[Motorola] M4548

[Glen Zook]

The actual replacement part number would be 48R134548.  The 48K number is the part number when used in production and the 48R number was used for replacement parts.

I am trying to remember and if I remember correctly the M4548 transistor was used in the HHT series of Motracs maybe even an "A" or "B" model.  Now I don't remember if it was used in the audio stages or in the high power oscillator that was used to run the transformer for the B+ and B++.

It has been almost 30 years since I have even seen a "B", "C", "D", or "E" model HHT Motrac and going on 40 years since I have seen an "A" model HHT Motrac.  The "A" model came out in 1957 and during the time I owned the Motorola reconditioned equipment center for the south-central United States (1970 until Motorola basically went out of that "end" of the business in 1979) we did not recondition any "A" models.  The "B" through "E" models were reconditioned at various times all the way through 1979.  Of course the LHT and MHT series were reconditioned all the time.

Generally any of the germanium TO-3 power transistors will work especially if you substitute one of those used in the high voltage oscillator section in an audio circuit.

I still have some of the older Motorola semiconductors left over from when I acquired the parts stock of a large self maintained two-way radio system that went to a General Electric 896 MHz trunk system in the late 1990s.  So far I haven't found any of the transistors but I still have a place or two to look.

Glen, K9STH

Website:  http://k9sth.com


--- On Tue, 6/17/08, Eric Lemmon <wb6fly at verizon.net> wrote:

You've got a good memory!  However, the transistor in the Motrac push-pull audio amplifier stage is an M4584, not an M4548.  I went through the entire Motrac manual, and found that the great majority of transistors were M9xxx series, and the M45xx series were usually in audio or low-frequency stages. I could not find an M4548 in the Motrac or Mocom-70 manuals- the latter being of similar vintage.
 
For what it's worth, the Motorola part number of the M4548 is 48K134548, but it is no longer available from Motorola Parts.