Transformer / Help .

funky2x · 23rd July 2008, 05:28 PM

Hello Guys
could help me to figure what the transformer volts should be .
the schematic taken from Philips powered subwoofer and they dont mentioned about the transformer at what volts to use to power the the two power transistores 2SC and 2SA replaced with BD245 / BD246.
thanks

Eva · 24th July 2008, 06:42 PM

Supply rails in the original design were probably in the +/-50V to +/-60V range.

However, BD245 and BD246 are not good replacements. With this transistor choice, rails should not exceed +/-45V and this is providing that the speaker is 8 ohms because they will have trouble handling 4 ohms unless voltage is further reduced.

It would be useful to know voice coil resistance. Consider finding better replacement transistors too.

funky2x · 25th July 2008, 12:04 AM

BD245/BD246 that what VRT-DISK first choice as replacement .
Used +/-35 volts to power the circuit and think am having problem with the components here , cus no sound at the output .
the Relay wont left On .
thank you for your replay and your help .
but could you tell me what the best choice as replacement ?
Thanks

Eva · 25th July 2008, 11:23 AM

Ask in the solid state forum about stronger replacements for 2SA1941 and 2SC5198 and you will get an avalanche of suggestions. Beware of fakes.

The relay may be not acting because 35V is too low. Check that Q501 and Q502 are conducting. The current provided by the 1K 2W resistor (R525) may not be enough.

You would get many replies if you asked some moderator to move this thread to the solid state furm.

23rd July 2008, 05:28 PM	#1
funky2x diyAudio Member Join Date: Jan 2008	Transformer / Help . Hello Guys could help me to figure what the transformer volts should be . the schematic taken from Philips powered subwoofer and they dont mentioned about the transformer at what volts to use to power the the two power transistores 2SC and 2SA replaced with BD245 / BD246. thanks

24th July 2008, 06:42 PM	#2
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	Supply rails in the original design were probably in the +/-50V to +/-60V range. However, BD245 and BD246 are not good replacements. With this transistor choice, rails should not exceed +/-45V and this is providing that the speaker is 8 ohms because they will have trouble handling 4 ohms unless voltage is further reduced. It would be useful to know voice coil resistance. Consider finding better replacement transistors too. __________________ I use to feel like the small child in The Emperor's New Clothes tale

25th July 2008, 11:23 AM	#4
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	Ask in the solid state forum about stronger replacements for 2SA1941 and 2SC5198 and you will get an avalanche of suggestions. Beware of fakes. The relay may be not acting because 35V is too low. Check that Q501 and Q502 are conducting. The current provided by the 1K 2W resistor (R525) may not be enough. You would get many replies if you asked some moderator to move this thread to the solid state furm. __________________ I use to feel like the small child in The Emperor's New Clothes tale

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25th July 2008, 12:04 AM	#3
funky2x diyAudio Member Join Date: Jan 2008	BD245/BD246 that what VRT-DISK first choice as replacement . Used +/-35 volts to power the circuit and think am having problem with the components here , cus no sound at the output . the Relay wont left On . thank you for your replay and your help . but could you tell me what the best choice as replacement ? Thanks

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