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Heathkit AR-15

Discussion in 'Troubleshooting and Repair' started by mdillah, Dec 15, 2020.

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  1. mdillah

    mdillah

    1
    0
    Dec 12, 2020
    Hi Guys:
    I am new to this site and would greatly apricate some help on solving lack of audio from both channels regardless of source. I have provided a schematic.
    these are my findings on the flowing voltages from Q201 & Q202, the voltages from Q203-Q207 are ok
    Q201- b-.6v, correct, e-0v correct, c-0v should be 8.5v
    Q202- b-0v, should be 8.5v, e-0v should be 7.9v, c- 27.7v should be 14.5v
    Thanks
    Mustapha
     

    Attached Files:

  2. bertus

    bertus Moderator

    1,759
    677
    Nov 8, 2019
    Hello,

    Here is the extracted amplifier part of the posted schematic:
    Heathkit-AR-15-amplifier.png It looks like a C-E short of Q201, as both are at 0 Volts.
    Could you take out Q201 and measure the transistor?

    Bertus
     
  3. Ylli

    Ylli

    354
    99
    Jun 19, 2018
    Are these incorrect voltages on both channels? Normally a failure of both channels is from something that is common to both channels, like a power supply voltage. A bad Q201 in one channel will not affect the other.
     
    bertus likes this.
  4. bertus

    bertus Moderator

    1,759
    677
    Nov 8, 2019
    @Ylli , The power seems to be there. Even the 27 Volts.

    Heathkit-AR-15-power.png
     
  5. Ylli

    Ylli

    354
    99
    Jun 19, 2018
    Yeah, I just used "Power Supply" as an example of something that was common to both channels.
     
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