Recent content by mubs13

  1. M

    Help needed - Sansui AU-9900 transistor substitution

    Hey all, Thought I should give a quick update on the progress and final success. I got some 4148 diodes and replaced D06 with a pair in series as suggested by Lee above. Adjusted bias and dc offset and connected it all up in my main system. Its been playing sweet tunes since then :) sounds...
  2. M

    Help needed - Sansui AU-9900 transistor substitution

    You sir are a legend! :bowdown: You have just made my day. Yes, looks like it was D06 indeed. I took D06 out and it measured open. Just to be sure, I swapped D06 with D05 (paired 4148 on working channel) and guess what the high DC output just moved to the other channel! So its certainly looking...
  3. M

    Help needed - Sansui AU-9900 transistor substitution

    Hi Lee, I had replaced Tr02 with KSA992 and I have checked again and it looks to be soldered well. C18 and C20 both are installed with correct polarity. I have not replaced D06 and as far as I can see it looks to be original (small black peppercorn shaped diode). I did notice that D05 on other...
  4. M

    Help needed - Sansui AU-9900 transistor substitution

    Thank you sir, I am in no hurry, so please feel free to respond when you can :)
  5. M

    Help needed - Sansui AU-9900 transistor substitution

    Hi all, Apologies for the late update on this. I had been sidetracked due to job and other family priorities. Progress is slow but I have not given up on my amp yet :) I was able to take some measurements before as well as after the protection kicks in. Here is what I found: Before protection...
  6. M

    Help needed - Sansui AU-9900 transistor substitution

    I guess it's time for me to get one :) I'll head to my local hardware store to get the parts and make one asap. Thanks for the tip. Would a 100watt bulb do?
  7. M

    Help needed - Sansui AU-9900 transistor substitution

    Hi John, I have double and triple checked the pins, it's installed correctly. Also, the same transistor Tr05 on the other channel is installed same and is working fine. I feel it's probably something else as you have suggested. I am also worried that if I leave the amp on for too long, it might...
  8. M

    Help needed - Sansui AU-9900 transistor substitution

    Did some more investigation as below. Tried to measure DC output on faulty channel before the relay, after the protection kicks in. Is the circled point in the diagram below correct to measure dc offset before relay? The 'brown' point had 38V DC measured with negative to the ground...
  9. M

    Help needed - Sansui AU-9900 transistor substitution

    Hey all, Thanks for all the help. In between my kids and the job, I was finally able to get some time to work on my au-9900 this weekend. I replaced all the transistors on the F-2583 driver board as per the replacements given. I replaced them all because I do not have a proper transistor...
  10. M

    Help needed - Sansui AU-9900 transistor substitution

    Great, one less thing to worry about :) I do plan to check and replace other components too as needed. I will also be recapping the driver board as well as the power supply boards. Finding the resistor and capacitor replacements are easy, its the transistor replacement I needed some help with...
  11. M

    Help needed - Sansui AU-9900 transistor substitution

    Hi all, I am in need of a bit of advice with transistor substitutions in AU-9900. Mine is in need of repair, having issues with unstable bias and slight distortion in one channel. I was thinking of replacing the usual suspect transistors on the driver board (F-2583) as it still has original...
  12. M

    Pioneer SA-7500 - zero bias on one channel - need help

    Based on forum search result, MJ15030 MJ15031 have been suggested as good substitutes for 2SD357 and 2SB527 drivers. Is that a good substitute to go with for SA-7500?
  13. M

    Pioneer SA-7500 - zero bias on one channel - need help

    Finally, some good news! :banana: Yes, it was one of the driver transistor. I initially only tested them on base-emitter junction and it tested OK, and I did not know that the B-C junction should mirror the B-E. Thank you very much for the hint and helping me out here man, truly appreciated...
  14. M

    Pioneer SA-7500 - zero bias on one channel - need help

    Hi chazix, Thanks for the advice mate. I forgot to mention this in my original post, but I have already checked all the transistors (including driver and power) on the faulty channel using the junction check method. Both NPN and PNP types measure the voltage drop of roughly 0.6v on base-emitter...
Back
Top Bottom