Replacement Tranistors for Ten-Tec 544

Discussion in 'Radio Circuits, Repair & Performance' started by KF5JKA, Dec 31, 2013.

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  1. KF5JKA

    KF5JKA Ham Member QRZ Page

    Ok..So I bought an old 544 few weeks back and I love this thing! However I subsequently blew up the pre-amp transistors in it (TRW PT3647's, one of the pair opened up completely) and they don't make them anymore..Sooo looking for something that might work the 2N3553 looks like the closest match I can find. The PT3647's that blew in my pre-amp circuit are actually used as the finals in some of Ten-Tec's QRP rigs like the 505 so anybody out there know if there is anything better than the 2N3553? Thanks

  2. VK5TM

    VK5TM Ham Member QRZ Page

    Contact Ten-Tec, apparently they still have parts available.

    Alternately, after looking at the manual, 2N5109's maybe?

    Terry VK5TM
    Last edited: Jan 1, 2014
  3. KF5JKA

    KF5JKA Ham Member QRZ Page

    The 5109 looks good except it is rated for only one watt..I need at least 5 watts to drive my finals..Thanks for the info!
  4. W9GB

    W9GB Ham Member QRZ Page

    The 2N3553 is a TO-39 case transistor
    The 2N3553 is a good device, except it is designed for 28 VDC service and lacks efficiency at 12 VDC.

    Earl Andrews covers its usage in the Ten Tec Argonauts (and replacements)

    Earl recommends the MRF 8004, discussed in article above.
    Dan's Small Parts carries this TO-39 case transistor.

    NTE Electronics NTE235 (TO-220 case) may be a possible substitute.

    The Motorola MRF 476 was very popular in this power class for CB radios in the 1970s and early 1980s.
    4 watts RF output was typical.

    HG Semiconductor

    HG datasheet for MRF476 RF transistor (TO-220AB case)

    HG Semiconductor Co., Ltd.
    West 2nd Floor, 2# Building, 88 Qianyao Road,
    Wuxi, Jiangsu, China
    Telephone: +86-510-81023902

    Attached Files:

    Last edited: Jan 2, 2014
  5. KF5JKA

    KF5JKA Ham Member QRZ Page

    Thanks for the information! I did find some 2n3553's and they seem to work fine along with the new finals I installed at the same time..I can get full rated output from the unit..I will look at MRF 476..
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