Heathkit Service Bulletins - HM-XXXX Series [Complete 66-89]
Joseph W Lutz
joelutz at JUNO.COM
Sat Mar 21 23:02:49 EST 1998
January 27, 1984
HM-9 Bulletin No:
QRP Wattmeter HM-9-1
Update for Manual #595-2979
R1, R8, and
M1
R1 has been changed
from: #6-4991-12, 4990 ohms, 1%
to: #6-5231-12, 5230 ohms, 1%
And,
from: #6-6341-12, 6340 ohms, 1%
to: #6-6651-12, 6650 ohms, 1%
R8 has been changed
from: #6-2872-12, 28.7 Kohms, 1%
to: #6-2742-12, 27.4 Kohms, 1%
The meter [M1] has been changed from: #407-762
to: #407-767
Change the manual to reflect these updates on the following pages:
Page 6,
Page 8,
Page 11, left and right columns,
Illustration Booklet, Page 5, R and C Chart on the schematic.
-----------------------------------------------------------------------------------------------------------------
Thats everything I hold up to 1989 that covers the HM-9. Enjoy!
-----------------------------------------------------------------------------------------------------------------
August 14, 1973
HM-102 Bulletin No:
Watt Meter/SWR Bridge HM-102-1
Possible Shorts Due To Mounting Hardware
The circuit board mounting bolt near R4 -[100K] is extremely close to the
adjacent foil. There is a very good possibility this foil could be
accidentally grounded.
By eliminating the lockwasher and substituting the G-32X1/4" flat head
bolt with a 6-32 X 1/4" round head bolt, [PN 250-31], the problem is
eliminated.
--------------------------------------------------------------------------------------------------------------------
December 23, 1974
HM-102 Bulletin No:
Watt Meter/SWR Bridge HM-102-2
Service Notes
Problems originate because a 50 ohm load is not used for calibration;
even though the kit manual says to use a 50 ohm load, customers use
antennas and even light bulbs. A clue that this is what is being done
wrong is an inablility to null during SWR adjustments. Another clue is
abnormally high power output readings.
If a customer cannot null during SWR adjustment, and he is using ther
proper load, suggest replacing the toroid coil and D-1 through D-3 which
seems to be the magic cure-all for 90% of all the problems encountered
with this unit.
C-4 has been some problem, but this capacitor has been changed to a husky
one [PN 31-57]. The watt meter portion of the unit will not adjust
properly until the SWR balance has been done properly and a good null is
obtained. The indication here is R-6 not adjusting properly. Again, the
toroid coil and D-1 through D-3 is suspect.
Some customers will ask about use of 75 ohm lines. The SWR will be
higher, but collar readings will be within specs. It can be recalibrated
and used with a reasonable degree of accuracy.
A common complaint is the high and low power readings not agreeing.
Explain to the customer the specifications on the meter accuracy which is
plus or minus 10% of full scale.
--------------------------------------------------------------------------------------------------------------------
March 7, 1980
HM-102 Bulletin No:
Watt Meter/SWR Bridge HM-102-3
C4 Destroyed
++++Information not yet available++++
--------------------------------------------------------------------------------------------------------------------
Thats everything I hold up to 1989 that covers the HM-102. Enjoy!
--------------------------------------------------------------------------------------------------------------------
March 2, 1973
HM-2102 Bulletin No:
VHF Watt Meter HM-2102-1
Calibration Problems
Reports have been received of the inability customers are having in
calibrating HM-2102 on watt meter readings. This can be cured by
scraping the area around the hold on the ground foil where the small
spacer fits, when mounting the long bracket. See detail 3B page 7 of the
manual. A good ground connection will make calibrating power readings no
problem.
--------------------------------------------------------------------------------------------------------------------
August 10, 1973
HM-2102 Bulletin No:
VHF Watt Meter HM-2102-2
Inaccurate SWR Null
The shell of the input coax connector is in close proximity to the brass
eyelet come in contact, the SWR cannot be accurately nulled. This is a
problem area worthy of checking before any alignment is accomplished.
Repositioning circuit board on angle mounting brackets will eliminate
this problem.
--------------------------------------------------------------------------------------------------------------------
September 17, 1974
HM-2102 Bulletin No:
VHF Watt Meter HM-2102-3
Calibration Circuit Correction
Perform the modification as shown in the above Pictorial.
(((Pictorial shows foil side of board. Instructions state to: Place C-2A
close to foil side of board, solder to leads of C-2 and foil pads, then
cut off excess lead length. It also lists the following values:
2 Meters
6 Meters
C-2 - 15pF - PN 20-118
C-2 - 15pF - PN 20-118
C-2A - 1pF - PN 28-2
C-2A - 2.2pF - PN 28-1)))
This modification will correct for the internal calibration problem and
make the unit more accurate with respect to actual power input. This
modification should only be done on units which have a glass epoxy board.
Capacitor C2 is increased to 16 pF for 2 meters and 17 pF for 6 meters.
New 16 pF and 17 pF capacitors will be in the line in the future and this
modification may be used until the new capacitors are available.
--------------------------------------------------------------------------------------------------------------------
February 11, 1976
HM-2102 Bulletin No:
VHF Wattmeter HM-2102-4
Separate High Power Calibration
An article in HAM RADIO magazine [February 1976] described a modification
to permit separate calibration of the high power scale.
The article is reprinted below for information only; it is NOT a
production change or service modification.
HIGH POWER CALIBRATION FOR THE HEATH HM2102 VHF WATTMETER
The great crowds of two-meter FM enthusiasts will no doubt provide the
Heath Company with a continuing market for their HM2102 vhf watt meter.
This dandy piece of equipment provides two switch selectable power ranges
of 25 and 250 watts full scale, in the 50 to 160 MHz range, and also
includes a built-in swr bridge.
In checking out my wattmeter I found that everything worked fine with
the exception of a noticeable discrepancy in the accuracy of the high
power [250 watt] range. Checking further, I found that the problem was
due to the fact that R8, a 68k resistor which is used as a meter
multiplier in the 250 watt range, was out of tolerance. The problem
could have been cured by replacing R8 with a new resistor, but it
occurred to me that even greater accuracy could be obtained by replacing
R8 with a variable 100k resistor to allow separate calibration of the
high power range.
This modification is easily done and works out very nicely. The
small trim pot may be supported by using short pieces of solid hookup
wire inserted in the PC board holes formerly occupied by R8. The
adjusting slot should bace upward in the same direction as potentiometer
R6. A hole in the cover plate allows access to R8 when the cover is in
place. This access hole can be labeled high for high power adjust, and
the hole already in the plate for R6 can be labeled "low".
The original calibration procedure calls for adjusting R6, a 50k pot,
in the low power position, which also affects the high power calibration.
With the addition of a 100k pot for resistor R8, the new calibration
procedure is as follows:
1. Using a known power source in the 10 to 25 watt range, and/or
comparing with another wattmeter of known accuracy, adjust R6 for the
correct meter indication in the 25 watt range.
2. Switch to the 250 watt range, and again using a transmiter
with known output, and/or a comparison wattmeter, adjust R8 for correct
meter indication.
Both ranges are now individually calibrated. Any further adjustment
of R6 will require readjustment of R8.
-------------------------------------------------------------------------------------------------------------------
June 5, 1978
HM-2102 Bulletin No:
VHF Wattmeter HM-2102-5
Calibration Problem
If a calibration problem exists, such as power calibration and SWR null,
change:
C3 from 7.7 pF to 1.5 pF [PN 28-4] and
R7 from 10k ohm to 5.6k ohm [PN 1-113]
-------------------------------------------------------------------------------------------------------------------
January 27, 1982
HM-2102 Bulletin No:
VHF Wattmeter HM-2102-6
SWR Cannot Be Nulled
++++Information not available at this time++++
--------------------------------------------------------------------------------------------------------------------
Thats everything I hold up to 1989 that covers the HM-2102. Enjoy!
--------------------------------------------------------------------------------------------------------------------
May 16, 1980
HM-2140 Bulletin No:
HF Dual Wattmeter HM-2140-1
Inoperative
++++Information not available at this time++++
--------------------------------------------------------------------------------------------------------------------
August 13, 1980
HM-2140 Bulletin No:
HF Dual Wattmeter HM-2140-2
Battery Meter Pegs And Unit Will Not Null
++++Information not available at this time++++
--------------------------------------------------------------------------------------------------------------------
January 27, 1984
HM-2140 Bulletin No:
HF Dual Wattmeter HM-2140-3
PEP Readings Inaccurate
Make the following changes to the remote sensor and main unit. Recheck
the calibration after installing these changes. New production will have
these changes included.
Remote Sensor [PN 100-1749]: Change C106 and C107 to .0027 uF [PN
27-141].
Do not disturb any control settings after making the change. Be
sure
to reseal the sensor using a service sticker.
Main Unit: Change: C17 to .022 uF [PN 27-128]
C18 to .033 uF [PN 27-138]
Note: The only accurate method of checking PEP calibration is by using a
two-tone test generator. The FCC standard tones for the two tone test
are 400 Hz and 1800 Hz. A whistle represents only one tone and will give
the same output as a steady carrier [CW] signal. Voice modulation may
give a slightly different reading since the voice is composed of many
tones. The PEP readings should be very close if the AVERAGE power
readings are close. [PEP does not have an accuracy specification.]
-------------------------------------------------------------------------------------------------------------------- August
13, 1980
HM-2140 Bulletin No:
HF Dual Wattmeter HM-2140-4
PN 253-89 "D" Washer Subbed With PN 253-739 Flat Washer
Heath Parts Replacement is now using the PN 253-739 flat washer as a sub
for the no longer available PN 253-89 "D" washer.
The "D" washer was placed over the cable clamps to secure them to the
cabinet/chassis. Since they were no longer being made, Heath switched to
an oversized #6 flat washer as a replacement.
--------------------------------------------------------------------------------------------------------------------Thats
everything I hold up to 1989 that covers the HM-2140. Enjoy!
--------------------------------------------------------------------------------------------------------------------
August 13,
HM-2141 Bulletin No:
VHF Dual Wattmeter HM-2141-1
Battery Meter Pegs and Unit Will Not Null
+ + + + Information not available at this time + + + +
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Thats everything I show up to 1989 that covers the HM-2141.
--------------------------------------------------------------------------------------------------------------------
Okay - that is it for the HM-XXXX Series [1966-89].
73 de Joe W7LPF/4 [NNN0KUU]
QWCA - SOWP - NCVA - FISTS - RCC
Gordonsville, Va 22942 [Orange Co]
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