Don't Miss

A, AF, AX, D, DF, DX Version of HOT

By on December 9, 2009


If you repair CRT Monitor I’m sure you might have came across Philips Horizontal output transistor  (HOT) that have many version behind each part number. For example, BU2508A, BU2520AF, BU 4522AX, BU4523DX and etc. For your information the A version does not have a built in damper diode but the D version have damper diode in it. You may refer to semiconductor databook or from the internet to see the specification of each HOT.

The question is, could an A version be replaced by the D version and vice versa? I understood that many repair technicians replaced the A version with the D version and did not replace the D version with the A version. The reason was that the HOT with a built in damper diode is much better than the HOT without damper diode in it. Yes, it is true that many of the Monitor in the market with the A version can be replaced with the D version but i did came across certain brand of Monitor that only can run well with the original part number! That means, the D version would not last. It worked for only a week or two before the HOT blow again. Putting back the A version solved the problem.

Since HOT is easily available from the market, i suggest that you put back the exact part number to avoid call back because a repeated repair is a loss to you and your business.



  1. Henrique

    December 18, 2009 at 8:39 am

    Hi Jestine, i amm brazilian tecnic, my english is pooor, but a explanation is diode damper intern warm more. Basicamente em portugues é que o diodo damper quando interno ao Hot ( TSH) aquece alem do que foi previsto na maioria dos projetos, ou seja um dissipador projetado para dissipar o aquecimento apenas do transistor, não conseguira dissipar o aquecimento do transitor e diodo juntos, portanto deve se evitar usar transistores com damper no lugar de sem damper. Por ser uma falha ligada ao calor raramente o problema acontece imediantamente, costuma levar de dias a semanas.

  2. admin

    December 22, 2009 at 11:26 am

    HI Henrique,

    Thanks for your contribution. I got to use google translation to translate it.


  3. Amir Mukhtar

    September 7, 2011 at 3:06 pm

    Sir Jestine,
    Your answer is complete and appropriate in this regards. But one problem always came across of several repairer life in repairing. for example, vendor deliver or sale non-genuine transistor / fake quality transistor which not works upto the mark and blow up again. so therefore, what is criteria to check the original component.
    also point to be noted, that fake transistor showed up perfect by Avo METER checking.
    kindly guide us in order to get original component from market shop.

    thanks you
    Amir Mukhtar

  4. admin

    September 9, 2011 at 2:52 am

    HI Amir,

    Is hard to differentiate it sometimes. One has to test it and see the performance.


  5. J. Lukmono

    March 1, 2012 at 4:55 am

    hello, pak. saya Joko dari surabaya.
    saya punya monitor hp5502 14 inci, horizontal size terlalu melebar.
    saya cek bagian h. size tak ada transistor. yang ada FET IRF630M di sisi heatsink flyback. FET sudah saya ganti baru sekarang malah transistor C5929 short. Lalu saya coba ganti dengan transistor C5386
    , tapi selalu short.
    Tolong pencerahannya.....trims

    • Jestine Yong

      March 2, 2012 at 10:58 am

      Hi Joko,
      Kamu kena guna ganti komponen yg tulen. saya cadangkan anda masuk laman web di bawah krn flyback boleh menyebabkan masalah tersebut:



Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.