SB-104 help and an offer
Joseph W Lutz
joelutz at JUNO.COM
Wed Oct 29 21:19:39 EST 1997
SB-104 Bulletin No:
Here is Part 2 again - for the second time - I have also added both Heath
groups - I hope you get it --Ciao!
Solid State Transceiver SB-104-12
ALC Meter Reads Upscale With No Input
In transmit, it is considered normal for the meter to read as high as 3
units with no input. Therefore, the transceiver is operating properly if
100% modulation occurs at the point where the ALC meter reads 6 units
above the "no input" reading.
11 V. Supply Out of Tolerance
[10.75VDC +/- .5V]
To insure that the 11 V supply operates within this specified tolerance
[10.75VDC +/- .5V] install the following change: R255 from 470 ohm
10% to 470 ohm 5% [PN 1-157]. Install this change only when needed.
NOTE: The low voltage supplies are specified as follows:
5 V. line - 4.5 VDC +/- .5V
11 V. line - 10.75VDC +/- .5V
Distorted Transmission
To prevent distortion when using a microphone with an output greater than
-44 dB, install the following change: R621 from 22 ohm to 100 ohm [PN
1-1-12}
Low or No Output From VFO
Check that the leads of control R1232, VFO Level Adjust, are through the
board and soldered.
Noise Blanker Check
A quick check to determine if the noise blanker is operating is to
intermittently ground the IF output pin at the RECEIVER FRONT END board.
[Pin G-1]. With the noise blanker switch off, noise spikes will cause
S-meter readings of S-9 or greater, and when the noise blanker is
switched on the meter reading will drop to the lower one third of the
scale.
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April 14, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-13
VFO FM-ING
The following changes shuld be made on any SB-104 which has an FM-ing
problem due to battery or mobile operation. These changes will be made
in production as soon as possible.
On VFO oscillator board, change:
R1201 from 4700 to 1200 [PN 1-10]
R1202 from 10K to R.F.C. [PN 45-82]
R1203 from 1000 to 470 [PN 1-6]
R1206 from 47 to 150 [PN 1-66]
D1201 from IN191 to IN458 [PN 56-24]
ZD1201 from 9.1V to 7.5V [PN 56-97]
Although the FM-ing problem may not exist when operating from a 13.8 VDC
power supply, the FM-ing problem would occur if customer operated the
unit mobile, or if his power suply was improperly adjusted. Therefore,
to eliminate this potential problem, the above changes should be
installed in all units serviced.
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April 23, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-14
Improving CW Keying Characteristics
1] Remove two gray wires from lug 6 of R2.
2] Connect the 6 1/2" gray wire from S4 lug 1 to the GRN lug.
3] Discard the short gray wire [that went from lug 6 to the GRN lug].
4] Connect a gray wire from R2 lug 6 to terminal strip BE lug 3.
5] Connect a 5uf electrolytic [PN 25-149] between lug 3 and GND lug of
terminal
strip BE; (+) lead to lug 3.
Note: The lug numbers for R2 as shown on the large SB-104 schematic are
incorrect. R2A [MIC GAIN] and R2B [CW LEVEL] lug numbers should be
interchanged; i/e/, R2A lug numbers should be 3, 2 and 1 with lug 1
ground. R2B lug numbers are 4, 5 and 6 as shown [lug 4 is directly
opposite lug 1 of R2A].
----------------------------------------------------------------------------------------------------------------
May 2, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-15
Improved TR Switching
Change C622 to a 22 mfd capacitor [PN 25-212]. This supercedes bulletin
SB-104-3.
Relay RF Bypass
The switching terminal of the accessory relay is being RF bypassed to
ground to prevent crosstalk within the relay. Very ofter, the customer
elects to ground one of the relay terminals to pin 6 of the accessory
plug. Pin 6 is not an RF ground, although it is at DC ground.
Add a .001 capacitor [PN 21-140] from pin 10 of the relay to ground.
Inadequate Carrier Suppression
In the next manual, the customer will be instructed to look for two null
settings of the capacitor. If only one null is found, remove capacitor
C645 [33pf] and continue with the carrier suppression adjustment. Either
one of the two nulls is correct.
No Receive
L501 Wound Incorrectly
Some [PN 40-1686] coils (L501) were made wrong. The origina coil had two
lugs. The new coil has three lugs and the coils ends have been wired to
the wrong lugs.
The coil need not be replaced. Simply unsolder the wire from the center
lug and move it to the unused lug. The correct wiring is when the two
extreme lugs are used.
-----------------------------------------------------------------------------------------------------------------
June 16, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-16
Insufficient Range
L321 - 3395 Trap
In some cases, C348 may have to be changed to a 620 pf capacitor [PN
20-167].
In many cases, the trap has to be adjusted to a frequency less than 3395
MHz in order to allow for full output on the low end of the 80 meter
band. In cases where the trap cannot be adjusted low enough in
frequency, the capacitor has to be changed.
-------------------------------------------------------------------------------------------------------------------
September 2, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-17
"Blurp" of Sidetone on Initial Receiver Muting When Keyed in Cw
Mode
Change: R564 [820K ohm] to 330K [PN 1-31].
--------------------------------------------------------------------------------------------------------------------
September 19, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-18
SERVICE HINTS
Power Drops on 20 Meters When Unit Gets Warm
Suspect capacitor C909, .01 mfd [PN 21-176] for the above condition.
Direct replacement cures the problem.
Audio Output Transistors Overheating
Change resistor R532, .33 ohm 2 watt to .82 ohm 2 watt [PN
3-1-2].
WWV 14 or 21 MHZ Heterodyne Crystal Fails To Oscillate
Change capacitor C414 from 10 pf to 18 pf [PN 21-60].
Low Power Output on 15 Meters
The values of L317 and L318 are moe critical on 15 meters than any other
band.
Try interchanging coils L317 and/or L318 with any coil from L311 to L316
to obtain the best and most uniform output across the 15 meter band.
-------------------------------------------------------------------------------------------------------------------
October 14, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-19
Inadequate Carrier Suppression
Be sure the carrier suppression trimmer [C649] goes through two complete
nulls for a 360 degree rotation when making the adjustment.
If only one null is noted and the metal part of the trimmer falls to the
left, remove the 33 pf capacitor [C645].
If only one null is noted and the metal part of the trimmer falls to the
right, replace C645 with a 62 pf capacitor [PN 20-109].
This information adds to information found in Bulletin No: SB-104-15.
Transmit - - Audio Input Distortion
It has been found the input preamplifier can be overloaded very easily,
,particularly when using high level microphones.
Replace R207, 4.7 meg to a 1.5 meg 1/2 watt resistor [PN 1-36].
Transmitter Automatically Keys in The CW Mode or VOX Delay
Control Peaks in The
Center
These problems have been traced to leaky capacitors at C208 or C222. In
future runs, these two capacitors are being changed to [PN 27-47].
Also, all the other .1 capacitors are being changed to PN 21-199 on this
circuit board.
Use these new part numbers only if replacement is necessary.
Output Transistor Abuse ByAdvancing The Mike Level Control
Too Far, Or Using Speech
Processor
Advancing the mike level control way beyond the normal operating point or
using a speech processor fills in the valleys in the RF envelope and
increases the output duty cycle.
Operators insisting on doing this should observe the CW duty cycle rating
chart in the SB-104 Operatrions Manual.
Low Power On 15 Meters
Change capacitor C332 from a 75 pf capacitor to a 50 pf capacitor [PN
20-97].
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October 28, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-20
P.A. Oscillations Using CTC Transistors
If you notice any oscillations on the 80 and 40 meter bands using CTC
transistors, add a 390 ohm resistor [PN 1-48] across RFC-902.
The resistor can neatly be tucked underneath the rfc against the top side
of the circuit board.
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Novembe 12, 1975
SB-104 Bulletin No:
Solid State Transceiver SB-104-21
Improved Receiver Sensitivity
1. Remove the wire between G-2 and G-13.
2. Cut the large orange wire 2 1/2" from breakout #7. Connect both
wires to G-2.
3. Change Q-701 and Q-704 to PN 417-274.
4. Change R-719 from a 100 ohm resistor to a 2.2uH choke [PN 45-73].
5. Change L734 to PN 40-1875.
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That's it - will continue with (Part 3) - Sorry for the delay in
finishing this, but had to send wife to Ariz because of illness in my
family there. Will try and get it finish as soon as I can.
73/ZUT! Joe W7LPF/4 [NNN0KUU]
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QWCA - NCVA - SOWP - FISTS - RCC
Gordonsville, Va 22942 (Orange County)
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