2sa1494 replacements ?

jackjackjs · 22nd May 2009, 09:44 AM

hi all ,
first time to post here.have some problem with amp and hope you guys can give me some advice .
i have a blew 2sa1494 and 2sc3858.i can't get the same at my town .the shopper tell me that 2sa1216 and 2sc2922 will be the same . after solder all the part,it looks and works fine.but it gets fairy hot very fast . i have no idea what's wrong and hope someone can help me it this .Thanks!!!

AndrewT · 22nd May 2009, 10:02 AM

Hi,
you probably have not checked and adjusted the output bias current.

If Vbe of the new devices is just slightly lower than the original devices then the output passes a lot more current and this results in much higher power dissipation and heatsink temperatures.

You need to find the set up instructions for the output stage and adjust to the correct values.

Don't use this modified/repaired amplifier until this is attended to properly.

jackjackjs · 23rd May 2009, 02:09 PM

Dear Andrew ,
thanks for the reply. can you explain more detail .because i am really new to diy.Thanks again!!!

AndrewT · 23rd May 2009, 04:19 PM

find or ask for the setup instructions.

22nd May 2009, 09:44 AM	#1
jackjackjs diyAudio Member Join Date: May 2009	2sa1494 replacements ? hi all , first time to post here.have some problem with amp and hope you guys can give me some advice . i have a blew 2sa1494 and 2sc3858.i can't get the same at my town .the shopper tell me that 2sa1216 and 2sc2922 will be the same . after solder all the part,it looks and works fine.but it gets fairy hot very fast . i have no idea what's wrong and hope someone can help me it this .Thanks!!!

22nd May 2009, 10:02 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, you probably have not checked and adjusted the output bias current. If Vbe of the new devices is just slightly lower than the original devices then the output passes a lot more current and this results in much higher power dissipation and heatsink temperatures. You need to find the set up instructions for the output stage and adjust to the correct values. Don't use this modified/repaired amplifier until this is attended to properly. __________________ regards Andrew T.

23rd May 2009, 04:19 PM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	find or ask for the setup instructions. __________________ regards Andrew T.

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23rd May 2009, 02:09 PM	#3
jackjackjs diyAudio Member Join Date: May 2009	Dear Andrew , thanks for the reply. can you explain more detail .because i am really new to diy.Thanks again!!!

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