Heathkit Service Bulletin - SB-6XX (Complete/Revised)
Joseph W Lutz
joelutz at JUNO.COM
Sat Jun 13 17:44:07 EDT 1998
May 26, 1978
SB-614 Bulletin
No:
Station Monitor SB-614-01
Incorrect Installation Instructions For Q107/Q108
Check installation of MPSA20 transistors [PN 417-801] at Q107 and Q108.
See drawing at right for proper basing and installation.
((Drawing shows the transistors mounted with flat side aligned with pcb
flat side. The transistor is mounted 1/4" above the pcb.))
Insert [PN 591-2662] will correct the manual [PN 595-1686].
-------------------------------------------------------------------------------------------------------------------
July 31, 1980
SB-614 Bulletin
No:
Station Monitor SB-614-02
Non-Linear Sweep in 100 Hz Position Only
+ + + + Information not yet available + + + +
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April 15, 1981
SB-614 Bulletin
No:
Station Monitor SB-614-03
Vertical and Horizontal Transistors Failure
+ + + + Information not yet available + + + +
------------------------------------------------------------------------------------------------------------------
That's all I show listed for the SB-614 (1966-89). Enjoy!
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January 21, 1980
SB-620 Bulletin
No:
Panadapter SB-620-1
Power Transformer Causes Shipping Damage
+ + + + Information not yet available + + + +
------------------------------------------------------------------------------------------------------------------
February 11, 1983
SB-620 Bulletin
No:
Panadapter SB-620-2
No Horizontal Sweep
+ + + + Information not yet available + + + +
--------------------------------------------------------------------------------------------------------------------
That's all I have listed for the SB-620 (1966-89). Hope to have the info
soon.
--------------------------------------------------------------------------------------------------------------------
March 13, 1967
SB-630 Bulletin
No:
Station Console SB-630-1
Operation of Buzzer Erratic
Replace relay [PN 69-38] with [PN 69-42] to improve reliability.
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That's all I have on the SB-630 [1966-89]. Enjoy!
--------------------------------------------------------------------------------------------------------------------
January 29, 1975
SB-634 Bulletin
No:
Station Console SB-634-1
Mismatch When Using 600 Ohm Input
Change the phone patch control to a 200K/1500/10 Ohm control, [PN 13-16].
Parts available in June 1975.
--------------------------------------------------------------------------------------------------------------------
February 10, 1975
SB-634 Bulletin
No:
Station Console SB-634-2
Phone Patch Control Miswired
In the first run of SB-634's, the phone patch control is wired with the
front and middle sections interchanged. This can be corrected by
interchanging the wires going to lugs 2 and 5, and interchanging the
wires going to lugs 3 and 6 of the control.
A mailing is being made to all SB-634 owners that will provide them with
rewiring information.
-------------------------------------------------------------------------------------------------------------------
June 6, 1975
SB-634 Bulletin
No:
Station Console SB-634-3
Schematic Error
The connection points K, L, M, N, P and R on the SB-634 schematic are
reversed from their proper order. For example, point K should be R, etc.
-------------------------------------------------------------------------------------------------------------------
October 28, 1975
SB-634 Bulletin
No:
Station Console SB-634-4
Use of Wider Toleranced Clock Chips
The [PN 443-601] clock chips have been selected for minimum flicker.
The [PN 443-601] is a hand selected version of the [PN 443-687].
With the following changes, hand selection is no longer necessary:
Change C201 from 30 pF to 51 pF [PN 20-190].
Change R237 from 15K to 18K Ohm [PN 1-162].
Change [PN 443-601] to [PN 443-687].
(NOTE: Either clock chip can be used witht he new value resistor and
capacitor.)
------------------------------------------------------------------------------------------------------------------
February 2, 1977
SB-634 Bulletin
No:
Station Console SB-634-5
Large Display Tube Part Number Change
+ + + + Information not yet available + + + +
-------------------------------------------------------------------------------------------------------------------
March 14, 1978
SB-634 Bulletin
No:
Station Console SB-634-6
Display Counts Twice Each Second
Check the brand of [PN 443-7] IC's used at IC204. If it is a TI brand,
replace it with a Fairchild brand.
The TI brand of IC was found to be causing a small glitch on the
positive-going input of IC204 as the signal reached 1 volt, causing one
count from the glitch. Replacing with a Fairchild brand IC corrected the
problem.
All Replacement Parts stock of [PN 443-7] IC's are now Fairchild brand.
--------------------------------------------------------------------------------------------------------------------
+ + + + SB-634-7/8/9 are not yet available + + + + [Sorry]
--------------------------------------------------------------------------------------------------------------------
November 16, 1984
SB-634 Bulletin No:
Station Console SB-634-10
Dual Electrolytic Capacitor NLA
The 2 x 20 uF electrolytic [PN 25-270] at C211A/B is no longer available
from Heath Parts Replacement. Two 22 uF electrolytic capacitors [PN
25-955] are used as a replacement.
After the old capacitor is removed from the circuit board, use a sharp
pointed tool and enlarge the negative (-) hole so both negative leads of
the replacement capacitors will fit into the hold. Bend the leads of the
replacement capacitors so they fit flush with the board. [[The negative
leads form the bottom of the 'triangle' that is made when the two (+)
leads are placed in their respective holes]].
-------------------------------------------------------------------------------------------------------------------
August 31, 1989
SB-634 Bulletin
No:
Station Console SB-634-11
Minutes or Hours Digits Count Twice As Fast As Seconds
When the minutes or hours display sometimes advances just as if SW2
minutes Set switch [PN 60-6] or SW3 Hours set switch [PN 60-6] were
activated, a high resistance path may have developed across the Set
switch contacts. Replace the appropriate switch to correct the problem.
--------------------------------------------------------------------------------------------------------------------
That's all I have on the SB-634 [1966-89]. Enjoy!
--------------------------------------------------------------------------------------------------------------------
February 21, 1975
SB-644 Bulletin
No:
Remote VFO SB-644-1
Switches JAM
The first run of SB-644's include hardware that may limit the travel of
the cancel bar in the pushbutton switch assembly. You may receive
requests to replace a switch which appears faulty. Advise checking
mounting hardware and replace with four screws to [PN 250-172].
-----------------------------------------------------------------------------------------------------------------
May 20, 1975
SB-644 Bulletin
No:
Remote VFO SB-644-2
VFO FM-ING
The following changes are being made to revive uniformity between the
SB-644 and SB-104 VFO's:
On the 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]
D1202 from 1N191 to 1N485 [PN
56-24]
ZD1201 from 10V to 7.5V [PN
56-97]
Although the FM-ing problem may not exist when operating from a 13.8V DC
power supply, the FM-ing problem might occur if it is being operated from
a "field day" supply. Make these changes only when a complaint is
received.
-------------------------------------------------------------------------------------------------------------------
May 11, 1976
SB-644 Bulletin
No:
Remote VFO SB-644-3
Schematic Correction
The following correction is to be made to the schematic in the [PN
595-1656-03] Manual:
On the SWITCH circuit board the line from junction of C1251 and C1252
whuld connect to the cathode of D1262 instead of to coil L12.
------------------------------------------------------------------------------------------------------------------
February 2, 1978
SB-644, A Bulletin
No:
Remote VFO SB-644-4
VFO Dead
Check the solder pads at each corner of the [PN 85-1205-3] circuit board
to confirm that all solder resist has been scraped away. If the solder
resist is not removed at these points, the oscillator will not run since
the board is not grounded.
-------------------------------------------------------------------------------------------------------------------
May 30, 1978
SB-644, A Bulletin
No:
Remote VFO SB-644-5
Oscillations Caused by Overdriven Switching Transistors
Switching transistors Q1255, Q1256 and Q1257 may sometimes oscillate due
to their emitters being at zero potential, grounded by L1255.
To prevent this, replace L1255 with a 470 ohm resistor [PN 6-471]. The
resistor will have to be installed on end (vertically) due to narrow hole
spacing of L1255.
Typical emitter voltage will now be about 1 volt.
This will be covered by insert [PN 591-2657] in the latest production
run.
Circuit board [PN 85-2037-3] will incorporate this change.
--------------------------------------------------------------------------------------------------------------------
August 15, 1979
SB-644A Bulletin
No:
Remote VFO SB-644-6
Schematic Correction: ADD R1227
The schematic in the SB-644A Manual [PN 595-2055-02] doesn't show R1227
[3900 Ohm] from source of Q1203 to ground on the Buffer board. Add this
to your schematic.
------------------------------------------------------------------------------------------------------------------
August 15, 1979
SB-644A Bulletin
No:
Remote VFO SB-644-7
Excessive Second Harmonics on VFO Frequency
The following changes will lower the second harmonics of the VFO
frequency and reduce cross-coupling between Q1256 and Q1257. This will,
in turn, reduce the RF leakage on the VFO output jack when that line is
switched off.
Change:
R1268 from 470 Ohm to Toroid Coil
[PN 40-1882]
Q1256 from [PN 417-205] to [PN 417-134]
Q1257 from [PN 417-205] to [PN 417-134]
Install:
Shield [PN 206-1257] as follows:
- Drill two .070 holes in ground foils at indicated spots. ((one hole
shown at what looks like between L1253 and C1287[??]-the component that
is between L1253 & L1254. The other hole is at the end of R12, right
down from 'K' & 'J'))
- Mount shield so that it does not touch transistors, coils or other
leads.
-------------------------------------------------------------------------------------------------------------------
That's all I have on the SB-644, A [1966-89]. Hope it helps.
73 de Joe W7LPF/4 [NNN0KUU]
QWCA - SOWP - NCVA - FISTS - RCC
Gordonsville, Va 22942 [Orange Co]
Wanted: SB-644[A]
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