1.4 ohm on primary winding Marantz 2285B

DreadPirate · 10th May 2008, 02:12 PM

This unit keeps blowing fuses. I'm starting a troubleshooting sequence, first step, I measure the primary resistance. I'm getting 1.4 ohm. From what I've read, anything lower than 2 ohm is questionable. Is this the cause of my overcurrent situation? I'm measuring 4 ohm on some of my other Marantzs...

Brett · 10th May 2008, 03:44 PM

If you are measuring with a typical DVM, then readings ubder a few ohms are far from accurate.

Otherwise, no idea sorry. I have a 2285B but mine has always worked fine.

jaycee · 10th May 2008, 03:48 PM

Disconnect the secondary windings from the circuit and power on with a light bulb in series with the live/hot wire. Make sure the secondaries arent touching anything (isolate them with tape). If the bulb lights, the transformers dead.

DreadPirate · 10th May 2008, 04:21 PM

Now I know why its nice to have the schematic... I followed the power to the output section and Marantz was good enough to provide a simple way to unplug the power to it. I pulled them both off and now the unit appears to power up, the filter caps charge and have voltage on them 52, -52 and I can hear the speaker relay click. There are two sets of two 2SD427 and 2SB557 per side and they are wire wrapped to terminals conveniently located for testing. These are original Marantz, will they be hard to find? Will I need to change them all (one set of 4 or the other)? Any chance some other fault is causing them to blow or do these just go out every once in a while?

djk · 11th May 2008, 08:37 AM

"Any chance some other fault is causing them to blow or do these just go out every once in a while?"

Yeah, every 30 years or so.

I would replace the drivers and outputs for both channels, and probably use the MJ21193/94 and MJE15030/31.

10th May 2008, 02:12 PM	#1
DreadPirate diyAudio Member Join Date: Jan 2006 Location: Northern Virginia, USA	1.4 ohm on primary winding Marantz 2285B This unit keeps blowing fuses. I'm starting a troubleshooting sequence, first step, I measure the primary resistance. I'm getting 1.4 ohm. From what I've read, anything lower than 2 ohm is questionable. Is this the cause of my overcurrent situation? I'm measuring 4 ohm on some of my other Marantzs...

11th May 2008, 08:37 AM	#5
djk diyAudio Member Join Date: Feb 2001 Location: USA	"Any chance some other fault is causing them to blow or do these just go out every once in a while?" Yeah, every 30 years or so. I would replace the drivers and outputs for both channels, and probably use the MJ21193/94 and MJE15030/31. __________________ Candidates for the Darwin Award should not read this author.

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10th May 2008, 03:44 PM	#2
Brett diyAudio Member Join Date: Jan 2002	If you are measuring with a typical DVM, then readings ubder a few ohms are far from accurate. Otherwise, no idea sorry. I have a 2285B but mine has always worked fine.

10th May 2008, 03:48 PM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Disconnect the secondary windings from the circuit and power on with a light bulb in series with the live/hot wire. Make sure the secondaries arent touching anything (isolate them with tape). If the bulb lights, the transformers dead.

10th May 2008, 04:21 PM	#4
DreadPirate diyAudio Member Join Date: Jan 2006 Location: Northern Virginia, USA	Now I know why its nice to have the schematic... I followed the power to the output section and Marantz was good enough to provide a simple way to unplug the power to it. I pulled them both off and now the unit appears to power up, the filter caps charge and have voltage on them 52, -52 and I can hear the speaker relay click. There are two sets of two 2SD427 and 2SB557 per side and they are wire wrapped to terminals conveniently located for testing. These are original Marantz, will they be hard to find? Will I need to change them all (one set of 4 or the other)? Any chance some other fault is causing them to blow or do these just go out every once in a while?

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