Heathkit Service Bulletins - SB-104 (Part 6)
Joseph W Lutz
joelutz at JUNO.COM
Sun Nov 2 18:10:16 EST 1997
February 2, 1978
SB/HW-104(A) Bulletin No:
Solid State Transmitter SB-104-59
VFO Dead
Check the solder pads at each corner of the PN 85-1205-3 circuit board to
confirm that alls older resist has been scraped away. If the solder
esist is not removed at these points, the oscillator will not run since
the board is not grounded.
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March 31, 1978
SB/HW-104(A) Bulletin No:
Solid State Transmitter SB-104-60
PA Board Cracks Or Transistors Break
When installing the four 360 pF capacitors in the SB-104 "mod kits" on
the foil side of the PA circuit board, mount them as close as possible to
the circuit board to prevent breaking the board or the power transistors
when the heat sink is installed.
These capacitors were added so the PA would be more stable if used with
an antenna tuner on 10 M. Production SB-104A's will have these
capacitors mounted on the component side of the PA board.
Since the vendor is unable to supply us with 360 pF capacitors which are
thin enough to be mounted between the circuit board and heat sink, the PN
830-24 "mod" kits are being inserted to instruct the customer not to
install these capacitors.
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April 4, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-61
R-907 Overheats
During extended periods of operation in the low power mode, R-907 may
overheat.
Change: R-907 to a 1K ohm resistor [PN 1-9].
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April 4, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-62
Broadcast Interference
When operating near strong AM broadcast stations, D-904 will rectify the
signal, causing annoying interference. To remedy:
Add 4.7K ohm resistor [PN 1-8-12] across C-907, thus
reverse-biasing D-904 in the receive mode.
Implement this change only as needed.
----------------------------------------------------------------------------------------------------------------
April 17, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-63
ALC/Filter Board Phono Connectors Shorting To
The Shield
Due to the proximity of the shield [PN 206-1265] to the circuit board,
the possibility of the connectors shorting to the shield exists.
To prevent this, install a piece of fish paper [PN 75-108] on the shield
directly behind the connectors.
Be sure the proper phono plugs [PN 438-46] are used on the cables.
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April 21, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-64
Increased ALC Meter Action
C-827 on the ALC/Filter (K) circuit board should be changed to a .68 uf
tantalum capacitor [PN 25-200].
This change will increase attack time on the ALC loop and decrease the
possibility of "flat-topping."
This will be incorporated in future production lots.
--------------------------------------------------------------------------------------------------------------------
May 24, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-65
Low Or Erratic ALC Action
Relocate diode D7 from across meter terminals to switch S2C, lug 2 to
ground. The cathode is connected to ground.
---------------------------------------------------------------------------------------------------------------
May 24, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-66
40 Meter Not Linear Through Band
Replace C-341 with a 470 pF mica capacitor [PN 20-113]. This will
broaden response and reduce the sharpness of the roll-off.
-----------------------------------------------------------------------------------------------------------------
May 24, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-67
Reduction Of Talk Back
The following steps should be taken in units received for servicing
because of a "talk-back" problem:
CHASSIS WIRING CHANGES
- Move the two large orange stranded wires from J1 to F19.
- Remove and discard the small orange wire between J1 and K3.
- Locate the small orange wire between J1 and relay lug 11. Relocate the
J1 end
to K3.
- Connect a new heavy stranded wire between J1 and H6.
F BOARD CHANGES
- Change R-581 to an 18M ohm resistor [PN 6-186].
- Change R-578 to an 1800 ohm resistor [PN 6-182].
The above procedure should remedy most "talk-back" problems. However, if
a customer isnot sufficiently placated; and only to avoid a refund; the
following procedure may be performed:
SB SERIES
- Move the gray wire from the CW switch, lug 2 to Tune switch, lug 3.
- Remove the jumper wire which is between Tune switch, lug 3 and CW
switch,
lug 2.
- Relocate the white-violet wire from CW switch, lug 4 to HI switch, lug
6.
- Remove the jumper wire from between CW switch, lug 6 and LSB switch,
lug 6.
- Relocate gray wire from CW switch, lug 6, to LSB switch, lug 6.
- Install a 100 ohm, 1/2 watt resistor [PN 6-101] from HI switch, lug 6
to CW switch,
lug ? ((Fiche is unreadable, but could POSSIBILITY be lug 3)).
- Locate the orange wire from F19 to relay lug 11. Relocate the wire end
at relay
lug 11 to relay lug 3.
- Install an orange wire from F19 to CW switch, lug 4.
- Install an orange wire from K3 to CW switch, lug 6.
- Install a 560 ohm resistor [PN 6-561] between F19 and ground.
HW SERIES
- Relocate the diode from between CW switch, lug 5 and LSB switch, lug 6
to
between USB switch, lug 6 [banded end] and USB switch, lug 1.
- Move the brown and gray wires from the CW switch, lug 6 to the USB
switch,
lug 1.
- Move the orange wire at relay lug 11 to relay lug 3.
- Install an orange wire between F19 and CW switch, lug 3.
- Install an orange wire between CW switch, lug 5 and K3.
- Install a 560 ohm, 1/2 watt resistor [PN 6-561] between F19 and ground.
----------------------------------------------------------------------------------------------------------------
May 30, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-68
Mounting Hole Missing At L-815
Presently, two types of ALC/Filer circuit boards [PN 85-2056-1] are being
shipped in the SB-104A transceivers. Both types have the same part
number.
When mounting L-815 [82 uH peaking coil], you will find that one board
has two mounting holes- -the other only one. On circuit boards with only
one hole, connect the second lead of L-815 to the switch, upper lug 14.
When the circuit board with the single hole is packed in a kit, Manual
insert [PN 591-2650] will be included, which shows proper installation
procedures.
The manual [PN 595-1992-01] shows normal 2-hole installation procedures.
------------------------------------------------------------------------------------------------------------------
July 24, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-69
Receiver Overload With Noise Blanker Installed
Occasionally local ham stations cause receiver overload in units where
the noise blanker is installed, even when the Blanker is switched off.
To correct:
- Connect pin 6 of the Noise Blanker to ground.
- Rewire the fron panel NB switch as shown in the schematic at the right.
((Center conductor from Board G/with outer conductor grounded, wired to
one side of switch. Same side - wire from switch to IN on Blanker
Sw/outer conductor grounded. Wire from OUT on Blanker Sw/outer conductor
grounded, to opposite side on NB switch. Other terminal of same side
wire to Board E, with the outer conductor grounded))
This wiring change will route the RF signal directly to Board E when the
switch is in the OUT position.
When the switch is in the IN position, the RF signal will go through the
Noise Blanker.
--------------------------------------------------------------------------------------------------------------------
August 21, 1978
SB/HW-104(A) Bulletin No:
Soild State Transceiver SB-104-70
"C" Board Information
Service Policy: SPC servicing centers may perform standard service
procedures on circuit boards that are in or out of warranty.
Factory-built "C" boards will be warranted for 90 days. BE SURE THE C
BOARD IS AT FAULT BEFORE SENDING IT TO THE FACTORY FOR SERVICE.
The "C" boards are check at the factory on a special fixture for spurious
and harmonic content. The power output is set to 100 watts, +/- 1 dB.
Resistor R-332 may be any one of the following four values:
1180 ohm [PN 6-1181-12]
1200 ohm [PN 6-122-12]
1210 ohm [PN 6-1211-12]
1240 ohm [PN 6-1241-12]
Always replace R-332 with a resistor of the same value. Any deviation
from the selected resistor value on the "C" board will void the warrantly
on the C board, driver board "J", power amplifier board "H" or ALC/Filter
board, "K".
C-342 has been changed to 74 pF capacitor [PN 20-110] in the -02 level.
----------------------------------------------------------------------------------------------------------------
August 21, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-71
Shorted 11-Volt Supply; No Transmitter
Output
If the bare wire on the top of the peaking coils, L-322 and L323 on the
"C" board, is toching the shield plate between the C and B boards, it
will short out the 11-volt supply and/or destroy R-305. To correct,
install a piece of fish paper [PN 75-108] on the shield between the C and
B boards.
--------------------------------------------------------------------------------------------------------------------
August 21, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-72
Low Transmitter Output on 10 Meters
First check to verify the performance of the Driver, PA and ALC/Filter
circuit boards, These boards may be verified by substituting a
"known-good" C board into the unit. All four segments of the 10 meter
band should be checked. Proper power indicates these boards are good.
If there is proper power on 10 meters with the substituted C board,
proceed as follows:
- Reinstall the customer's C board.
- Couple a frequency counter to the output of the C board at pins 23 and
24.
The measured frequency should be 28 to 29.7 MHz, depending on which
segment
of the 10 meter band the unit is operating on. It is possible the 10
meter pre-
driver coils; L-309, L-310, L-319 and L-320 are detuned enough to give
a frequency output of 32 MHz. This is the sum of the premix and IF
frequencies,
rather than the difference. The ALC/Filter board will attenuate this
frequency,
and thus, the unit will indicate low power out on the 10 meter band.
- Readjust the 10 meter coils for the proper frequency output. Follow
with manual
alignment.
- Continue the recommended alignment procedure in the manual.
------------------------------------------------------------------------------------------------------------------
September 26, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-73
Driver Transistors Overheating
CTC devices, with a date code of BY323, at Q-901 and Q-902 [PN 417-830]
on the Driver circuit board have a tendency to overheat. Thisoccurs
mainly in the idle condition. Use only CTC devices with date codes other
than BY323.
------------------------------------------------------------------------------------------------------------------
October 12, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-74
Bandpass Filter Response Check With The IG-57A Sweep
Generator
The are times when in checking the power output of the SB-104, the power
may be low at one end or the other of a particular band. With the
following procedure, this situation can be checked, and if necessary, the
bandpass filters can be trimmed to even out the response.
Procedure:
1. Connect the sweep output of the IG-57A to the SB-104 VFO input.
[Remove the VFO jumper.]
2. Set the generator attenuator to 20 dB.
3. Set the IG-57A to Low Sweep and adjust for wide sweep passing through
the
5.0 - 5.5 MHz range. [This will simulate VFO tuning across the
band.]
4. Connect a signal generator tuned to 5.0 MHz and then 5.5 MHz to the
IG-57A
External Marker input. This is to provide the marker reference.
NOTE: The IG-57A 4.5 MHz marker may also be used.
5. Connect a Demodulator probe to a suitable scope and monitor at either
D6,
Q-304 [collector], C-24 or the RF output jack [LOW POWER OUTPUT
ONLY].
Check the response curves of the various bandpass filters.
This method can quickly isolate the bandpass filter which is causing
the low
power output at one end of the band problem.
A response curve of the 20 Meter Board D bandpass filter which is skewed
low, causing low output at the high end of the band.
5.5 MHz Marker = 17.395 MHz at Board D
= 14.0 MHz at Board C
5.0 MHz Point = 17.895 MHZ at Board D
= 14.5 MHz at Board C
------------------------------------------------------------------------------------------------------------------
October 12, 1978
SB/HW-104(A) Bulletin No:
Solid State Transceiver SB-104-75
VOX Amplifier Oscillation
It has been noted that the VOX may key the transmitter with the VOX gain
fully CW and without a microphone connected. This is caused by an
oscillation in the VOX amplifier.
To correct this, install a .001 uF capacitor [PN 21-140] from terminal
B18 to ground. This will suppress the oscillation in the VOX amplifier.
--------------------------------------------------------------------------------------------------------------------
Okay - time to break and watch a little football. Should have Part 7 -
and Final posted later tonight. Enjoy!
73 de Joe W7LPF/4 [NNN0KUU]
QWCA - SOWP - NCVA - FISTS - RCC
Gordonsville, Va 22942 [Orange Co]
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