Sansui 9090db protection flashing red.

Discussion in 'Exclusively Sansui' started by arfz28, Aug 23, 2004.

  1. arfz28

    arfz28 Member

    Hi I have a friends sansui 9090db at my house that needs some work on it I hope it might be an easy fix. The auto protection just keeps flashing red and wont turn green. I checked all the fuses that I could find including a couple underneith the bottom cover of the unit all the fuses are good. I cleaned all the pots with deoxit while I had the unit apart still no luck. ANY ideas that will fix this problem? If I cant fix it I am sure it will most likly go back on his basement self were its been sitting for a few years what a shame. All the lights lit up on the faceplate which can be a problem on a sansui 9090db, unit itself is about a 7 out of 10. Thanks all.
  2. LBPete

    LBPete Rolling Along Subscriber

    Check the resistance values of the “fuse” resistors on the driver board. They are a common reason 9090DBs go into protection. These resistors tend to fatigue over time and go out of range or even open. They are a kind of powder blue color. If they look burned or swollen they are suspect but they don’t necessarily need to be discolored to be bad.

    Both channels are represented on the driver board in a more or less mirror image from side to side. The quick check is to just compare the resistance value of a resistor on one channel to its twin in the other channel. This isn’t fool proof because both could be bad but it is quick.

    - Pete
  3. arfz28

    arfz28 Member

    LBpete, which board is the driver board? Is it the one right smack in the middle of the receiver toward the back that stands tall and has a bracket that helps hold it in place? Which 2 resistors need to be replaced there is quite a few of them on this driver board?

    I read some other threads on this sansui protection problem. One guy said to try this.

    Those resistors R33 and R34 don't have to be fully open to cause this problem. Replace them if they read anything over 200 ohms. When they get out of tolerance they cause DC voltage on the outputs and the protection will not release if this is the case. A quick test if you are lucky and your protection board has fuses (some have jumpers) is to remove the fuses and see if the unit will go out of protetion if so it is problably DC on the outputs that is causing the problem. If your's has jumper measure for any DC voltage on the jumpers if there is that is what is causing the protection. The protection board is under the bottom cover. It has a relay on it hard to miss.

    So I am thinking this guy is talking about the same resistors as you are that could be giving me the problem. Most likly numberd R33 and R34. So I went ahead and pulled the 2 fuses in the protection board that is under the bottom of the unit and then I turned on the unit. Protection light flashed red for a second or two and then turned green like it should. So maybe if I knew where these 2 resistors are located and if I could get ahold of some replacements I can probably solder them in and maybe fix this unit. I looked all over but I still cant find a R33 OR R34 resistor. WHERE are this little devils. Thanks for the help LBpete.
  4. LBPete

    LBPete Rolling Along Subscriber

    The driver board is the one that stands vertically from the power supply board. It has a black bracket that holds it in place. The resistors and other components are numbered on the board. Just look carefully. The “fuse” resistors are a light blue/gray color. Check all of them with an ohmmeter. These are all common resistors. Radio shack or any electronics supply house will have them.

    I think that is CDFixer’s post you dug up. If memory serves R33 and R34 are both either 150 ohm or 180 ohm resistors depending on whether you have the early or late design driver board. It doesn’t sound like you have a schematic so just match the color code of the resistors.

    Please be careful. To paraphrase EchoWars, the bigest reason for expensive repairs is well meaning friends!

    - Pete
  5. arfz28

    arfz28 Member

    Thanks LBpete I will look tomorrow in better light maybe take that driver board out if I can and see if I can find those 2 resistors. My friend actually has the scamatic for the unit but I didnt take it with me because I cant read the things anyway. I will ask him if I can try to fix it or he can set it back on the basement shelf and go to waist. He doesnt wont to stick much money in it. But he wont sell the unit either I think it was his older brothers at one time. I cleaned the unit up and hopfully after he seas how nice it looks he will want to get it fixed and use it.
  6. Patrick620

    Patrick620 Audio Enthusiast

    Awesome info, guys. Fixed it right up. Shes ready to rock now. Thanks. Sorry no pics but I let the kids borrow my camera for their trip to KC.
  7. LBPete

    LBPete Rolling Along Subscriber

    Wow, you are digging deep to find this old tread. Glad it helped.

    - Pete
  8. CDFixer

    CDFixer Number 1 USC Trojan Fan Subscriber

    LB maybe we need a sticky on X0X0 and X0X0DB Protection problems
  9. naderpe

    naderpe AK Subscriber Subscriber

    Those old threads are invaluable. Kudos to LBPete
  10. LBPete

    LBPete Rolling Along Subscriber

    Kudos to CDFixer. He was the first to figure it out.

    - Pete

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