.

                                                         Service Notes

1.  Poor Sensitivity:  Poor sensitivity can be caused by either Q1 (Part
# 417-169) or IC-1 (Part # 442-96).  Poor sensitivity on one band only is
usually caused by Q1.

2.  15 Meter Band Adjustments:  The adjustments may be more critical on
the 15 meter band than on other bands.  It may be necessary to set the
mixer coil, check the power output & sensitivity and then reset the mixer
coil.  Check the high & low end of this band and adjust coil L6 to bring
up the end that has the lower output.

3.  Receiver Oscillates on the 80 Meter Band:  When operating the
transceiver at DC input voltages greater than 12.5 VDC, the receiver may
oscillate at points throughout the 80 meter band.  To correct this
problem connect a 10 K  ohm resistor (Part # 1-9-12) across the 80 meter
mixer coil L13.  This resistor is soldered to the coil terminals on top
of the circuit board.  Install this resistor only when needed.

The receiver should not produce undesired oscillations - - - except at
internal spurious frequencies listed in operating characteristics -- when
the DC input voltage is raised to as much as 15 VDC.

                                                            Final Check

The following is a list of physical & functional checks that must be made
before returning the transceiver to the customer:

Physical Checks:
-  All hardware installed & tightened
-  Cabinet & windows clean
-  Plastic feet installed
-  Controls & switches operate smoothly
-  Knobs properly indexed & secure
-  Mark to the left of 0 on dial is aligned with black line on window.
Mark stays aligned when tuning knob is turned further clockwise.
-  Shake test - - - nothing rattles inside.
-  Paperwork in order.

Functional Checks:
-  TX power output - 1 watt or greater on all bands.  Connect a 50 ohm
non-reactive load to the antenna jack.  Tune the dial to 150, key the
transmitter and measure the RF voltage across the load.  The unit is
within specs if the RFV is 7V rms or greater.

-  Typical powr output:            80 Meters    -    1.5 W
                                                      40 Meters    -
1.5 W
                                                      20 Meters    -
1.5 W
                                                      15 Meters    -
1.5 W

-  TX frequency offset:  Approximately 750HZ lower than the Receive
frequency.  Check what transmitter frequency is shifting below the
receive frequency by approximately 750HZ +/- 200HZ.  The amount of
frequency offset does change from band to band.

-  Sidetone is heard in speaker or headphones when the transmitter is
keyed.

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Hope this is of some help.  Good luck!

73 de JOE
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QWCA - NCVA - SOWP - FISTS
Gordonsville, Va 22942 (Orange County)
Looking for:  Heathkit HR/HX-20, MR/MT-1,
              Collins 516F-2, 312B-4, EFJ TR Switch
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