Heathkit Service Bulletins - SB-104 [Part 5]
Joseph W Lutz
joelutz at JUNO.COM
Sun Nov 2 11:15:02 EST 1997
June 4, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-41
Low Power On All Bands
Change: R-332 from 1.2K to 1210 ohm 1% [PN 2-68-11].
This change will be in -02 level HW-104's and the -06 level SB-104's.
------------------------------------------------------------------------------------------------------------------
June 4, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-42
Improved Passband On 80 Meters
The 80 meter transmitter passband response is being improved by changing
C369 to 390pF [PN 20-106]. This change is being made in the next
production run, and should be made in all SB-104's received for service.
--------------------------------------------------------------------------------------------------------------------
June 18, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-43
ALC Meter Reads Above "3" On Transmit With No
Modulation
Variations in characteristics due to parts tolerances of ZD301 and Q302
will cause the ALC meter to read between zero and 3 when the transmitter
is keyed without modulation, Change ZD301 and/or Q302 until a
combination is found that brings the meter reading below 3 on the scale.
--------------------------------------------------------------------------------------------------------------------
June 18, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-44
Stabilizing 80/40 Meters
The 80/40 output should be stabilized in all units received for service
by making the following change:
Change R345 from 1000 ohms to 100 ohms [PN 1-1-12]
Change R343 from 1000 ohms to 100 ohms [PN 1-1-12]
--------------------------------------------------------------------------------------------------------------------
June 18, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-45
Improving The 40M Transmit Passband
The 40 meter transmit passband can be significantly improved by making
the following change in all units received for service:
Change C-342 from 75pF to 62PF [PN 20-109].
--------------------------------------------------------------------------------------------------------------------
June 18, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-46
Eliminating Transmit Chirp
Chirp may be experienced during CW keying; the following change should be
made in all SB-104's received for service:
Change C6 from 500 ufd to 1000 ufd [PN 25-219].
------------------------------------------------------------------------------------------------------------------
June 18, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-47
VFO Filter Board
A change in screening is being made on the VFO filter board, changing the
board from PN 85-1516-1 to PN 85-1516-2. Components will be deleted from
the new board and the remaining components are being re-numbered, as
follows:
85-1516-1 [Old Board] 85-1516-2 [New Board] Value
------------------------------- -------------------------------- --------
FROM: R-1255
TO: R-1252 150 ohms
R-1254 R-1251 68
ohms
R-1266 R-1253 68
ohms
C-1254 C-1252 105
pf
C-1256 C-1254 105
pf
C-1253 C-1251 .01
uf
C-1255 C-1253 620
pf
The new board will be incorporated in all future productions runs.
-------------------------------------------------------------------------------------------------------------------
June 22, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-48
Change Capacitors To Higher Voltage Caps
Make the follow changes in all SB-104/HW-104's received for service:
Change: C-321 from PN 21-95 TO .1 ufd mylar [PN
27-47]
C-309 from PN 21-95 TO .1 ufd mylar [PN 27-47]
C-906 from PN 21-95 TO .1 ufd mylar [PN 21-47]
This changes the capacitors to ones with higher breakdown voltage
ratings, and increases the RF bypassing.
((((NOTE: PN for the .1 ufd mylar replacement of C-906 is as shown on
fiche))))
---------------------------------------------------------------------------------------------------------------
June 22, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-49
Erratic Display On 10 Meters
Erratic display on 10 meters can be caused by R-1252 loading the VFO
line. Clip and remove R-1252 [470 ohms] on all SB-104/HW-104's received
for service with the PN 85-1516-1 board installed.
------------------------------------------------------------------------------------------------------------------
August 3, 1976
SB/HW-104 Bulletin No:
Solid State Transceiver SB-104-50
Better Carrier Null
A null should be obtainable at two different settings of capacitor C-648;
either setting can be used. If there is only one setting that gives a
null, remove C-645 [33 pF] and repeat the null setting adjustment. If
there is still only one setting that gives a null, install a 62 pF mica
[PN 70-109] capacitor at C-645 and repeat the above step.
--------------------------------------------------------------------------------------------------------------------
************I have so far been unable to find anyone that will load/sell
or whatever, the 1977 Heathkit Service Bulletins. If/When I do get them,
I will 'fill in the blanks'. On the SB/HW-104 Bulletins the No's 51 - to
- 58 were issued in 1977. I will continue with Part 6 with no 59, with
the hope that 'someday' I or someone else will be able to provide them.
Ciao!
73 de Joe W7LPF/4 [NNN0KUU]
QWCA - SOWP - NCVA - FISTS - RCC
Gordonsville, Va 22942 [Orange Co]
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