Lightning Struck AKAI Active Surround System Restored
MAKE AND MODEL: AKAI ACTIVE SURROUND SYSTEM/ACTIVE SUB-WOOFER MODEL SS-803-W
COMPLAINT REPORTED: Dead
PRELIMINARY WORK DONE: Opened the set, steps: Remove four screws from the front panel, gently take out the panel, inserting a flat screw driver underneath without causing damage to the plastic part. Remove four screws of the grill at the rear that projects out (bottom portion and not the top one, which is the woofer). Gently take it out. Remove the screws that hold the metal plate on to the cabinet. Gently insert a flat screw driver to detach it from the cabinet. Both the front and rear might have got stuck hard with the cabinet. So we need to pry these out.
Cleaned the set thoroughly using blower. Dismantled the front and back portions. Cut the black wire that is ground for the transformer outer shield, leaving a portion on the PCB for joining it later during re-assembly. The connectors to be removed are (1) AC input to the Transformer – 2pin located at AC input PCB (2) Transformer AC output to Main Board – 3 Pin (3) Two pin connector with white wires located at AC input PCB, that go to front panel for the Mains on-off switch (4) Two black wires that go to main volume control pot in front panel – 2 pin (5) Two pin connector – Red and black – that goes to Woofer (6) 11 Pin connector that goes to front panel. Slid out the cables that go to the front panel through a hole provided in the inner frame. Once again cleaned all the boards and hard to reach portions thoroughly.
VISUAL INSPECTION: Fuse was found blown. Looked for any bulgy or leaked capacitors, burst parts etc. As the soldering sides of the PCBs were having left over flux that had got hardened and become dark, used a metal brush and cleaned all these neatly. Noticed a track cut in the ground of LED power indicator, in the front panel board. This track was next to the AC input, and lightning could only be the source which would have cut the track due to high voltage arcing. There were a lot of dry solder joints to such an extent that the tips got loosened when I cleaned the board.
TROUBLESHOOTING AND RECTIFICATION DONE: Checked for any shorts of semiconductors using Analogue Multimeter, keeping it in X1 Range, as advised by Jestine Yong in his book ‘Testing Electronic Components.’ (https://www.testingelectroniccomponents.com/) Did not find any short or leak in the output transistors and diodes. The ESR of the caps showed way out of range. Replaced all the electrolytic capacitors on the main board and the front panel board, which had the pre-amp ICS in it. Looked for any other track cuts. Retouched all the solder joints on both the boards. Joined the cut track by a wire. Cleaned the boards thoroughly using IPA. Allowed the board to get dried up fully. Lubricated the connectors using switch cleaning oil. Cleaned the Main volume, bass, treble and Rear speaker volume controls and lubricated. Covered the 230V AC tracks on the front panel with a few layers of plastic tapes to avoid accidental touching by hand (preventing a possibility of articles coming from me cut off permanently! (LOL)) Connected the boards, Mains Transformer and Woofer, speakers, audio input and applied power. Slowly increased the mains volume and got the output. The system was working very well without any distortion even at full volume. The controls also turned smoothly without causing any noise. After ensuring that the set worked well for a long time, switched off power, dismantled the boards and refit it back into its cabinet, joining the ground wire back to the TX, duly putting a sleeve to avoid its touching any other hot spots. Once again tried it for several hours before calling the customer (who happened to be my school classmate) to come and pick it up. Luckily, this set not only survived a lightning attack, but also lived up to undergo a total rework! Job satisfaction, of-course, was more than happy to jump itself to join the comrades!
HERE ARE A FEW PICTURES: (The purposeful comments are to provide some humor!)
This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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