Hi guys,
I've had several amps in a row which had enabled TL494 protection or not engaging the relay's due tue a voltage offset on the secondary GND (- speaker terminal).
After tracing the whole protection circuit of the amp looking for clues, it happens often that a single good reading resistor or capacitor connected to secondary GND makes the amp to go in protect. Grounding the secondary GND to the main GND with a 10k-1k resistor can mostly take the amplifier out of protect when I measure an offset.
The amplifiers are then working properly and nothing heats up or anything.
Do you guys also have the same defect sometimes? What can cause the secondary GND to have offset?
I've had several amps in a row which had enabled TL494 protection or not engaging the relay's due tue a voltage offset on the secondary GND (- speaker terminal).
After tracing the whole protection circuit of the amp looking for clues, it happens often that a single good reading resistor or capacitor connected to secondary GND makes the amp to go in protect. Grounding the secondary GND to the main GND with a 10k-1k resistor can mostly take the amplifier out of protect when I measure an offset.
The amplifiers are then working properly and nothing heats up or anything.
Do you guys also have the same defect sometimes? What can cause the secondary GND to have offset?
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There are VERY few amplifiers that have complete isolation between the primary and secondary grounds. Most have a 1k ohm resistor between the primary and secondary grounds.
For significant offset (especially one that has ~12v and can cause excessive current flow) a shorted transformer (primary to secondary) is often to blame.
Other offset can be caused by circuits that are connected to both the primary and the secondary circuits. These can include the protection and muting circuits. Having an open resistor that's between the grounds can prevent the amp to work properly because these circuits are passing a small current between the primary and secondary grounds.
For significant offset (especially one that has ~12v and can cause excessive current flow) a shorted transformer (primary to secondary) is often to blame.
Other offset can be caused by circuits that are connected to both the primary and the secondary circuits. These can include the protection and muting circuits. Having an open resistor that's between the grounds can prevent the amp to work properly because these circuits are passing a small current between the primary and secondary grounds.
So you mean this "single good reading R or C " is defect or making no connection due to broken /burned traces etc?