Fault
Power on LED not illuminating
Intermittent loss of Audio and distortion

Common age-related issues

Power LED on the Display Board open circuit.
Blue clear LED 5mm x 2mm Rectangular Type 3V forward voltage installed fixing he issue.

Intermittent loss of Audio due to oxidised speaker switching contacts and dirty Volume control potentiometers.

Speaker protection relay replaced, 12 V DC Coil DP/CO 8 A contacts
Volume control potentiometers cleaned with De-Oxit ensuring noise free operation.

12 Volt and plus / minus 15 Volt power supplies repaired fixing the noise issue.

Following capacitors replaced

12 Volt supply
C407 47uF & C408 100uF 16V
Plus / Minus 15 Volt supply
C403 & C404 220uF 25V
Open Circuit or High ESR

Amplifier fully tested working correctly.

Additional tutorial videos

Alesis RA500
[ Ссылка ]

Alesis RA100
[ Ссылка ]

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