Year: 2023

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Case 756577. GAS THALIA Servo Loop Preamplifier. Unit has damaged “OUTPUT” plug.

Problem solved by OUTPUT PLUG REPLACEMENT.
Technical design review.
Pluses- simplicity, build simple as possible. Minimum wires used in design . Servo loop channel method ( input signal controlled by output signal) realized in schematic. This method has own advantages and minuses. Some called it “over kill” and unnecessary, some – perfect and high performance support method. Elimination input electrolytic capacitor in signal path is questionable. Debates in process already for over 30 years. Still unique .
Low power unit use for functioning. Good detailed attention to phono input section.


Minuses- no ventilation holes, using no soldering contacts on major transistors ( oxidation )
Power supply filter capacitors installed close to heat emitting heat sink ( heat destroy electrolytic ), not shielded balance pot wires.

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Case 254532 . Harmon Kardon PM665 amplifier. Intermittent sound on /off.

After troubleshooting found few cracked soldering joints on preamplifier and tone control board.
Problem solved by re-soldering bad joints.

Nice amplifier. Good sound performance.
Technical review .
Pluses – this amp has own character in technical design . Complete power DC source separation for each channel. Independent power transformer for each channel gives you stability. Speakers Protection realized on soft start, self control and sound time delay idea.

Minuses – high concentration of heat emitting components in some areas.Some areas on PCB boards overheating and damaging soldering joints after time .

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Case 223126. Pioneer SX-1250 receiver . Unit does not turn on. 02/20/2023

After troubleshooting found not working power switch.
Problem solved by replacement.LED lamps installed.( picture 5)
Technical review. (picture 8)
This model belongs to “King family” of receivers and one of the best receivers human kind ever build. This model was a legend and will be a legend for long time .
Pluses
1.Has 3 separate protection circuits ( fuses + termofuse , soft start relay and protection relay).
2. Build to last long, long, long time.
3. Top line of electronic components used in manufacturing process.
4. Shielded tuner area, power transformer and shielded important signal path line.(pictures 1,2 )
5. Perfect wires management inside.(picture 3 )
6. Spark and AC line interference solved perfect in design.
7. Perfect components management on boards.
8. Perfect temperature balance by using huge heat sink in output section.
9. Real analog sound . Huge power . All sound parameters tested and found as stated in manual .Not so many units can do that.
10. Wires and heat emitting resistors have termo protection isolation tubes in hot areas.Good ventilation design.( pictures 6 , 7 )
11. High quality metal used on contacts ( bolts on power supply capacitors).
12. Short as possible signal wires.
13. Minimum use of life limited parts and components.
14. Easy to operate , service and work inside.
15. Good sensitive tuner for 1979.
Minuses
We have not found one.
On last 3 pictures we present modern ” high technology and fancy” audio electronics design from 2000-2022. We called it ” Glue technology ” . After while all this glue on boards turns to unexpected carbon resistors in your schematic and start destroying your unit. Just compare and you will know why analog vintage audio is better few times then most modern audio equipment by quality and performance.