1

Score

Avatar
Rob
13

Asked

Power Supply, Overheating components, Voltages Out Of Spec.

History

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.

Edited by: Sam Lionheart ( ) , Rob ( )

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.

Dave,

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

Dave,

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???

Dave,

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.

Rob,

Show 2 more comments

Post Answer

1

Score

Avatar
Jaybird2005
185

Answered

PermalinkHistory

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.

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

Dave,

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

Jaybird2005,

Wow, you assumed 60 hz, and I assumed 110v... Doh - both right! I think his English convinced me...

Dave,

Add Your Answer

View Statistics:

Today: 0

This Week: 0

This Month: 11

All Time: 2,033