Fisher model 173 stereo receiver weak sound form right side

Discussion in 'Technical Repair' started by secrets, Oct 13, 2016.

  1. secrets

    Thread Starter New Member

    Oct 13, 2016
    1
    0
    Hello everyone I have a Fisher model 173 stereo receiver that I would like to work on . This receiver powers on and plays audio through both channels right and left .The headphone output works as well . I learned that the right side output plays but has a weaker less powerful sound as to the left .I tried the record rca outputs to see if the same thing appears when connected to an external amplifier from the rec out terminals and I found they sound as they should left and right are equal on rca outs .I then tested all of the inputs to see if there is and change but the audio sound on the right is still weaker no matter the input . That goes for am and fm as well .There is nothing burned inside . I did find a service manual online but I am not skilled to that level but I can understand basics . I do have a multimeter and soldering tools along with a audio probe I made from online instructions .I probed around a bit from the input section and found what appears to be the pre drivers which are small transistors as well as some carbon film resistors close to those transistors that i suspect might be in question . With the audio probe I can hear hissing coming from those carbon resistors and I read they crystallize over the years and produce noise . With speakers connected you cannot hear that noise unless I use the amplified probe so I don't think that would be my problem . I planned to change the input pre amp stage transistors but would like to ask for some advice or instructions on where and how to test different areas . Here is the link for the service manual It states for the 10 but the same for 173 .
    http://www.vintageshifi.com/repertoire-pdf/Fisher.php
     
  2. BR-549

    Well-Known Member

    Sep 22, 2013
    2,004
    394
    If you know the basics, it shouldn't be much of a problem. You have two identical audio channels. One channel you believe to be good and one that appears weak. A scope would be nice.....just input the same signal in both channels......follow thru and compare channels.

    What kind of meter do you have and can you borrow a scope?

    Are you sure the resistors are hissing?
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,142
    3,054
    I wouldn't change out any transistors until you have a better diagnosis, unless this is very easy for you. Since the headphone and line-out ports are working, it seems the pre-amp is probably fine and the problem is more likely in the power amp.

    Have you tried toggling the speaker selector switch? Your problem could be as simple as a bad connection in that switch.

    Those test points near the big output coupling caps C47 and C48 (which could be a problem) are worth looking at.
     
    Last edited: Oct 15, 2016
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