Sansui BA 5000 Loud pop at turn on / off

VintagePlus · 20th December 2011, 03:14 AM

I recently acquired a Sansui BA 5000 which works good except when powering on jusrt before the soft start relay engages there is a loud pop through the speakers. The same when powering off. The dc at the speaker terminals jumps to over 100mv when it does ghis and instantly settles back to 11 mv. I am new here but see you all giving great advice so figured i would give it a try.

VintagePlus · 20th December 2011, 09:56 PM

Anybody?

amptech · 05:34 PM

Welcome vintageplus, all the soft start is doing is slowing down the high in rush to the main transformer, this simple circuit uses a high watt resistor and a relay that click's in after a second or so thus shorting out the inrush resistor..

if there is space within the amp you could add a speaker protection circuit with latching relay activation, and it will save that loud on and off pop... One thing, have you checked the power supply capacitors has sometimes these can be leaky..

the low 10mv offset is normal and I've seen many amps jump high with that same old pop then ease in after a second or so..
some peavey, h/h amps did that pop! tweeters don't like that loud pop and it also bumps the bass woofer out also.

amptech · 21st December 2011, 05:31 PM

do you have schematic for this amp??

VintagePlus · 21st December 2011, 07:12 PM

Thanks amptech! I am going to be recapping the power supply in the next couple days. I will see if that helps. Yep i do have the schematic.

ilimzn · 21st December 2011, 09:30 PM

This issue will have to be rectified as the amp uses auto-transformers on the output, and this setup does not like DC on the output AT ALL. You may have a leaky coupling cap somewhere... IIRC the BA5000 uses a sort of pre-amp or buffer in front of it's power amp section. This may be the place to look. Also, does it have a relay in front of the autoformer?

amptech · 21st December 2011, 09:56 PM

vintageplus, if you could post schematic on here we're take a look and track this fault.

regards.

tomtt · 21st December 2011, 10:04 PM

contact cleaner

VintagePlus · 21st December 2011, 10:38 PM

Where should i use that? I have already drilled the pots and cleaned the controls.

VintagePlus · 21st December 2011, 10:41 PM

I will post the schematic tonight. Thanks for the help so far.

20th December 2011, 03:14 AM	#1
VintagePlus diyAudio Member Join Date: Dec 2011 Location: BC Canada	Sansui BA 5000 Loud pop at turn on / off I recently acquired a Sansui BA 5000 which works good except when powering on jusrt before the soft start relay engages there is a loud pop through the speakers. The same when powering off. The dc at the speaker terminals jumps to over 100mv when it does ghis and instantly settles back to 11 mv. I am new here but see you all giving great advice so figured i would give it a try.

21st December 2011, 05:28 PM	#3
amptech diyAudio Member Join Date: Jan 2009 Location: Glasgow	Welcome vintageplus, all the soft start is doing is slowing down the high in rush to the main transformer, this simple circuit uses a high watt resistor and a relay that click's in after a second or so thus shorting out the inrush resistor.. if there is space within the amp you could add a speaker protection circuit with latching relay activation, and it will save that loud on and off pop... One thing, have you checked the power supply capacitors has sometimes these can be leaky.. the low 10mv offset is normal and I've seen many amps jump high with that same old pop then ease in after a second or so.. some peavey, h/h amps did that pop! tweeters don't like that loud pop and it also bumps the bass woofer out also. Last edited by amptech; 21st December 2011 at 05:34 PM.

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20th December 2011, 09:56 PM	#2
VintagePlus diyAudio Member Join Date: Dec 2011 Location: BC Canada	Anybody?

21st December 2011, 05:31 PM	#4
amptech diyAudio Member Join Date: Jan 2009 Location: Glasgow	do you have schematic for this amp??

21st December 2011, 07:12 PM	#5
VintagePlus diyAudio Member Join Date: Dec 2011 Location: BC Canada	Thanks amptech! I am going to be recapping the power supply in the next couple days. I will see if that helps. Yep i do have the schematic.

21st December 2011, 09:30 PM	#6
ilimzn diyAudio Member Join Date: Feb 2005 Location: Zagreb	This issue will have to be rectified as the amp uses auto-transformers on the output, and this setup does not like DC on the output AT ALL. You may have a leaky coupling cap somewhere... IIRC the BA5000 uses a sort of pre-amp or buffer in front of it's power amp section. This may be the place to look. Also, does it have a relay in front of the autoformer?

21st December 2011, 09:56 PM	#7
amptech diyAudio Member Join Date: Jan 2009 Location: Glasgow	vintageplus, if you could post schematic on here we're take a look and track this fault. regards.

21st December 2011, 10:04 PM	#8
tomtt diyAudio Member Join Date: Aug 2002 Location: kansas city mo, and on occasion, around the world ... Blog Entries: 15	contact cleaner

21st December 2011, 10:38 PM	#9
VintagePlus diyAudio Member Join Date: Dec 2011 Location: BC Canada	Where should i use that? I have already drilled the pots and cleaned the controls.

21st December 2011, 10:41 PM	#10
VintagePlus diyAudio Member Join Date: Dec 2011 Location: BC Canada	I will post the schematic tonight. Thanks for the help so far.

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