Nakamichi Stasis PA-5E MkII

EspenE · 5th October 2010, 08:15 PM

I have a Nakamichi PA-5E MkII.
The mains power fuse blows the second I switch the amplifier on.

I cannot see anything wrong inside the amp: no burned components, no appearent cold solder joints.

Do anyone have any idea on how I should proceed on this?

Thanks, Espen

VHF man · 6th October 2010, 12:10 AM

If there are internal fuses on the +/- rails for each channel then replace them with 10W 47-100 ohm resistors - on both channels. That will allow you to measure and compare quiescent currents. If the mains fuse still blows then you probably have a short cct bridge rectifier. You should be able to check the BR's in cct with a DMM.

A blown bridge is pretty common with an old amp.

stratus46 · 6th October 2010, 03:18 AM

Quote:

Originally Posted by VHF man

If there are internal fuses on the +/- rails for each channel then replace them with 10W 47-100 ohm resistors - on both channels. That will allow you to measure and compare quiescent currents. If the mains fuse still blows then you probably have a short cct bridge rectifier. You should be able to check the BR's in cct with a DMM.

A blown bridge is pretty common with an old amp.

Really? I find that to be a pretty rare failure - at least in the US.

G²

Trevor White · 6th October 2010, 06:34 AM

Quote:

Originally Posted by EspenE

I have a Nakamichi PA-5E MkII.
The mains power fuse blows the second I switch the amplifier on.

I cannot see anything wrong inside the amp: no burned components, no appearent cold solder joints.

Do anyone have any idea on how I should proceed on this?

Thanks, Espen

Could be

The mains transformer,
Shorted bridge or diodes,
Shorted output transistors,
shorted filter caps (usually quite rare),

regards
Trev

5th October 2010, 08:15 PM	#1
EspenE diyAudio Member Join Date: Jun 2003 Location: Oslo	Nakamichi Stasis PA-5E MkII I have a Nakamichi PA-5E MkII. The mains power fuse blows the second I switch the amplifier on. I cannot see anything wrong inside the amp: no burned components, no appearent cold solder joints. Do anyone have any idea on how I should proceed on this? Thanks, Espen

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6th October 2010, 12:10 AM	#2
VHF man diyAudio Member Join Date: May 2007	If there are internal fuses on the +/- rails for each channel then replace them with 10W 47-100 ohm resistors - on both channels. That will allow you to measure and compare quiescent currents. If the mains fuse still blows then you probably have a short cct bridge rectifier. You should be able to check the BR's in cct with a DMM. A blown bridge is pretty common with an old amp.

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