Rotel RA-02 Amplifier Repair (With Audio Tutorial)

Fault 1
Amplifier in protection Mode
Right channel failure.
Fault 2
Input selection erratic.
Fault 3 Brown corrosive / conductive Glue issue.
Fault 4 Rear speaker binding posts damaged.
Fault 1
Right channel Audio Output Transistors short circuit.
Other components checked and found to be defective.
Components Replaced
Resistors
R622 47 Ohm ¼ Watt
R628 220 Ohm ¼ Watt
R630, R632 0.22 Ohm 3 Watt
Transistors
Q612 2SC1941
Q618 2SB631K
Q614, Q616 2SD600K
Q620 2SD1057 Sanyo
Q622 2SB817 Sanyo
Bias for each channel set to 4 millivolts.
Fault 2
Input selection switch / encoder removed and taken apart.
Contacts cleaned with a fibre glass pencil and De-Oxit to remove all dried grease and oxidisation, fixing the erratic input selection issue.
Fault 3
Brown Glue from the plus / minus 18V power supply section removed and
2 x 18V 500mW Zener Diodes replaced.
Glue also removed from other power sections of the Amplifier.
Fault 4
Damaged speaker Binding posts replaced.
User controls and switches cleaned with De-Oxit to ensure noise free operation.
Speaker protection relays 3 x 24 V DC Coil DP/ST replaced to avoid any future issues of low-level distortion or intermittent sound loss due to worn and oxidised switching contacts.
DC off set checked on both channels low at 6 -7 millivolts.
Amplifier fully tested working correctly.
Bulb current limiter / Dim Bulb tester.
• Light Bulb Current Lim...
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[@izzzzzz6]

Your videos are extremely informative now that you have added audio and step by step processes. Thanks again.

[@AudioAmplifierServicing]

Thank you

[@chrissmith7069]

Excellent tutorial Gary! 👌

[@AudioAmplifierServicing]

Chris thank you

[@jerrymarquez710]

Where do u recommend buying pairs of output transistors?
It seems digi key or mouser tend to have minimums.. i had to buy 10 at a time to fix bass amp ($60 with shipping for 4 transistors) and digikey just had a 297 or do minimum! ($300)Ha
Where do u recommend to avoid counterfeit?
P.S.
yours are among the very best repair videos I’ve seen…beautifully clear detailed, thorough and to the point . Thx!

[@AudioAmplifierServicing]

Hi the issue is ensuring that smaller companies are indeed supplying genuine originals. It's not easy and although the likes of Mouser and Digikey are often on the face of it more expensive at least you know what your receiving components that will work.
For components that are current I always use Mouser and Digikey but of course buy in bulk to lower cost and for obsolete components I use one or two selected suppliers.