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Power Supply, Overheating components, Voltages Out Of Spec.

The power supply in my Marantz SR-92 Receiver is way out of spec, I need to figure out why, at the 20v side iam getting 30 volts at the 24 volt side iam getting 28 volts, this is causing a mosfet to cook and it is also causing 4 transistors to cook, ive replaced them, it works but they get scary hot, I replaced 2 ceramic disc caps on the psu along with a resistor, This model is a exact twin of the Carver 895 receiver, Please help. This IS one a regular 120 volt ac line.

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The high voltage tag should be reserved for >110V. I understand that the voltage in your power supply is high, but that tag means "Above normal mains voltage". Typically 400V+, like you find on most US Navy equipment.

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You have either a zener diode out of spec, or a resistor out of spec. Without a schematic it is nearly hopeless.

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Is the SR-92 the same as the SR9200?

These guys will sell you the Service Manual for the Marantz SR9200 for $20 in PDF format. That includes the Electronics Schematic(s). Just schematics runs $15

http://www.manualsparadise.com/ShowProdu...

Make a note of the Service Bulletins, including the Firmware Upgrade! They might also be worth having to keep your antique tuner/amp in top condition.

Where are the schematics on ifixit.com???

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There is no firmware on this, its not the same as the 9200, A Carver 895 is identical, I do have a service manual for it , i nearly replaced everything on the psu circut board and iam still having issues.

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Any chance of finding a schematic?

There would not be a 110v/220v switch that might be in the wrong position? (I had to ask).

I am guessing you are not hearing a 60Hz hum, so it is probably not a filter cap. See if there is a reference zener (looks like a diode). It may be labeled CRx or ZNx, VRx or Vrefx. These are available in many values, but are only stable in certain values (that's Physics for you - only partly stable). If the reference is bad the output would only go a few volts high or low which should produce that symptom.

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The 110/220 volt switch in the wrong position would result in a low voltage, not a high voltage

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It was not specified whether the unit is connected to 110v or 220v. If it were connected to 220v with the switch on 110v......

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Wow, you assumed 60 hz, and I assumed 110v...

Doh - both right!

I think his English convinced me...

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Rob will be eternally grateful.
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