Heathkit Service Bulletins - SB2XX Series (Complete)
Joseph W Lutz
joelutz at JUNO.COM
Mon Aug 18 00:12:38 EDT 1997
January 22, 1976
SB-200 Bulletin No:
1 KW Linear Amplifier SB-200-1
Meter Switch Lugs Shorting To Bottom Cover
The meter switch supplied in the kit may have long lugs on the switch,
which can result in shorting of lugs 6 and 7 of the switch to the bottom
cover. Shorting lug 6 of the switch to the bottom cover will cause the
antenna relay to close when the meter switch is in the "grid" position,
and release in the "plate" position.
Shorting of lug 7 to the bottom cover will cause antenna relay closure in
any position of the meter switch.
These switch lugs should be bent to prevent shorting.
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February 3, 1976
SB-200 Bulletin No:
1 KW Linear Amplifier SB-200-2
Replacement Fan Blades
The PN 266-21 fan blade is no longer available. The PN 266-900 blade
will be used as a replacement. When using the new blade, the set screw
must also be changed.
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May 15, 1979
SB-200 Bulletin No:
1 KW Linear Amplifier SB-200-4
Sheet Metal Screws Will Not Tighten
If the perforated covers will not secure properly due to enlarged sheet
metal holes, install a 6-32 speednut [PN 252-22] over the lip and
surrounding hold. The 6-32 X 3/8" sheet metal screw [PN 250-8] will then
tighten securely.
Using the speednuts does not noticeable degrade the products' shielding
capabilities.
-----------------------------------------------------------------------------------------------------------------
May 15, 1979
SB-201 Bulletin No:
Linear Amplifier SB-201-1
Sheet Metal Screws Will Not Tighten
See Bulletin No: SB-200-4 Dated May 15, 1979.
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January 26, 1970
SB-220 Bulletin No:
2 KW Linear Amplifier SB-220-1
SBM-220-1 Modification Kit
A few model SB-220 Linear Amplifier owners may encounter some unusual
operating conditions, usually in RTTY service, which cause the zener
diode [PN 56-75] in the bias supply to fail. This failure is evidenced
by an idling plate current of around .3 amperes instead of the normal .09
to .12 amperes. The following step-by-step instructions are for
replacement of this part with a 10-watt zener diode.
Parts List
Part No: Parts per kit Description
56-82 1 1N3996A Zener Diode, 5.1
volt, 10 watt,
with mounting hardware
344-2 1 length of black stranded
wire
352-13 1 silicone grease pod
597-503 1 Instruction sheet
Step-By-Step Assembly
References to a "page" are to the Model SB-220 Assembly Manual dated
11-28-69.
Note: [S-] with a number, such as [S-3], means to solder the connection.
The number tells how many wires are at the connection.
[ ] Refer to pictorial 4-20 [Fold-out from page 56] in your SB-220
Assembly Manual and remove the amplifier from its cabinet. Be sure to
place a book under the amplifier.
[ ] Remove the top rear plate cover and the perforated top cover from
the amplifier. Do not remove the screw from the phenolic spacer on the
under side of the top cover.
[ ] Unsolder, remove and discard the zener diode and its two heat sinks
from the circuit board. Clear the solder from the two holes from which
the zener diode leads were removed.
[ ] Refer to figure 1 and make a cut in the fish paper along the edge
of the capacitor bank bracket for at least a distance of 1 3/4" down from
the top edge of the paper. Make another cut horizontally to the left
[front] edge of the paper.
[ ] Remove the fish paper outlined by the cuts. Use a screwdriver, or
similar object, to scrape clean the area around the hole in the RF shield
exposed by the removed fish paper.
[ ] Remove the solder lug from the zener diode package. Bend up the
end of the lug having the smaller hole [90 deg right angle].
WARNING: When you handle silicone grease in the following steps, make
sure you do not get any in your eyes.
[ ] Cut the side of the silicone grease pod with a knife point so the
grease can be squeezed out.
[ ] Remove the two mica washers from the zener diode package. Squeeze
some silicone grease out of the pod and, with your finger, liberally coat
both sides of each mica washer with the grease.
[ ] Refer to figure 2 and mount the zener diode. Make sure the nylon
bushing surrounds the threaded stud of the diode as it passes through the
RF shield and that the two mica washers are mounted against each side of
the RF shiled. Position the solder lug [with the attached wire] so it
points down toward the chassis. Thighten the hardware snugly, but do not
overtighten.
[ ] Use an ohmmeter to make sure there is infinity reading between the
body of the zener diode and the RF shield. If only a fraction of an ohm
resistance is obtained, the body of the diode [or the solder lug] is
probably touching the RF shield. Bend the solder lug to clear the RF
shield, or remove and reinstall the diode as necessary.
[ ] From the foil side of the circuit board, push the end of the 3"
wsire coming from the solder lug into the lower of the two holes vacated
by the removed zener diode [S-1]. This hole is screened on the other
side of the circuit board for the banded end of the diode.
[ ] Connect one end of the remaining 3" wire to the terminal extending
from the center of the new zener diode [S-1]. Push the other end of this
wire into the upper zener diode hole in the circuit board[S-1].
[ ] Trim off any excess wire lengths from the diode holes on the
component side of the circuit board.
[ ] Carefully inspect the zener diode to make sure that it does not
tough any metal other than the mounting hardware and the two connecting
wires. The capacitor bracket may be bent slightly toward the rear panel,
if necessary.
[ ] Replace the top rear cover and the perforated top cover on the
amplifier. Use the sheet metal screws previously removed.
[ ] Refer to page 64 and replace the amplifier in its cabinet.
This completes the installation of the 10-watt zener diode.
TEST
1. Reinstall the ampliefier in your station.
2. Place the mode switch at CW/TUNE and turn the amplifier on.
3. Turn the exciter MIC/CW level fully counterclockwise.
4. Turn the exciter to tune to close the amplifier antenna relay.
5. The plate meter should read from .09 to .12 amperes.
------------------------------------------------------------------------------------------------------------------
February 11, 1971
SB-220 Bulletin No:
2KW Linear Amplifier SB-220-2
Arcing on Circuit
Board
Under certain conditions it is possible arcing will occur between D-7 and
D-14 outer foil pad and the adjacent metal spacer. A permanent change is
being made to an insulated spacer at these two locations. The other two
spacers must remain metal to provide grounding for the circuit board.
This change should be made on all units serviced to avoid future trouble.
Change: PN 225-71 Metal Spacer to PN 255-42 Phenolic Spacer
-------------------------------------------------------------------------------------------------------------------
April 18, 1972
SB-220 Bulletin No:
2 KW Amplifier SB-220-3
Quieter Fan Motor
This Bulletin is obsolete and replaced by Bulletin No: SB-220-4
--------------------------------------------------------------------------------------------------------------------
May 3, 1974
SB-220 Bulletin No:
2 KW Amplifier SB-220-4
Fan and Motor Replacement
When ordering fan motor, be sure to order by part number from -08 level
and above manuals. Fan motor [PN 420-86] and new fan blade [PN 266-296]
must be ordered together because previous fan blade will not fit new
motor. Follow the installation instructions given in most current manual.
--------------------------------------------------------------------------------------------------------------------
September 11, 1974
SB-220 Bulletin No:
2 KW Amplifier SB-220-5
Arcing Between Tuning Capacitor [C55} and Plate Coil Bracket
The spacing between the tuning capacitor [C55] and plate coil bracket has
decreased due to a change in shape of the tuning capacitor. The smaller
spacing has resulted in arcing between the bracket and capacitor. To
prevent this arcing, the following change is being made:
Change: Plate Coil Bracket
From: PN 204-1042 To: PN 204-2102
The 204-1042 type bracket can be used if 1/8" of metal is removed from
the gap of the bracket.
--------------------------------------------------------------------------------------------------------------------
September 18, 1974
SB-220 Bulletin No:
2KW Amplifier SB-220-6
Mounting "Temple" Brand Electrolytic
Capacitors
The "Temple" brand of 200UF electrolytic capacitors used in this kit have
a rim at the terminal end. Therefore, when capacitors of this type are
installed, it will be necessary tomount them so that the rim will
protrube from the capacitor mounting insulator.
--------------------------------------------------------------------------------------------------------------------
February 11, 1976
SB-220 Bulletin No:
2KW Amplifier SB-220-7
Front Panel Will Not Fit
Some 26-145 air variable capacitors were supplied with oversize mounting
feet. When installed, these capacitors will prevent the front panel from
fitting flush against the chassis sheet metal.
These capacitors should be replaced with PN 26-145 capacitors whose
mounting feet are not more that 1/2" long.
-------------------------------------------------------------------------------------------------------------------
March 24, 1976
SB-220 Bulletin No:
2KW Amplifier SB-220-8
Replacement Motor Mounting Hardware
Replacement fan motors in parts stock may not have the 8-32 mounting nuts
supplied. Use PN 252-4 nuts, or the old hardware if the nuts are not
supplied with the replacement part.
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May 20, 1976
SB-220 Bulletin No:
2KW Amplifier SB-220-9
Low Power Output or Open Filaments
Because of the high current flowing in the filament circuit of the 3-500Z
triode, any low resistance due to a poor solder connection can result in
relatively large voltage drops and heat being developed at the poor
solder connection. After some period of operation the output power of
the amplifier may begin to fall off, or the filament circuit may open.
In complaints of low power, check the filament circuit for solder joints
that look "cold", and resolder as necessary; a .012 ohm resistance will
result in over a 0.5V drop in filament voltage, with consequent losses in
filament emission.
In cases of open tube filaments, pull the tube and resolder the tube
filament pins, then recheck tube filament continuity. This may save a
customer the cost of a new 3-500Z.
--------------------------------------------------------------------------------------------------------------------
February 17, 1978
SB-220 Bulletin No:
2KW Amplifier SB-220-13
Quieter Fan Motor [PN 420-601]
A quieter fan motor is now available for this kit. This motor will
replace PN 420-86.
The necessary mounting hardware and an instruction sheet are included
with the PN 420-601 motor.
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April 14, 1978
SB-220 Bulletin No:
2KW Amplifier SB-220-14
Short Motor Leads
The leads of the fan motor [PN 420-601] currently being shipped are too
short to reach lug AW. The lead length is sufficient to reach lug 2 of
terminal strip AE.
When replacing the older motor [PN 420-86], unsolder one motor lead at
lug 2 at terminal strip AE. Clip the other motor lead [to lug AW] about
5 inches from motor. Install new motor and reconnect one lead to
terminal strip AE, lug 2.
Shorten remaining motor lead as necessary to connect to existing lead
going to lug AW. Use wire nut [PN 432-199] for the connection. Refer to
the excerpt from the manual insert [PN 591-2585].
------------------------------------------------------------------------------------------------------------------
April 17, 1978
SB-220 Bulletin No:
2KW Amplifier SB-220-15
Low Output Power on 10 Meters
Check for three [3] turns of wire, instead of four [4] turns, on the
parasitic suppressors, PC1 and PC2 [PN45-53].
If the coils have four [4] turns, they will be resonant at 10 meters,
causing low power output on this band. Replace the suppressor, or remove
one [1] turn as necessary.
Also, when loading on 10 meters, start with the load control at '4'.
--------------------------------------------------------------------------------------------------------------------
May 15, 1979
SB-220 Bulletin No:
2KW Amplifier SB-220-16
Sheet Metal Screws Will Not Tighten
See Bulletin No: SB-200-4 Dated May 15, 1979.
--------------------------------------------------------------------------------------------------------------
July 31, 1979
SB-220 Bulletin No:
2KW Amplifier SB-220-17
Ordering New Fan Motor [PN 420-601] or Tuning Capacitor
[PN 26-164]
When the customer needs a replacement motor or tuning capacitor for the
older motor [PN 420-86] or capacitor [PN 26-131], he must order using the
old part number in order to receive instructions and additional hardware
to mount these new parts.
------------------------------------------------------------------------------------------------------------------
July 31, 1979
SB-220 Bulletin No:
2KW Amplifier SB-220-18
Presetting of Load Control on 10 Meters
When tuning u on 10 meters, preset the load control to about 7-8. In
some units, full power output cannot be obtained at the '4' setting in
the tune-up procedure in the manual. Make the load control setting
correction to Bulletin No: SB-200-15.
------------------------------------------------------------------------------------------------------------------
July 31, 1979
SB-220 Bulletin No:
2KW Amplifier SB-220-19
Filament Transformers Keep Burning Out on 220 Volts
If the filament transformers keep buring out on 220 volts, and are okay
on 120 volts, check for an opern primary on the high-voltage transformer,
T1. Since all primaries are cross connected, this will cause high
current on one side of filament transformer, T2, primary, burning it out.
Isolate all primaries and ohm out.
------------------------------------------------------------------------------------------------------------------
November 28, 1978
SB-221 Bulletin No:
Linear Amplifier SB-221-1
New Tuning
Capacitor
A new tuning capacitor [PN 26-164] will be available after January of
1979. This capacitor has a higher breakdown voltage.
The first two productions will not have this capacitor. After the part
becomes available, the tuning capacitor, C55, should be replaced with the
new type only upon customer complaint of arc-over.
---------------------------------------------------------------------------------------------------------------
February 20, 1979
SB-221 Bulletin No:
Linear Amplifier SB-221-2
Tuning Capacitor Arc-over
A new tuning capacitor, C55 [PN 26-164] is now available which has a
higher breakdown voltage to prevent arc-over problems.
The first two productions will have a [PN 26-131] capacitor installed/
These tuning capacitors should be replaced with the new type if arc-over
is a problem.
The new tuning capacitor is about 1-1/2" longer than the older one, so it
is necessary to install a space at "DA" to permit proper mounting of the
plate coil. Install the space as shown in the pictorial. (((Spacer is
attaced to coil at the plate coil bracket))).
Parts required:
1 - 6-32 X 1/4" screw [PN 250-56]
1 - #6 lockwasher [PN 254-1]
1 - 6-32 X 1-1/2" tapped metal spacer [PN 255-129]
1 - capacitor [PN 26-164]
This bulletin supercedes SB-221-1 dated November 28, 1978.
--------------------------------------------------------------------------------------------------------------------
May 15, 1979
SB-221 Bulletin No:
Linear Amplifier SB-221-3
Sheet Metal Screws Will Not Tighten
See Bulletin No: SB-200-4 dated May 15, 1979.
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February 18, 1975
SB-230 Bulletin No:
Linear Amplifier SB-230-1
Power Reduction When Reactivated on 10 Meters
After the linear has been loaded up on 10 meters and allowed to cool for
three minutes, the power might only go up to 200 watts output when
reactivated. After a few seconds [A1 emission key down] the output will
jump up to a normal 550 watts.
Remove the wire from between the rf choke and coupling capacitor C11 and
connect a 14 guage bare wire between the solder lug on C11 and the solder
lug on top of the tube plate cap.
--------------------------------------------------------------------------------------------------------------------
August 15, 1975
SB-230 Bulletin No:
Linear Amplifier SB-230-2
New Type Delay Tube Socket
A newer type delay tube socket was just procured, using the same art
number [436-56], will have to be mounted from the bottom side of the
chassis, which is contrary to the manual instruction.
The manual will be inserted.
------------------------------------------------------------------------------------------------------------------
September 30, 1976
SB-230 Bulletin No:
Linear Amplifier SB-230-3
Replacig Grid Bypass Capacitors
Replacing gid bypass capacitors can be made much easier by following
these steps:
1. Remove the tube clamp.
2. Remove solder from the capacitor mounting hole, using a desoldering
tool.
3. Clip the old capacitor lead, and unscrew and remove the old
capacitor.
4. Clip a slot in the upper ring of the grid ring capacitor mounting
hole, and bend as shown below.
5. Follow the manual instructions for shaping the new capacitor.
6. Install the new capacitor in the chassis, secure in place, and put
the capacitor lead in the slot in the ring.
7. Bend ring back to shape and solder.
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September 30, 1976
SB-230 Bulletin No:
Linear Amplifier SB-230-4
Improperly Installed
Grid Ring
The grid ring on the #8873 power tube should be checked for proper
installation before power is applied to the linear.
The grid ring may be improperly installed on the ceramic portion of the
tube, and either touches the plate, or allows high voltage to arc over
and destroy the switching diode D17 across the relay. The power supply
diode stack and the PA tube itself, can be easily destroyed.
The grid ring should be installed low enough on the tube to prevent
touching or arching of the high voltage, but not so low that it touches
the metal rivets holding the tube socket.
----------------------------------------------------------------------------------------------------------------
October 18, 1976
SB-230 Bulletin No:
Linear Amplifier SB-230-5
6KV Coupling Capacitor Cannot Be Mounted On Tuning
Capacitor
The [PN 26-144] tuning capacitor has a 6-32 threaded shaft on the upper
left rear end [when viewed from the rear of the capacitor] used to mount
the .001 UF, 6KV [PN 21-165] output capacitor (Refer to P. 47, pictorial
15 of the assembly manual).
Some SB-230's have been shipped with the stud on the opposite side,
leading to incorrect installation of the 10 meter coil if customers
attempt to assemble the unit with the defective capacitor.
The defective [PN 26-144's] should be replaced with capacitors having the
stud on the correct side.
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September 26, 1978
SB-230 Bulletin No:
Linear Amplifier SB-230-6
Meter Scale Not Illuminated
A recent shipment of SB-230 amplifiers, series #05802, has been noted to
have a defective meter [PN 407-185]. The meter scale information was put
on metal rather than clear plastic. As a result, the pilot light will
not shine through to illuminate the meter schale. The meter operates
properly, however.
Replace the defective meter at no charge to the customer.
------------------------------------------------------------------------------------------------------------------
Ok gang - that's it for the SB-2XX series.
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