Tutorials and Tech Support

This area will be reserved for tutorials and videos for the beginner tech or hobbyist who would like to try to perform some testing or adjustments on their own gear. If you have technical questions they can be emailed to mike@hudsonvalleyhifi.com and your question may appear in this area of the site with a response. Feel free to leave comments or questions on any page at the bottom.

Transistor Substitution
Turntable Setup Basics
Testing for DC Offset

***As always be warned that if you are attempting to work on any of your own gear be very aware that there is voltages present even when the unit is unplugged that can be harmful or fatal if contacted. Please learn how to be safe before attempting any of your own repair or testing.***


  1. While playing my Pioneer SX-1980 very loud one night – the bass would go in and out intermittenly. Was I pushing it too hard?
    Do you think I need to deoxit the controls; or are the power caps going out?

    • Hi Joe,

      Spraying the bass control pot with deoxit would be a good place to start. Give the pot a good second or two spray while working the control back and forth. After 10-15 seconds give it another quick shot. Allow the control to dry before powering back up. I usually stuff a paper towel around the control area to not make a mess as some will drain out.

      If this does not fix the issue you may have an issue with the EQ area of the receiver, such as a bad capacitor or leaky transistor. I cannot imagine stressing this receiver since it is so powerful unless you have a dramatic loss of power from an underlying problem. Start with the deoxit and if it does not resolve give me a shout.



    • Thanks a bunch for your help.
      This unit produces such low distortion that playing it loud (200 watts on the meters) does not hurt your ears. If I tried this on my Denon AV – I would develop a headache.
      I’ve re-capped the entire unit including the blue tangs on the tuner board. But I will take your wisdom and deoxit and faderlube the switches. Thanks!

  2. hi. great classic audio website! you do some great work.
    i have an old pioneer sx 636 receiver that was given to me by my father years ago and it has been on the blink recently. when turned on, it makes very loud static type sounds intermittently even with the volume down. i have experience fixing tube guitar amps, but none with this kind of stuff. any suggestions of what this may be, before i get the meter out and start testing voltages, etc?

    • Hi Daryl, thank you for your kind words.

      If your familiar with a meter the power supply, offset, and bias would be good things to check. In addition, get a can of Caig Deoxit and/or Faderlube to clean the control potentiometers. If you need the service manual for the test points and values of the above shoot me an email and I’d be happy to send it to you. The 636 is an awesome vintage Pioneer and well worth the effort to fix up.



  3. Have a Marantz 2270 that belongs to my brother, have done all you indicated. The unit has plenty power but sound is not clean, is like the speaker cones were loose. You notice it more on fm, phono is better. Both channels are the same. Any suggestions.

    • Hi Al, first thing would be to compare the pins on the power supply to the voltages in the schematic. Next, pull the pre out – main in jumpers on the back and figure out if the problem is in the amp or the preamp. Only test in aux at first since that shortens the signal path.

      You may have a failing signal transistor which is leaking and making noise. Also, have you cleaned up the controls with Caig Deoxot D5? Dirty controls can manifest in many different ways.

  4. Hi, nice site. I enjoyed reading the tech advice. My mom recently gave her Technics sa 600 receiver. I cleaned it inside and out including all controls and switches. It starts up fine, sounds good, all controls appear to function cleanly. The only thing I can’t figure out is why the fm section with a wire antenna hooked up will not get a strong enough signal to register past one notch thereby not able to switch to stereo. It appears as if hooking up an antenna makes no difference in the gain because when I detach the antenna lead there’s no difference in the signal. I seem to recall on another vintage receiver, Harmon Kardon, an internal way to fine tun for fm stereo. I remember tweaking it with a plastic screwdriver from below the receiver whenever it lost the stereo separation. It had a small opening just for that purpose. Can you provide any guidance? Thank you.

    • Hi Rick,

      If the FM tuner is not pulling in stations well it does not sound like a stereo separation issue; more likely, it sounds like the FM’s front end needs adjustment. Without the proper testing equipment this will be near impossible to do. One of our techs is very talented in tuner alignment and would be happy to repair the tuner for you. You can shoot me an email mike@hudsonvalleyhifi.com or 845-219-1730 for more info.


      • Thank you Mike. Makes sense. It’s as if the tuner section for fm can’t detect the antenna. However, when switching to am with a wire antenna attached in back the signal strength meter jumps up all the way for local am stations.

  5. Marantz 2270: Hi, I’m restoring this unit as its Regulated Power Supply P800 had several items that had failed. My trimpot is actually a pair of resistors. Could you recommend a suitable replacement for R809? Also, I was reviewing photos of your restoration of this same unit and it appears that the orientation of the negative connection to capacitor C805 was changed to face the trimpot from its original location. Is there a reason for rotating this 180 degrees or did I misinterpret the photo?

    • Hi Dave. Someone did a little custom hack work on your p800 board. Replace the resistors with a new multi-turn Bourns trimmer of similar or great value then the original.

      As far as c805 the cap needs to be oriented as the original one was. Some of the Panasonic caps are difficult to see in pics since the gold writing looks like the negative indicator.

  6. Hi Dave,

    I picked up a Technics SA-5470 Stereo Receiver which has a missing speaker protection relay. The ref no. is RLY601 and the part number is SSY21. Would you happen to know where I could get a replacement or maybe an equivalent? I have no idea what the specs are on the relay.



    • Hi John, I am sure you can get a relay to replace the one you have although you may need to do some creative wiring. Need some specs and connection info or your really looking for a needle in a haystack. Shoot me an email mike@hudsonvalleyhifi.com if you find any specifics. -Mike

  7. Hello,
    Nice site. I have an SX-1280 that has a static issue when the Tone switch is turned ON. When OFF, no static. I have opened to DeoxIT the switches and pots. Right channel now has a slight pop when Tone switch is turn ON. Unit was “re-capped and serviced” when I purchased it. Any ideas? Thanks.


    • Hi Micaiah,

      The switch may need to be disassembled and cleaned well internally. Otherwise there may be a slight DC leakage that is occurring from a failing component in the EQ circuit. That would obviously be more difficult to diagnose. There should be an opening in the back of the switch which you can really get the deoxit down into the switch and exercise it. If that does not work it may be time for some detective work. Shoot me an email mike@hudsonvalleyhifi.com with an update.

  8. I Have a 2270 after playing for a few minets there is a loud what seems like a ground short through the speakers.what should i look at to fix this? THANK YOU IN ADVANCE FOR HELP! BILLY,ORLANDO,FL.

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