Heathkit Service Bulletins - HD-1418 (Revised & Complete)

[Joseph W Lutz]

                        May 18, 1984
HD-1418                                         Bulletin No:
Active Audio Filter                                     HD-1418-1

                              Parts List Correction - S1 and S2

In manual [PN 595-2980], page 8, and HD-1418 Blue Book, page 96, correct
the parts list as follows:

        S1 pushbutton switch from [PN 64-919] to [PN 64-920].
        S2/3/4/5 four-section pushbutton switch from [PN 64-920] to [PN
64-919]
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                        February 24, 1989
HD-1418                                         Bulletin No:
Active Audio Filter                                     HD-1418-2

                Unit Doesn't Operate After Assembly

[[[[[[[[[[[[[[[[See Bulletin No:  HD-1418-3]]]]]]]]]]]]]]]]]]]]]]]]
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                        August 31, 1989
HD-1418                                         Bulletin No:
Active Audio Filter                                     HD-1418-3

                     Unit Oscillates With PN 443-733 IC Installed

In earlier production of the HD-1418 Audio Filter, the Signetic brand of
MC1458 IC at U2-U12 and U15-U17 would cause the unit to oscillate.  To
correct this problem, these ICs were then changed to LM358 ICs [PN
442-733].  Factory Service found that the PN 442-733 ICs also caused the
Filter to oscillate.  To correct the oscillation problem, the following
change is made:

Change:  U2-12 and U15-U17 from LM358 IC [PN 442-733]
                                             to a TI brand MC1458 IC [PN
442-839].

QA found the oscillation occurs in U7 and U11 when an IC other than a TI
brand ICs are installed.  Either a TI brand of PN 442-21 or a PN 442-839
can be used as a replacement part.

This bulletin supercedes HD-1418-2.
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Thats everything I hold up to 1989 that covers the HD-1418.  Enjoy!
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73 de Joe  W7LPF/4  [NNN0KUU]
QWCA - SOWP - NCVA - FISTS - RCC
Gordonsville, Va 22942 [Orange Co]

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