HEATHKIT SERVICE BULLETINS-CONT.
Joseph W Lutz
joelutz at JUNO.COM
Thu Jun 12 23:55:27 EDT 1997
Hi Group[s],
To continue on the SB thread:
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May 23, 1974
SB-100
Bulletin No:
SSB Transceiver
SB-100-3
SB & HW Series Audio Preamplifier &
VOX
Circuit Trouble Shooting
Guide
It is assumed that the basic steps such as making DC voltage measurement,
checking tubes & reviewing the soldering have been completed.
The following information was compiled from the above transceivers in the
80M LSB position. The mike level control was at the 9:00 o'clock
poisition.
AC signal voltages are listed below. These voltages were measured from
the microphone connector through the VOX circuit. All measurements were
made with a VTVM. A microphone or audio generator for .1V @ 1KHZ can be
used as the signal source.
Mike Connector Lug 1
.1VAC
Pin 2 of V1 .02VAC
Pin 6 of V1 10-15VAC
Pin 6 Level Control 10-15VAC
Pin 5 Level Control .5VAC
Pin 9 of V1 .2VAC
Pin 8 of V1 .1 - .3VAC
Center Arm of VOX Sensitivity Control 5-15VAC
Pin 7 of V17 5-10VAC
Pin 6 of V17 40-50VAC
Junction of C211-D201 40-50VAC
Pin 9 of V12 9-15VAC
By tracing the AC signal from stage to stage the point of trouble can be
isolated & steps taken to correct it.
POSSIBLE TROUBLE AREAS
- Check each of the shielded cables for a possible open or poorly
grounded shield.
- Check for continuity through each of the shielded cables.
- Check for a proper ground at the mike control level.
- If the frequency response of the audio stage is not within
specifications check the values & installation of C1, C2, C3 & C9.
- A change in VOX delay after operating for a period of time can be
caused by leakage in diode D201. The other possibility is a change in
value of capacitor C213. Either component could experience a change in
operation characteristics due to heat.
-----------------------------------------------------------------------------------------------------------------
May 23, 1974
SB-100 Bulletin No:
SSB Transceiver SB-100-4
Instability - Trouble
Shooting
SEE BULLETIN NO: GH-1 DATED JULY 10, 1968
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December 18,
1974
SB-100 Bulletin No:
SSB Transceiver SB-100-5
Oscillations or
Low Drive
Loose boards cause sporatic self oscillations & unstable RF conditions,
particularly at the high [15 & 10 meter] bands. The comb brackets which
ahve been used are aluminum & could not be soldered. Steel brackets are
now available [Part No: 204-2096] & should be used whenever encountered
in the field. Both the switch shields & the driver boards should be
soldered to these brackets.
This change helps to increase grid drive as well as increase stability.
------------------------------------------------------------------------------------------------------------------
May 2, 1975
SB-100 Bulletin No:
SSB Transceiver SB-100-6
Self Oscillations Occurring After
Installation
of Steel Comb Brackets.
It has been found that in a number of units, self oscillations are still
occurring after installation of both settl comb brackets [Part No:
204-2096]. To correct the condition, the screws around the RF driver
board must be tightened securely. Also, the lockwarsers between the
circuit board & chassis must be installed, otherwise a good ground is not
assured. Retightening screws which are already snug will also cause
these oscillations to disappear in units where it is a problem.
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June 12, 1967
SB-101 Bulletin No:
SSB Transceiver SB-101-1D
Driver Oscillates on 40 Meters
Remove C-924 [.02 disc capacitor] from across 150K ohm resistor & delete
from circuit.
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November 1, 1967
SB-101 Bulletin No:
SSB Transceiver SB-101-2D
Switch Action
Improvement
DELETE: (2) 253-67 (2) WASHER, .186OD, .054 THICK (1 EA FOR 100-445)
ADD: (2) C253-67(1) " " " " "
(FOR 100-445)
ADD: (2) B255-79(1)SPACER, 1/8 SHOULDER, THREADED
ADD: (2) A263-7 (1)FOOT, FELT, 1/8" THICK
DELETE:(4) 266-91 (1)ACTUATOR, SLIDE SWITCH
ADD: (4) 266-97 (1) " " " "
-----------------------------------------------------------------------------------------------------------------
NOVEMBER 1, 1967
SB-101 Bulletin No:
SSB Transceiver SB-101-3D
Improper Tuning
SEE BULLETIN NO. HW-100-1D DATED NOVEMBER 1, 1967.
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APRIL 18, 1968
SB-101 Bulletin No:
SSB Transceiver SB-101-4D
Improper Tuning
on 40 Meters
Description of Change:
DELETE: (2) B21-31 (50) CAPACITOR, DISC .02 MFD Z5U
ADD : (2) B21-31 (49) " " "
" "
DELETE: (4) 85-131-1 (1) PC BOARD, RF DRIVER MIXER
ADD : (4) 85-131-1 (1) " " "
"
REMOVE: C-424 installed across R-401
NOTE: SBM-100-1 called for the installation of this capacitor on SB-100
units. This capacitor should now be removed.
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June 3, 1968
SB-101 Bulletin No:
SSB Tranceiver SB-101-5D
Grounding Problems on
Tranceivers
A quality of factory wired transceivers have been shipped with loose
rivets both at the rear phono sockets & at the final tube sockets.
This is causing a serious grounding problem. Corrective recommendations
are shown on the attached sheet:
[[[[[[[[[[[[[NOTE: IF MY INTERPRETATION IS NOT CLEAR - PSE LET ME
KNOW]]]]]]]]]
Illustration shows the installation of a ground buss for the rear panel
phono sockets. It also states that if the final tube socket rivets are
loose, they should be drilled out & eplaced with 6-32 hardware.
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Okay gang - that takes care of it for tonite - have to spend some
quality time with my bride. Will resume with Bulletin SB-101-1. Ciao!
73 de JOE
- - - - - - - - - - -W7LPF/4 (NNN0KUU)- - - - - - - - - - - - - - -
QWCA - NCVA - SOWP - FISTS
Gordonsville, Va 22942 (Orange County)
Looking for: Heathkit HR/HX-20, MR/MT-1,
Collins 516F-2, 312B-4, EFJ TR Switch
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