Case #356461. Pioneer SX-626 receiver repair. Low, distorted and wobble sound.
Case from 07/06/2022.
Changing power supply filter capacitor 3300 uf solved the problem.
Case #356465. Sansui C-77 preamplifier repair.
Different output signal level in left and right channel . Unbalanced output signal .
Changing double front pot 100k ohm ” volume” solved the problem.
Cleaning did not helped.
One of them for some reason changed value to 60K ohm.
Case #456718. Technics SU-7600 amplifier repair. No sound.
06.11.2022. No sound on both channels.
Pilot light is ON.
Voltage -35 volt and +35 volt from power supply are present. All output transistors are ok.
Relay control transistor TR354 ( 2sc828a) replacement solved the problem.
Case #543645/ 09.12.2022 Luxman L-100 amplifier. Low sound from both channels.
Switch MODE/LEFT/RIGHT replacement solved the problem.
Repair case # 125432. Pioneer SA-9500II amplifier – no sound, keeps blowing main fuse.
4 Output transistors and main fuse replacement solved the issue.
Instead original transistors we installed MJE15032G / MJE15033G Transistors NPN/ PNP. Works even better then originals.( same terminals design, same configuration) . Main fuse- 4-6 Amp.
Case # 342553. Mcintosh 754 amplifier. Missing left channel. 09/27/2022
After troubleshooting found protection relay not working properly.
Relay replacement solved the problem.
Good- simplicity, simple schematic design, good sound, output driver boards separation, good ventilation.
Bad – missing power switch, no AC voltage filtration from electric outlet,any working device in same room with this model will affect sound quality.High electrical interference from 110 volt AC line.
Case# 456234.Pioneer SX-950. Protection relay not clicking.
Outputs -OK.All voltages from power supply – ok.
Replacing capacitors on power supply section and 2 resistors 1.3 kohm (green on picture) on protection control board solved the problem.
Good – perfect components separation and management on boards ,good ventilation, strong build chassis,realistic analog sound, used termo isolation holders and tubes on hard working parts, lowest possible AC line interference, stable output, sensitive tuner section,build to last.
Bad – high price.
Case #456343 10/09/2022 Sansui AU-919 . Goes to protection mode after 20-45 minutes.
After troubleshooting and testing found – 1 bad electrolytic capacitor 100mfx25v in preamp power supply section, 2 bad capacitors 100mfx35v on output driver board, 8 out of parameters non electrolytic caps on driver board, 2sf656 thyristor,leaking capacitor on protection board and relay control transistor.
This model emits a lot of heat even in normally working condition. Look like engineers focused on big output power and forgot about temperature balance inside.
Good – DC voltages separation from different source,big stable output power.
Bad – poor ventilation design. After 3-4 hours of work it turns to cooking pan for internal components. Most of them will handle it ,but not all of them.
Case # 657682. Luxman T-110U tuner. Low output from both channels.
Changed capacitors c290, c289,c286 and cleaned switch “muting off”.
Good – good and sensitive tuner, low signal distortion.
Bad – capacitor c290 on board located next to hard working,heat emitting resistor r315 and will dry capacitor over period of time. Components management failure.
————————————————————————————————————————————————— Case #746553 10/17/2022 . Victrola 65u vacuum tube radio/turn table from 1947 .No sound.
Replaced power supply dual section filter capacitor and 33 ohm buffer resistor.