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Hi Chris: Here you go..........................<br>
Merry Christmas !!!!!!!!!!!!!!<br>
Van<br>
73<br>
wd8aam<br><br>
This is the Heaethkit (and other manufacturers) Service Bulletin
WEBSITE: And MUCH MUCH MORE Heathkit information.<br>
<a href="http://www.nostalgickitscentral.com/" eudora="autourl">
http://www.nostalgickitscentral.com<br><br>
</a>NOW,, all the SB-401 Service Bulletins:<br><br>
<a href="http://www.nostalgickitscentral.com/heath/Service_Bulletins/sb-sb401.pdf" eudora="autourl">
http://www.nostalgickitscentral.com/heath/Service_Bulletins/sb-sb401.pdf</a>
<br><br>
<br>
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<br>
</b></font>At 12:42 12/25/2014, you wrote:<br>
Hello and Merry Christmas. Van,<br>
<br>
You certainly delivered a nice Xmas present to the SB-102 owners by
sending all the Heath SB-102 service bulletins! J<br>
<br>
Do you by chance have or know of a source for the SB-401 service
bulletins? I suspect where there is some common circuitry in the
transmit chain, the SB-102 SB’s might apply.<br>
<br>
Thanks es 73,<br>
Chris<br>
W7JPG<br>
<br>
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</font><font face="Times New Roman, Times" size=5>[No date on fiche]<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-1D<br>
LMO Change<br>
The [PN 110-32] is no longer available. In order to use [PN
100-40-LMO]<br>
it is necessary to add decoupling capacitors [See SB-101
installation<br>
procedure].<br>
----------------------------------------------------------------------------------------------<br>
May 15, 1968<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-2D<br>
Filter Choke Replacement<br>
PN 46-36 filter choke 4.5H @ 120 MA is replaced by PN 46-32 filter
choke<br>
4.5 H @ 150 MA. This part should only be changed when the original
has<br>
failed.<br>
----------------------------------------------------------------------------------------------<br>
April 10, 1967<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-3D<br>
Improving Grid Drive On 20 Meters<br>
To improve the 14.0 MHZ grid drive add a 100 ohm 1/2 watt resistor<br>
between the two 10 meter coils on the driver grid side.<br>
----------------------------------------------------------------------------------------------<br>
February 16, 1973<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-1<br>
Carrier Null Control Failure<br>
Recently an improved mounting method was devised for the [PN 10-147]<br>
controls in kit models SB-102, SB-401 and HW-101. Current production<br>
utilizes a fiber washer for greater clearance and the case of the
control<br>
is grounded by a separate wire. We are anxious to know if this will<br>
reduce the failure rate. Please make note of any change, good or
bad,<br>
and keep us posted.<br>
----------------------------------------------------------------------------------------------<br>
January 29, 1974<br>
SB-401 Bulletin No:<br>
SSB Tranmitter SB-401-2<br>
Relay RL-2 Hang-up<br>
After a period of transmission, the relay remains in the transmit<br>
[energized] mode, rather than returning to the receive
[de-energized]<br>
mode.<br>
This problem is caused by gassy 6146 output amplifier tubes. When
these<br>
tubes become hot, there is enough secondary emission from the screen<br>
grids to keep RL-2 energized.<br>
The solution is to ground lug 7 of RL-1. This grounds the 6146
screen<br>
grids in receive, thus preventing the secondary emission current
flow<br>
from holding RL-2. The SB-401 manual will be revised to reflect this<br>
change in new production.<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Tranmitter SB-401-3<br>
Alignment of SB-301/SB-401 As Transceiver<br>
The following method of aligning the SB401 SSB Transmitter for use as
a<br>
transceiver with the SB-301 SSB recevier may be preferred by those
who<br>
are not familiar with the units.<br>
The SB-301 should be aligned according to the manual. Upon beginning<br>
alignment of the SB-401 the heterodyne oscillator crystals, LSB and
USB<br>
crystals should be removed from the SB-301 and installed in the
SB-401.<br>
[This step is not necessary if the SBA-401-1 accessory crystal pack
is<br>
installed]. Do not connect any cables between the two units. Proceed<br>
with alignment as given on page 97 of the SB-401 manual.<br>
Upon completion of the alignment, remove the crystals and reinstall
in<br>
the SB-301. Connect all cables and set LMO switch to locked position
and<br>
funtion switch to transceive on SB-401. The receiver heterodyne<br>
oscillators may need to be retouched for maximum drive to the
transmitter<br>
finals, in some cases going to the top peak on the coils.<br>
The receiver BFO coil will also have to be adjusted. The voltage may
be<br>
measured during adjustment at the 50 MFD capacitor, C127, just to
the<br>
right of V2 on the carrier generator board in the SB-401. This will<br>
eliminate the need for taking the trasmitter out of the cabinet and<br>
tipping on its side.<br>
The two units are then ready for transceiver operation.<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-4<br>
Spotting With The SB-301 & SB-401<br>
In using the SB-301 SSB receiver and SB-401 SSB transmitter in<br>
independent operation with all cables connected, some difficulty has
been<br>
experienced in spotting in the single sideband mode. This has been
in<br>
the form of feedback, inability to zero beat a station, etc.<br>
The feedback problem can be reduced or eliminated by dressing the
red<br>
wire between the receiver antenna jack and lug 3 of the antenna
relay<br>
away from the final amplifier tube sockets. If feedback is still<br>
excessive, the red wire may be replaced by coax with the shield
connected<br>
to the ground lug on the receiver antenna jack.<br>
The accepted method of zero-beathing a SSB station is to "talk"
yourself<br>
in on frequency. Tune in the signal for maximum intelligibility,
then<br>
with the function switch in spot, "talk" yourself in on
frequency until<br>
you can also understand your voice. With this method the transmitter
is<br>
exactly on frequency.<br>
You may wish to use a pair of headphones while talking yourself in
on<br>
frequency.<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-5<br>
CW Sidetone With Headphones<br>
The attached pictorial shows a simple change of interconnecting cables
on<br>
the SB-401, SB-303 or SB-301 which will allow CW sidetone of the
SB-401<br>
to be heard on headphones while defeating the speaker.<br>
SB401 & SB-301<br>
With this combination, make the cable changes shown and then just
plug<br>
your headphones into the headphone jack. The speaker will
automatically<br>
be cut off with headphones plugged in.<br>
SB-401 & SB-303<br>
With this combination, make the cable changes as shown and then plug
your<br>
headphones into the headphone jack. The difference here is that you
must<br>
pull the speaker disable switch on the front panel of the SB-303 to
mute<br>
the sidetone fromthe speaker.<br>
((Sorry, but even with magnifying glass I cannot read the
connections<br>
shown on the backs of the examples. Also, the rear of the 401 &
301<br>
isn't like the ones I have sitting here? [But then, my manuals are
dated<br>
1966!] )<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-6<br>
SB-401 RF Voltage Service Guide<br>
On the attached schematic we have indicated RF voltages as measured in
an<br>
SB-401 in the 80-meter CW key down condition. RF voltages are
provided<br>
at the grid and plate of each stage so that it can be determined if
the<br>
problem is in the grid or plate circuit of the stage.<br>
An 11 megohm input VTVM and Heath 309C RF probe was used to make the<br>
measurements.<br>
The voltages will vary from transmitter to transmitter and should be<br>
expected. Crystal oscillator voltages will vary considerable.<br>
This procedure traces the RF signal voltage from stage to stage. It
is<br>
an easy method to isolate a problem stage so that steps can be taken
to<br>
correct the trouble.<br>
We suggest starting at the carrier generator and working trough to
the<br>
final, as each stage is dependent on the previous stage.<br>
Trace the RF up to the point it is lost, then back up one stage.
Should<br>
one or two bands be operating properly and the rest have difficulty,
make<br>
reference RF voltage measurements on one of the operating bands and
make<br>
comparison measurements on the inopeative bands. In this way the
stage<br>
causing difficulty is quickly isolated.<br>
Once the stage is isolated steps can be taken to correct the
problem.<br>
Check for wiring errors, intermittent solder connections, loose
hardware<br>
and bent switch contacts.<br>
((NOTE: Voltages shown on the schematic were:<br>
1.5V [Pin 2 of V9]<br>
36V [Pin 6 of V9]<br>
36V [Pin 5 of V10] ))<br>
Voltages taken on 80 M. 260 mils plate current<br>
125 watts output on HM-102 Level control at 10:30<br>
position<br>
.5 mils grid current Measurements taken in<br>
tune<br>
position with exception of one at<br>
V5 (USB)<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-7<br>
SB-400 / SB-401 CW VOX Troubleshooting Guide<br>
It is assumed that the basic steps such as making DC voltage<br>
measurements, checking the tubes and reviewing the soldering, have
been<br>
completed.<br>
The following information was compiled using SB-400 and SB-401<br>
transmitters in the 80M CW key down condition.<br>
The AC signal voltages have been measured with a VTVM throughout the
CW<br>
Vox circuit and are as follows. Note: The voltages may vary some
from<br>
transmitter to transmitter.<br>
SB-400 SB-401<br>
Pin 11 of V13 .5VAC .5VAC<br>
Pin 9 of V13 25VAC 20VAC<br>
Pin 9 of V12 1.6VAC 1.2VAC<br>
Pin 10 of V12 90VAC 70VAC<br>
Pin 11 of V12 1.7VAC 1.5VAC<br>
Pin 2 of V12 45VAC 45VAC<br>
Pin 7 of V12 18VDC 21VDC<br>
By tracing the AC signal from stage to stage the point of trouble can
be<br>
isolated and steps taken to correct it.<br>
Check for bias removal at pin 9 of V12 when the key is closed. If
the<br>
bias voltage is not removed check the wiring of FIR LUGS 11 ans 12.
Also<br>
check for continuity from the key jack to R127 through FIR.<br>
A change in VOX delay after operating for a period of time can be
caused<br>
by leakage in diode [SB-400 D-2] [SB-401 D105]. The other
possibility<br>
is a change in value of capacitor [SB-400 C123] [SB-401 C141].
Either<br>
component could experience a change in operating characteristics due
to<br>
heat. In such a case mount the two parts on the bottom of the
circuit<br>
board to correct this condition.<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-8<br>
Alternate Tune-up Procedure For SB-401<br>
Before proceeding, review and understand the description for each of
the<br>
controls indicated in figure 1-2, fold-out from page 86.<br>
Preset controls as follows:<br>
Function Switch TRCV or TRAN<br>
Mode Switch CW<br>
Band Switch Desired band<br>
Meter Switch Rel PWR<br>
Level Control Full CCW<br>
Freq Control Locked or Unlocked<br>
Final Load 50 Ohm Mark<br>
Final Tune Desired Band<br>
Driver Tune First Mark from full CCW<br>
Main Tuning To desired frequency<br>
NOTE:<br>
If the SB-401 is used with a receiver other than the Heathkits SB-300
or<br>
SB-301 the function switch should be at [TRANS] and the freq control
at<br>
unlocked.<br>
NOTE:<br>
The key should be closed during and opened after each step, unless<br>
otherwise stated.<br>
***DO NOT HOLD THE TRANSMITTER IN A KEY DOWN CONDITION IN EXCESS OF<br>
30<br>
SECONDS OR DAMAGE COULD RESULT TO THE FINAL AMPLIFIER TUBES.***<br>
1. Plug the key in the keyjack.<br>
2. Advance the level control to 12:00 o'clock.<br>
3. Close the key and peak the meter for maximum REL PWR with the
final<br>
tune control.<br>
4. Peak the driver tune control for maximum REL PWR indication.<br>
5. Peak the final load control for maximum REL PWR indication.<br>
6. Repeat steps 3, 4, 5<br>
7. Turn the meter swtich to Grid; DO NOT CLOSE KEY.<br>
8. Close the key and check the grid current. If in excess of half<br>
scale, turn the level control counter clockwise to bring the meter<br>
reading to half scale or less. If less than half scale but above zero
do<br>
not adjust.<br>
9. Tune the meter switch to plate; DO NOT CLOSE KEY.<br>
10. Close the key and check the plate current, It should be between
200<br>
and 240 MA.<br>
11. Repeat steps 3, 4 and 5 with meter in the REL PWR position.<br>
12. The transmitter is now fully loaded and ready for CW operation.<br>
13. For SSB operation set the mode switch to the desired SSB mode.<br>
14. During SSB operation turn the meter switch to the ALC positon.<br>
Adjust the mike level control for proper ALC indication as indicated
on<br>
page 108 of the manual.<br>
15. Antennas which resonate to the transmitting frequency, presenting
a<br>
low SWR and an impedance of 50 ohms, should be used.<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-9<br>
SB-401 Instability and Corrective Information<br>
***We suggest you check for each of the following possible causes***<br>
1. Intermittent, rosin or cold solder joints.<br>
2. Loose hardware at tube sockets, terminal strip, circuit boards
and<br>
shields.<br>
3. Poor lead dress at V5, V8, V9, V10 and V11. The component leads
must<br>
be as short as possible, while dressing the part down against the<br>
chassis.<br>
4. Check RFC 4 and RFC 6 to be sure they are not interchanged.<br>
5. Coil leads to the band switch should be as short as possible.<br>
6. Check all edges of the final enclosure for proper grounding to
the<br>
main chassis.<br>
7. Check C26 [Final tune capacitor] to be sure it is isolated from
its<br>
turning shaft. This is to prevent RF from traveling on the shaft to<br>
the front panel.<br>
8. Check for good contact of the ground clip to the coil box.<br>
9. Be sure the shield plates are properly installed in the coil box.<br>
10. A 100 Ohm 1/2 W resistor should be installed between lugs 1 of
coils<br>
CM and CN. This replaces a short length of buss wire between the<br>
two coils.<br>
11. The leads for capacitor TA should be down on the chassis not run<br>
through the air.<br>
12. If the SB-401 is being used with the SB-300 or SB-301 in the<br>
transceive mode the accessory crystal pack should not be<br>
installed in the SB-401.<br>
13. Change the driver and final tubes then reneutralize per manual<br>
instructions.<br>
14. Improper adjustment ofthe Het OSC coils could cause improper
mixing<br>
action, resulting in the final operating at a different frequency,<br>
appearing as instability.<br>
15. Check for a good ground between the front panel and chassis.<br>
16. Check the SWR of the antenna system at frequency of operation.<br>
17. Check the COAX for leakage.<br>
18. Is the trasmitter properly grounded?<br>
19. Realign using a properly terminated 50 Ohm not-reactive dummy
load.<br>
[[[NOTE: THIS DOES NOT INCLUDE A LIGHT BULB]]].<br>
20. Be sure all shield and tube shields are installed.<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-10<br>
SB-400 & SB-401 Hum Troubleshooting Guide<br>
1. Disconnect one lead of the low voltage filter choke and measure
its<br>
resistance. Its normal resistance is 120-140 ohms. If the<br>
resistance is below 100 ohms the choke is shorted and should be<br>
replaced.<br>
2. Check the following capacitors for leakage:<br>
SB-400 SB-401<br>
C180 C183 C78 C403<br>
C181 C184 C79 C404<br>
C179 C147 C81 C402<br>
C182A C185 C77A C106<br>
C182B C77B<br>
3. Check terminal strip and terminal board grounds.<br>
4. Retighten hardware at tube sockets, terminal strips, circuit
boards<br>
and shields.<br>
5. Check the tubes for heater to cathode leakage.<br>
6. Check the grounds for the shield lead of each length of shield
cable.<br>
7. Recheck all solder connections. Be sure that the [C79 SB-401],
[C181<br>
SB-400] mounting lug is securely soldered to the metallic mounting<br>
wafer.<br>
----------------------------------------------------------------------------------------------<br>
May 23, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-11<br>
SB-400 & SB-401 Driver Stage Troubleshooting Guide<br>
It is assumed that the basic steps such as making DC voltage<br>
measurements, checking tubes and reviewing soldering have been
completed.<br>
Normal drive to the grid of the 6CL6 is 1.5-2.5V RF on all bands. In<br>
some cases it will be higher.<br>
1. Check to see if the blocking bias is being removed from pin 2 of
the<br>
tube during the key down or tune conditions. The bias is about -15VDC
in<br>
a key up condition; in the key down condition it is about -.5VDC.<br>
2. Check the cathode resistor to be sure it is of the correct value<br>
[SB-401 -- 150 ohms], [SB-400 -- 100 ohms] and correctly installed.<br>
3. Check the wiring of [SB-400 - C90, A, B, C, D], [SB-401 - C4, A,
B,<br>
C, D], to bandswitch decks BS3R and BS4R. If two of the sections are<br>
interchanged, peaking of the coils will be incorrect and very low
drive<br>
will be present.<br>
4. Incorrect adjustment of the 8MHZ trap can cause suck out on one
or<br>
more bands. To adjust the trap correctly complete the outlined steps
in<br>
the manual.<br>
5. Check the screen and plate voltages for the 6CL6 in the key down<br>
position. If 50V or better low, check the following components:
SB-400;<br>
R-93, R-94, RFC-92, C-164, C-97 AND C-99. SB-401; R-4, R-5, RFC-4,
C-8,<br>
C-7 AND C-58.<br>
6. The capacitors mounted on the driver coils should have as short
leads<br>
as practical. All leads from the coils to the andswitch should not
be<br>
any longer than necessary.<br>
7. Bypass capacitors shold have short leads and be placed as close
as<br>
practical to the chassis.<br>
8. Check the ground of the shield for the shielded cable used in the<br>
plate circuit of the 6CL6.<br>
9. Check the value of [SB-40 R-94] [SB-401 R-5]. The value should be<br>
6.8K and 1W. This resistor determines the drive to the final
amplifier<br>
stage. This is accomplished due to the RF voltage drop across the<br>
resistor.<br>
10. Retighten hardware at the tube sockets, terminal strips and
shields.<br>
----------------------------------------------------------------------------------------------<br>
July 24, 1974<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-12<br>
Incorrect Resistance Reading at Terminal Strip AC<br>
Refer to manual # 595-947-07, Page 88. The resistance readings at lugs
2<br>
and 4 of terminal strip AC will be zero, since the addition of the
ground<br>
wire to lug 7 of the main relay RL-1.<br>
----------------------------------------------------------------------------------------------<br>
July 24, 1978<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-13<br>
LMO Drift, Intermittent Frequency Shift<br>
Check for a dirty or corroded phono connector on the rear of the
LMO.<br>
CLean if necessary.<br>
----------------------------------------------------------------------------------------------<br>
August 7, 1978<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-14<br>
Loading Capacitor Turns as Plate Capacitor is Rotated<br>
This problem can be caused by:<br>
- Insufficient friction in the loading capacitor or;<br>
- Excessive friction between the plate and load tuning shafts.<br>
If the problem persists after freeing and lubricating the shafts,
install<br>
a rubber grommet [PN 73-3] on the loading capacitor shaft between
the<br>
pulley and the RF cage. Apply slight pressure to the grommet as the<br>
pulley set-screw is tightened. This will add enough friction to keep
the<br>
loading capacitor still while tuning the plate control. Use only as<br>
needed.<br>
----------------------------------------------------------------------------------------------<br>
January 21, 1980<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-15<br>
Driver Plate Resistor Overheats<br>
+ + + + Information not yet available + + + +<br>
----------------------------------------------------------------------------------------------<br>
March 7, 1980<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-16<br>
Will Not Work With HDP-1220 BW Clipper<br>
+ + + + Information not yet available + + + +<br>
----------------------------------------------------------------------------------------------<br>
April 10, 1980<br>
SB-401 Bulletin No:<br>
SSB Transmitter SB-401-14<br>
Germanium Diode Change<br>
+ + + + Information not yet available + + + +<br>
----------------------------------------------------------------------------------------------<br>
That is all I presently have for the SB-401 [1966-89]. Enjoy!<br>
73 de Joe W7LPF/4 [NNN0KUU]<br>
QWCA - SOWP - NCVA - FISTS - RCC<br>
Gordonsville, Va 22942 [Orange Co]<br><br>
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