Heathkit Service Bulletins - General (Revised/Complete)
Joseph W Lutz
joelutz at JUNO.COM
Fri Nov 7 20:57:46 EST 1997
July 10, 1968
Instability -- Trouble
shooting
Amateur Products
Bulletin No.
SB101, 100, HW100
GH-1
We suggest you check for each of the following possible causes:
1. Intermittent, rosin or cold solder joints.
2. Loose hardware at the tube sockets, terminal strips, circuit boards,
shields and rear panel sockets.
3. Poor lead dress at tube sockets V8 & V9. The component leads must be
short as possible.
4. Check C925 (Final tune capacitor) to be sure it is isolated from the
tuning shaft. This is to prevent RF from traveling on the shaft to the
front panel.
5. Check all edges of the final enclosures for proper grounding to the
main chassis.
6. Check the hardware for the side rails to be sure a good ground is
being provided.
7. Be sure that all the ground clips on the coil cover are making good
contact with the switch shields.
8. Check the soldering of the switch shields to the center pins of tube
sockets V6, V7, V10 & V11.
9. Check the ground leads from the switch board & shields, to be sure
they are going to ground foil & not to the preselector capacitor foil
pods on the RF driver board.
10. Check for broken or shorted pigtails on each of the shielded cables
in the unit.
11. Check RFC801 & L901 for any signs of deterioration or physical
damage, (burn spots). If apparent replace the part.
12. Improper adjustment of the Het. Osc. coils could cause improper
mixing action, resulting in the final operating at a different frequency
appearing as instability.
13. Change driver & final tubes then reneutralize per manual
instructions.
14. Check driver tube shield to be sure that it has a good ground
contact with the socket spring clip.
15. Check for a good ground between the front panel & chassis.
16. Check the SWR of the antenna system at the frequency of opertion.
Should be below 2:1.
17. Check the antenna coax for leakage, poor connectors & broken shield
connections.
18. Is the transmitter properly grounded?
19. Be sure all shields & tube shields are installed.
20. Realign using a properly terminated 50 ohm non-reactive dummy load.
NOTE: This does not include a light bulb.
21. Check for normal Het. Osc. test-point voltage.
22. Check for proper LMO injection voltage 1.0-1.5 VRF.
23. Check for a high AC ripple content in the LV-B+, HV-B+ and bias
voltages from the power supply.
24. Check to be sure that the shafts do not touch each other in the
insulated coupling, and that the set screws do not touch the PA shield.
25. Check to be sure that the PA tune shaft turns the variable capacitor
& is not slipping in the insulated coupling.
--------------------------------------------------------------------------------------------------------------------
August 20,
1968
Audio Amplifier & VOX Circuit
Troubleshooting
Guide
Amateur Products
Bulletin No.
SB & HW Tube Type Transceivers GH-2
It is assumed that the basic steps such as making DC voltage measurement,
checking tubes and 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
position.
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 set for .1V at 1KHZ
can be used as the signal source:
MIKE CONNECTOR LUG 1 .1 VAC
PIN 2 OF V1 .02 VAC
PIN 6 OF V1 10-15 VAC
LUG 4 LEVEL CONTROL 10-15 VAC
LUG 5 LEVEL CONTROL .5 VAC
PIN 9 OF V1 .2 VAC
PIN 8 OF V1 .1-.3 VAC
CENTER ARM OF VOX SENSITIVITY CONTROL 5-15 VAC
PIN 7 OF V17 5-10 VAC
PIN 6 OF V17 40-50 VAC
JUNCTION OF C211-D201 40-50 VAC
PIN 9 OF V12 9-15 VAC
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 possible open or poorly grounded
shield.
- Check for continuity through each of the shielded cables.
- Check for a proper ground at the mike level control.
If the frequency response of the audio stage is not within specifications
check the value and 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
operational characteristics due to heat.
--------------------------------------------------------------------------------------------------------------------
July 7, 1969
Relay Chatter
Amateur Products
Bulletin No.
SB-101, HW-100 GH-3
Prevention of relay chatter can be accomplished by bypassing RF to ground
in VOX circuit. This RF is picked up by mike cables, etc. Install a
.001mfd disc capacitor (Part No. 21-14) at hole 8 to adjancent ground
foil on bottom of the bandpass circuit board. This point has two
red-red-white wires connected to it also.
--------------------------------------------------------------------------------------------------------------------
October 29, 1970
Amateur Products Bulletin No:
GH-4
SBM-102-1
The attached modification instructions should be followed to correct the
driver preselector problem of peaking at a different location on receive
then transmit. This is caused by the tube miller effects as explained in
the modification sheet.
This should be installed on all units above when serviceing. SB-102 with
run numbers of 5446 and above should already contain the modification.
INTRODUCTION
This modification kit applies to the following Heath Transceivers:
1. All models HW-100, SB-100, SB-101 AND SB-101W.
2. Any model SB-102 that has a number lower than 5446 as the last four
digits of the series number [on the Blue and White Label].
The plate tank circuit of V6, the second transmitter mixer, is used in
the receive mode as the plate circuit of V10, RF Amplifier. Due to tube
Miller effects, additional capacity is required when receiving to permit
the driver preselector to peak at the same dial setting in both transmit
and receive modes. This modification uses automatic diode switching to
add the required compensating capacity.
PARTS LIST
PART QUAN- DESCRIPTION
NO. TITY
------- --------- -------------------
1-26 1 100K OHM, 1/2 WATT RESISTOR
1-35 1 1M OHM, 1/2 WATT RESISTOR
21-33 1 3.3PF DISC CAPACITOR
56-56 1 1N4149 DIODE [CATHODE END MARKED WITH A BAND]
344-50 1 BLACK HOOKUP WIRE
391-34 1 BLUE & WHITE IDENTIFICATION LABEL
431-62 1 3-LUG TERMINAL STRIP
INSTRUCTION SHEET
SOLDER
[ ] Remove the cabinet from the transceiver and turn the chassis bottom
side up.
[ ] Remove the coil cover.
[ ] If you wish, temporarily remove the support rail which holds one
end of the
switch boards.
[ ] Refer to figure 1 and bend a small "foot" on the end of one lead of
the 100 K
Ohm resistor.
[ ] Coat the "foot" with a liberal amount of solder.
[ ] Solder the foot on the resistor lead directly to the foil at point
11 on the RF driver circuit board. NOTE: A white-red-red wire
[and possibly other components are already soldered to this foil.
[ ] Cut the leads of the 3.3pF disc capacitor to 5/8".
[ ] Bend a 1/8" foot on the end of one lead of the disc capacitor and
solder this foot directly to the foil on the RF driver circuit
board at point X as shown. Make sure the solder does not short
circuit the foil to the switch shield.
[ ] Connect the cathode [Banded] end of the 1N4149 Diode to lug 2 of
the 3-lug terminal Strip [S-1]. Connect the other lead to lug 1
Of the terminal strip [NS].
[ ] Connect the 1M ohm resistor from lug1 [NS] to lug 3 [NS] of the
terminal strip.
[ ] Coat the terminal strip foot with solder.
[ ] Refer to figure 4 and solder the 3-lug terminal strip directly to
the rear side [driver grid switch board side] of the front switch
shield. Follow the dimensions given. [[1" in from edge of shield
and 1/2" down from top of shield]].
[ ] Connect the free lead of the 3.3 pF disc capacitor to lug 1 of the
terminal strip [NS].
[ ] Connect the free end of the 100K ohm resistor to lug 1 of the
terminal strip [S-4]. Make sure the capacitor and resistor leads
do not touch any other wires or components.
[ ] Prepare a 16" black hookup wire by removing 1/4" of insulation from
each end of the wire.
[ ] Connect one end of the black hookup wire to lug 3 of the termianl
strip [S-2].
[ ] NOTE: Two sets of steps follow. Use only those steps applying to
your transceiver.
Models with "SB-" prefix:
[ ] Refer to figure 5 and route the black hookup wire over the
bandswitch shaft, down through grommet CD, and back along the
wiring harness to lug 1 of the Bias Adjust control. Position the
wire against the switch shield.
[ ] Melt the solder on lug 1 of the Bias Adjust control and push the
bare end of the black hookup wire through the opening in the lug.
After the solder has cooled, tug on the wire to make sure it is
securely connected.
Proceed to the "Final Assembly."
MODEL HW-100:
[ ] Refer to figure 6 and route the hookup wire over the switch shaft,
through grommet CD, and along the wiring harness to Bias control
CT.
[ ] Melt the folder on lug 1 of control CT and pust the bare end of the
hookup wire through the opening in the lug. After the solder has
cooled, tug on the wire to make sure it is securely connected.
Final Assembly
NOTE: You can secure the hookup wire to the wiring harness with
electrical tape or with short pieces of hookup wire.
[ ] If it was removed, replace the support rail and secure it with the
hardware previously removed. Make sure all switch boards and
shields fit into the proper slots in the comb on the support rail.
[ ] Replace the coil cover. Make sure the grounding clips on the under
side of the cover fit over the switch shields.
[ ] Refer to the alignment section of your assembly manual and peak the
driver grid and driver plate coils..
[ ] Replace the transceiver cabinet.
[ ] Carefully peel away the backing paper from the blue and white
identification label. Then press the label onto the rear of
the cabinet. Be sure to refer to the numbers on this label in any
communications you have with the Heath Company about this kit.
Circuit Description
A negative voltage is always applied to the anode of D-907 from the Bias
Adjust control through resistor R-954. When receiving, a higher positive
voltage is applied to the anode of D-907 from the screen circuit of V11
through resistor R-955. As its anode is now positive, the diode conducts
and acts as a closed switch to supply a ground to C-955. This action
places the capacitor in parallel with C-421B and adds capacity to the
plate tuned circuit.
In the transmit mode, the positive voltage is removed by the opening of
contacts 3 and 11 of RL2. The remaining negative voltage prevents D-907
from conducting and it consequently acts as an open switch, removing the
ground from C-955. The capacitance of C-955 is therefore removed from
the plate circuit of V6.
------------------------------------------------------------------------------------------------------------------
The fiche index also lists GH-5 & 6. Cannot find 5, and #6 shows the
different type of power connects used [i.e., the 8 and 11 pin
male/female sockets, etc.].
------------------------------------
73 de Joe W7LPF/4 [NNN0KUU]
QWCA - SOWP - NCVA - FISTS - RCC
Gordonsville, Va 22942 [Orange Co]
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