Category: Blog

Speakers on this model you can use any modern  4 Ohm , 8 Ohm or 16 Ohm. Power  12VDC. Audio out power up to 10 W. Antenna must be connected  or imitated by simple wire.  Multi section electrolytic aluminum capacitor need to be replaced in any case.   All tubes  tested   and found OK.  Output transistor DS-503 is  defective and need replacement . Indication of bad output transistor  – burned resistor 44   on circuit board  0.33 ohm  ( emitter line )  .   After experimenting we use  modern 2SA1265N  as a replacement.  No changes or adjustment needed.  Transistor body type is different but it is no big deal  for handy person.

Case #  769877  .    03.27.2026  . Adcom GFA555 ii amplifier. Missing left channel.

Interesting case.  Fuse – ok, right channel is ok.    82 volt DC on the left channel speakers plugs.  Speaker start smoking.  Powerful amp for someone who loves power.

Most Adcom amplifiers don’t have a protection circuit in the schematics, so the results are standard. If something happens, speakers take a direct hit from the amp’s output section.  This case is interesting because even after issues like that, all output transistors are still alive, meaning good-quality components were used. Found a bad driver transistor  2SA1210 on the input/driver  board.  We changed all  input and driver transistors  and plus 8 pin Opamp IC  . Channel starts working, but   DC OFFSET is more than 2 volts, and it is not good. Bias not in range also.  All new parts we used were purchased online.  Finally , after couple more hours of troubleshooting we found that the new IC  LT1006   we purchased online is bad. Next time, we’d better use new old stock parts,  we trust them more than new production. Bad IC,S on the last image.

CASE  # 197856. JANUARY 21, 2026 . SANSUI AU-517 AMPLIFIER. CRACKLING, POPPING SOUND IN LEFT CHANNEL.

Nice  amplifier.  Build to last long time.  Ventilation , sectional construction , not overloaded schematic, good protection circuit  ,  shielded boards by metal covers ., good components management on boards ( no electrolytic capacitors close to heat-emitting components.

Classic case for troubleshooting to the component level.  No nonsense, massive components change.    Cleaning front controls and boards, dusting, testing voltages from the power supply, vibration test,  soldering joints refreshment. Capacitors ESR  test – bad replaced. ( not many found out of parameters)  .   PROBLEM IS STILL THERE.   Focused on the left channel output board.  After applying heat to small signal transistors in working mode, crackling starts intensify ( 1 -3 seconds touch  soldering  gun to the plastic body of transistor  ) . BINGO.  Replaced 2 small transistors 2SA750 – problem solved. Tested DC offset voltage on both channels  – ok.