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Repair newb - need help fixing sub amplifier

Discussion in 'Troubleshooting and Repair' started by dgsaudio, Oct 27, 2014.

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  1. dgsaudio

    dgsaudio

    1
    0
    Oct 27, 2014
    Hello all - I was given an Infinity Entra Sub by my neighbor. The sub is getting a little sound from the amp, but mostly distortion. I opened the amp up to find signs of overheating near some transistors/diodes in the power supply. I'm wondering if this is the cause of the amp not working? It should be easy enough to replace the parts to find out. The transistors I've identified easy enough - NEC D882 and B772 pairing, but I'm not familiar with diodes. The board says "ZD..." is this a zener diode? And the diodes say "15" on them - is this 15v, 1w? How can I tell what wattage I need? Any help on those questions and anything else that I might need to know before I order parts would be appreciated!

    Also, to avoid having to purchase 10 transistors/diodes each off of ebay, if anyone wants to send me a few, I'll compensate you appropriately via paypal, I'd appreciate it. Thanks!

    20141026_185538.jpg 20141026_184840.jpg
     
  2. davenn

    davenn Moderator

    13,946
    1,986
    Sep 5, 2009
    hi there
    welcome to Electronics Point :)

    yes ZD is a zener diode :) the 15 may well refer to the voltage rating ... wattage rating .. hard to tell ?

    only a service manual (parts listing) would confirm the zener's ratings

    Dave
     
  3. MstrMiyagi

    MstrMiyagi

    2
    1
    Jan 7, 2018
    I just got a old entra sub with the exact same symptoms, so I'm reviving an old topic:
    Dgsaudio, did you ever fix your entra sub ?

    If not, I found the service manual and the zener diodes labeled ZD301 and ZD302 are the same and listed as "DIODE 15V 1/2W HZ15-3" in the manual.
     
    davenn likes this.
  4. davenn

    davenn Moderator

    13,946
    1,986
    Sep 5, 2009

    thanks for the confirmation :) ....
    I really believed they were 15V as they were marked :)
     
  5. Wayne Phillips

    Wayne Phillips

    61
    1
    Jan 7, 2018
    Fixing any amplifier comes with a set of problems..not only can it be costly if you are just popping heaps of parts and watching them go pop!

    I'am a service tech for a living and I can say read plenty before jumping into it!

    You must be able to use ohms law plus use test gear ie scope/meters..etc.

    What is the cost of this unit and would it be quicker just to replace.


    Now getting into the circuit if parts have over heated there many be something that has shorted out..oh a shorted speaker will damage a amplifier.
     
  6. MstrMiyagi

    MstrMiyagi

    2
    1
    Jan 7, 2018
    Wayne,
    Thanks for your words of wisdom, my electronics knowledge is beginner to novice, so I will definitely need to do some more research.

    I already removed a PNP and NPN transistor from the main amplifier board, both of which tested good using a resistance check and diode test function of my multimeter.

    Also checked the speaker, works fine when using a known good amplifier.

    I just found a overheated zener diode on the main amp board, labeled D807. Its overheated to the point where all the markings on the diode are gone. The service manual list it as "ZENER DIODE 30V HZ-30-2 05000881", but nothing comes up when I try to google the part#. Does anyone know if I can just replace it with any 30V zener diode ?

    Entra_D807.jpg
     
  7. Wayne Phillips

    Wayne Phillips

    61
    1
    Jan 7, 2018

    The 2w 1k resistor next to the zener looks like it's tide to it. Have you checked the voltage at this point also the amplifier does not need any speaker load connected to it as it's being worked on.

    One tip is the use a 100w or 60w bulb limiter in the primary 240 ac side as this will act as indaction lighting up bright if there is a short.

    With a working amp the lamp brightens up at power up then dims out but, as the amplifier draws current under load the lamp will brighten up.
     
  8. kds9591

    kds9591

    7
    1
    Jan 18, 2018
    Hi

    Zener diodes are always marked with the voltage on them not the wattage.

    If this is a car amp (you don't say if it is or not) a good place to get advice on your Infinity amp repair is the car amp section on the link below. There is one poster named Perry Babin who not only repaired car amps of all brands and models he even sells a car amp repair course. If you post your problem there it is almost certain he will reply. He really is informative and will actually walk you through troubleshooting it. If it's not a car amp they also have another forum for home audio. Hope this helps.

    http://www.diyaudio.com/forums/car-audio/
     
    Last edited: Jan 20, 2018
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