Technics SA-290 Relay trouble

Discussion in 'AV Receivers & Amplifiers' started by Zundarium, Aug 4, 2013.

  1. Zundarium

    Zundarium
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    Hey Forum Members! This is my first Post and i hope for an Answer.
    See, I recently began collecting and repairing older stereo systems. Everything from tubes to never units, but mostly old ones. I'm here with a Technics SA-290 And i fixed these problems here using this guide my friend provided me with, and followed himself. http://gmorehou.wordpress.com/2013/05/12/technics-sa-290-common-problems/
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    Also Under the power meter, on its circuit there is (one i believe) of the resistors Getting REALLY hot, hot enough to feel it when hovering your hand over the area (with open Casing) Is that normal?
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    And the Power transformer gets Very hot, the longer it runs.
    I Hope somebody knows Solution(s) for the problems~

    -Zundie
     
    Last edited: Aug 5, 2013
  2. davismv

    davismv
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    I have an SA-290 and 4 power meter lights did not work (the first 2 for each channel). Seems like this happens to many of these receivers based on pictures all over the Internet and on eBay – I discovered that ONLY two LED's actually need to be replaced - the 1st LED on the left and 1st LED for the right channel. The second LED's will start to function normally after the repair. I suspect that the first two LED’s actually burn out as they are always on and perhaps the voltage is a little high for them (an engineering fault by Technics?).

    Here is the fix, which is straightforward but tricky if you know how to solder and are handy. I would only attempt if you are confident and detailed. This worked for me.

    Open the receiver up, remove both the meter and signal strength circuit boards. There are plastic clips that simply hold these boards in place. Both come out (connected by a 2 wire ribbon cable) - be careful not to damage the cabling. Push down on the white ribbon connector on the main board and pull up on the larger ribbon cable to remove the wiring altogether and you now can work on the meter lights separately from the unit. Set stereo aside and carefully remove the rectangular plastic film off of the meter panel to expose the LED’s (the LED’s are behind a thin plastic translucent film and are all encased in a single white plastic enclosure). I carefully used a razor blade and started from one side and the entire rectangular piece of film came out with no tears or rips. Set aside carefully when removed (keep the sticky side clean). Get a drill and drill out the 1st LED to the left and to the right of the middle. These are the first LED’s that light when the volume is lit up. You will need to carefully drill them as they are attached to the white enclosure and you don’t want to damage the circuit board. Once drilled out, unsolder the leads from the back and then remove all old leads and pieces of the old LED.

    Purchase (2) green LED lights that are 5v (make sure they are minimum 5v - but not 12v - as I measured and the voltage being applied is 5.3v). You can get these from Radio Shack, Fry’s Electronics, or online.

    Here is the tricky part: Situate the 2 new LED’s in the drilled out sockets to see if they fit (LED needs to be below the surface of where the film cover is placed). I had to re-drill the holes in the white plastic slightly larger to make the LED’s fit so it took a few attempts. Once they fit, then remove the LED’s – don’t solder them yet. Reattach the ribbon cable and insulate the boards from anything metal in the receiver – like a towel. Power the unit on, apply audio (perhaps a radio station), and turn up the volume partially. Hold your new LED CAREFULLY to the solder points on the back where you removed the old ones to determine polarity. If the new LED does not light up, then reverse the leads. Once you get the polarity correct, your new LED will light up as you hold it against the solder holes. You will also notice that the second burned out LED will now light correctly as well. Make a note of the polarity and positioning and repeat for the other channel. Turn receiver off, and solder the LED’s in the sockets and ensure that the LED is behind where the rectangular film is placed.

    Reapply the rectangular film (stickiness should still be good enough to hold fine if it stayed clean). Replace the power meter and LED boards back into the unit and then enjoy your functional power meter!

    I am an electronics hobbyist and determined this by measuring voltages, resistances, and other parts after comparing to the schematic. That is how I determined that only two of the 4 LED’s needed to be replaced.
     
  3. Arcam_boy

    Arcam_boy
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    The threads over 3 years old but thanks for the post! :thumbsup:
     

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