Orion 2250sx

[RockfordFIx]

Rca shields to positive = 2.8mohm
There is a square wave but it distorts as the transformers begin hissing. Can i remove the rail voltage wires to the audio board tobe sure it's not the audio portion? All the audio outputs checked out fine.

 

[RockfordFIx]

I removed the rail voltage wires both sides one at a time from the audio board just in case the audio portion was casing stress on tje powersupply. No change, I can power the amp for about 45 secs while it's hissing and the outputs heat up. At this point I need to remove the board

 

[Perry Babin]

This may be due to the under-sized replacement caps.

 

[RockfordFIx]

Since ordered caps I ordered a tl494cn ic and optocouplers. Replaced them as I replaced the caps. Amp powers up and still hissing. Have square wave but is a bit fuzzy probably due to transformer hissing. Have rail voltage. But NOW the power LED does not power on. Does power LED switch from the tl494?

 

[Perry Babin]

The LED probably gets power from the +15v regulator that feeds pin 8 of the op-amps.

The hissing is likely from the regulators acting too quickly. The the fuzziness related to amplitude or pulse width?

 

[RockfordFIx]

Okay I will check that next. I am installing the rail voltage wires. Had to replace them cause the old wire was oxidized and would tin.

 

[RockfordFIx]

I am confused.... after installing the rail voltage wires the power LED is on and the powersupply is not hissing. Just clamped the board and is playing audio 3/4 volume. This is a very clean sounding amp

 

[Perry Babin]

If the rail caps are out of circuit with the wires disconnected, that could allow the regulator to operate too quickly. The rail caps would damp the response and stop the noise.