Yamaha B2 P/S

eyoung · 11:51 PM

Hola Y'all,

I hate to admit it but I screwed up and shorted out my 12v ps while trying to figure out a VU meter problem and toasted the 12v side. This power supply has more transistors than most amplifiers. That being said I have been able to source all the affected transistors, my question is i have a 13v 500ma zener that I do not have and wonder can I use a 12v zener and fiddle with resistor to mget my 12.8v at the base of TR213/ zener is d210. I have attached the schematic (ps only as the whole thing is gynormous)

Your input is valued, Elwood

eyoung · 29th September 2009, 01:30 AM

whoops...

my schematic did not load... let us try again.

E

jaycee · 29th September 2009, 06:25 AM

in practice the slightly lower voltage by just using a 12v zener should make no difference to operation at all.

h_a · 30th September 2009, 03:20 PM

Hi Elwood,

from a short look d210 is the rail voltage reference, if you use a lower zener you get a lower rail. You cannot adjust it with the resistor, as the Zener goes directly to the base.

Have fun, Hannes

Limhes · 30th September 2009, 03:29 PM

Or you could place one or two diodes in series with the zener..

eyoung · 18th October 2009, 08:32 PM

Hola Y'all...

as I am still thinking and collecting parts to repair my P/S there is a transistor that is no longer available , TR214 see previous post for schematic it is a 2sc789 and I am looking for a subtitute my best guess is either a TIP31c or a BD139 both readily available from Mouser or Digikey any thoughts on the subject would be apreciated...

As I humbly Remain, Elwood

Bigred · 19th October 2009, 09:28 AM

Yup, TIP31 "B" or "C" will do the job.

eyoung · 19th October 2009, 11:37 PM

Hola again Y'all...

Thanks for the input, as they are cheap I may buy some of both. I'll keep Y'all
posted..

Thanks a heap, Elwood

EchoWars · 12:29 AM

If you want to keep that thing alive, get in there are replace all those horrid 2SC458 leaksistors in the +/-85V regulated supply (which the VFET's need to stay alive). I generally use Fairchild KSC945L's, but there's lots of good subs for the C458, such as the Panasonic 2SC1509S.

If the meter(s) go whacky, know up-front that it's full of those C458's.

eyoung · 20th October 2009, 01:54 AM

Echo Wars ,

Thats just the kind of info I was looking for.

Thanks a Heap,

Elwood

28th September 2009, 11:50 PM	#1
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	Yamaha B2 P/S Hola Y'all, I hate to admit it but I screwed up and shorted out my 12v ps while trying to figure out a VU meter problem and toasted the 12v side. This power supply has more transistors than most amplifiers. That being said I have been able to source all the affected transistors, my question is i have a 13v 500ma zener that I do not have and wonder can I use a 12v zener and fiddle with resistor to mget my 12.8v at the base of TR213/ zener is d210. I have attached the schematic (ps only as the whole thing is gynormous) Your input is valued, Elwood __________________ "when you open your mind to the imposible, soon you will find the truth...." Last edited by eyoung; 28th September 2009 at 11:51 PM. Reason: my schematic did not load

19th October 2009, 11:37 PM	#8
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	Hola again Y'all... Thanks for the input, as they are cheap I may buy some of both. I'll keep Y'all posted.. Thanks a heap, Elwood __________________ "when you open your mind to the imposible, soon you will find the truth...."

20th October 2009, 12:26 AM	#9
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	If you want to keep that thing alive, get in there are replace all those horrid 2SC458 leaksistors in the +/-85V regulated supply (which the VFET's need to stay alive). I generally use Fairchild KSC945L's, but there's lots of good subs for the C458, such as the Panasonic 2SC1509S. If the meter(s) go whacky, know up-front that it's full of those C458's. Last edited by EchoWars; 20th October 2009 at 12:29 AM.

20th October 2009, 01:54 AM	#10
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	Echo Wars , Thats just the kind of info I was looking for. Thanks a Heap, Elwood __________________ "when you open your mind to the imposible, soon you will find the truth...."

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29th September 2009, 06:25 AM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	in practice the slightly lower voltage by just using a 12v zener should make no difference to operation at all.

30th September 2009, 03:20 PM	#4
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Hi Elwood, from a short look d210 is the rail voltage reference, if you use a lower zener you get a lower rail. You cannot adjust it with the resistor, as the Zener goes directly to the base. Have fun, Hannes

30th September 2009, 03:29 PM	#5
Limhes diyAudio Member Join Date: Apr 2005 Location: Nijmegen!	Or you could place one or two diodes in series with the zener..

19th October 2009, 09:28 AM	#7
Bigred diyAudio Member Join Date: Jul 2007	Yup, TIP31 "B" or "C" will do the job.

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