6146 Type Tubes

[Charles Seitz]

I came upon the following service notes for bthe HW-101:

========================================================

JANUARY 20, 1978

HW-101 BULLETIN NO:  SSB TRANSCEIVER HW-101-18

RF CHOKE IN FINAL PLATE CIRCUIT OVERHEATS OR

DIFFICULT TO NEUTRALIZE ON 10 AND 15 METER BANDS


6146B tubes in the final amplifier may be causing this problem. To correct,
replace with 6146A tubes.

A label will be installed on the back panel of the HW-101 recommending the
use of 6146A tubes only. The 6146B tubes should not be used as a
replacement.

=========================================================

NOVEMBER 20, 1978

HW-101 BULLETIN NO:  SSB TRANSCEIVER HW-101-39

IDENTIFICTION OF THE 6146A TUBES

The 6146A tubes [PN 411-75] used at V8 and V9 of this unit are marked
'6146A' in white ink on the side of the tube. These tubes may also have
'6146B' etched in the galss. These tubes have been reworked by G.E. and are
acceptable for use in the HW-101. Most tube cartons will contain the
following insert to explain the situation to the customer:

IMPORTANT INFORMATION;

THE TUBE SUPPLIED WITH THIS NOTICE IS TYPE 6146A, AS PRINTED ON ONE SIDE OF
THE TUBE, EVEN THOUGH THERE MAY BE A 6146B ETCHED ELSEWHERE ON THE TUBE
ENVELOPE.

ALWAYS REPLACE V8 AND V9 WITH 6146A TYPE TUBES

Replace the backing from this label and place the label at any convenient
location inside the cabinet top.

 ===========================================================================


May 15, 1979

HW-101 BULLETIN NO:  SSB TRANSCEIVER HW-101-49

CHANGEOVER TO 6146B FINALS

The 6146A final amplifier tubes are no longer available from the
manufacturer. Future productions runs will use the 6146Bs. These are GE
brand tubes and have been tested in the HW-101. No difficulty was
encountered in neutralizing the finals; nor did the RF choke in the final
plate circuit overheat. The tube replacement label [PN 390-146] should be
removed from all units brought in for service.

 ===========================================================================

I'm not sure if these apply to the other HW and SB ham equipments.  Someone
might compare the final amplifier circuity and mechanical layout of other
units to make an educated guess about acceptable practices.

There's too much ambiguity here.  Follow Glen Zook's advice for the least
trouble prone approach to replacing your finals.



                                                          ---  CHAS  WA2DYA

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