reducing voltage - Page 3

djk · 15th January 2009, 09:25 PM

"on semi MJ15015-16 diferent case but very reliable "

Requires driver transistors as these are not Darlington.

wakibaki · 15th January 2009, 09:53 PM

An easy way to drop a volt or so is to use 2 or more series diodes in each limb of your rectifier.

This is not to say that there is no other impact, but in most instances it will be negligible.

The cure probably lies elsewhere in this case tho'.

w

wg_ski · 15th January 2009, 10:06 PM

Quote:

Originally posted by rtill
here's the schematic....supposedly 200 watts, is this possible?

100 watts at 4 ohms with realistic power supply drop. Two channels makes 200.

Quote:

I have had a few issues since 1st posting. The tip142 wasn't secured properly, got too hot and exploded. Replaced it and now it blows fuses once it is turned on. What would cause this? I would imagine something else in the circuit is blown to now cause the fuses to blow.

The TIP147 is probably shorted as well. If you blow one replace them both. It might not have been your fault - TIP142/147 devices are often faked.

wg_ski · 15th January 2009, 10:09 PM

Quote:

Originally posted by djk
"on semi MJ15015-16 diferent case but very reliable "

Requires driver transistors as these are not Darlington.

Requires a TIP142/147 pair as drivers.

djk · 16th January 2009, 02:03 AM

I would use TIP41/42C as drivers, or MJE15030/31.

This circuit will run fine on +/-42V, don't bother trying to lower the voltage.

Mitch Alsup · 16th January 2009, 04:21 AM

This circuit is very similar to the Dynaco 150*. Excepting a current source on the dif-amp, and a current srouce in the VAS, and the Darlington outputs.

(*) And numerous others.

sakis · 16th January 2009, 08:00 AM

Quote:

Originally posted by djk
"on semi MJ15015-16 diferent case but very reliable "

Requires driver transistors as these are not Darlington.

my mistake thanks djk

it was supposed to be 11015-16 .....and this is a direct replacement

sorry for the confusion and thanks for waking me up djk .....

AndrewT · 16th January 2009, 01:16 PM

Hi,
poor choice of component values and topology in that schematic.
Bias pot is wired that could cause overheating, ratio of R9/7 is wrong, if current limit triggers then T3 will probably blow, no diodes to limit inductive peaks when protection triggers, what does the R3=3k3 do as a bootstrap? signal and power grounds are mixed together.

wg_ski · 16th January 2009, 02:45 PM

Darlingtons typically have the damper diodes built in. Go discrete and you need them. The whole idea of this circuit is the minumum # of parts.

As far as mixing power and signal grounds, LVS wouldn't care. It's the builder's responsibility to separate them if he wants maximum performance.

15th January 2009, 09:25 PM	#21
djk diyAudio Member Join Date: Feb 2001 Location: USA	"on semi MJ15015-16 diferent case but very reliable " Requires driver transistors as these are not Darlington. __________________ Candidates for the Darwin Award should not read this author.

16th January 2009, 02:03 AM	#25
djk diyAudio Member Join Date: Feb 2001 Location: USA	I would use TIP41/42C as drivers, or MJE15030/31. This circuit will run fine on +/-42V, don't bother trying to lower the voltage. __________________ Candidates for the Darwin Award should not read this author.

16th January 2009, 01:16 PM	#28
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, poor choice of component values and topology in that schematic. Bias pot is wired that could cause overheating, ratio of R9/7 is wrong, if current limit triggers then T3 will probably blow, no diodes to limit inductive peaks when protection triggers, what does the R3=3k3 do as a bootstrap? signal and power grounds are mixed together. __________________ regards Andrew T.

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15th January 2009, 09:53 PM	#22
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	An easy way to drop a volt or so is to use 2 or more series diodes in each limb of your rectifier. This is not to say that there is no other impact, but in most instances it will be negligible. The cure probably lies elsewhere in this case tho'. w

16th January 2009, 04:21 AM	#26
Mitch Alsup diyAudio Member Join Date: Aug 2007	This circuit is very similar to the Dynaco 150. Excepting a current source on the dif-amp, and a current srouce in the VAS, and the Darlington outputs. () And numerous others.

16th January 2009, 02:45 PM	#29
wg_ski diyAudio Member Join Date: Oct 2007	Darlingtons typically have the damper diodes built in. Go discrete and you need them. The whole idea of this circuit is the minumum # of parts. As far as mixing power and signal grounds, LVS wouldn't care. It's the builder's responsibility to separate them if he wants maximum performance.

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