Question about weird diode arrangment

substrate · 27th April 2006, 11:49 PM

I have a question regarding the following schematic (for a Fender guitar amp):

http://www.st-andrews.ac.uk/~jcgl/Sc...oax/page6.html

If you look at the upper-left corner of the schematic you'll see two branches with three diodes in series. I was wondering what the purpose is of having these three diodes in series like that, and also why they have the markings on the diodes "-" then "+" instead of the other way around? With a typical diode, wouldn't you indicate the "+" on the anode (non-stripe) and "-" on the cathode (stripe)?

Me thinks that it's to drop the voltage, but the voltage is so high that I don't imagine that you'd get significant drop across the diodes.

Thanks for any input.

-Brian

infinia · 27th April 2006, 11:59 PM

Hi
Your link is broken?
Didn't find amp schematic.

substrate · 28th April 2006, 12:34 AM

doh! sorry about that. The link I originally posted was for another thread I was working on at the same time.

I could not find the original schematic I was referring to but I found the same arrangement in the following schematic (look at the bottom-center of the image):

http://www.guitar-parts.com/images/reverb6g15.JPG

Are they zeners?

-Brian

infinia · 28th April 2006, 01:02 AM

Series Si diodes to increase PIV (peak inverse voltage) of total string. Probably 1N400x 1 amp diodes. Does that make sense?

substrate · 28th April 2006, 02:05 AM

Ahh yes that makes perfect sence. It didn't click in but yea it's pretty obvious now. Thanks bud!

edl · 28th April 2006, 08:14 AM

Hi,

As I see, the supply is 300V-DC, then in my opinion a lonely 1N4007 will do the job, instead of the three diodes.

Regards,

B Cullingford · 29th April 2006, 04:09 AM

... and a better job, since the voltage across each diode may not be the same, and if you're a little unlucky one diode shorts followed very shortly by the others. Much better to use one diode, I believe that one can use resistors across the diodes to equalise the drops, still better to use one diode if possible.

27th April 2006, 11:49 PM	#1
substrate diyAudio Member Join Date: May 2003 Location: Winnipeg, MB, Canada	Question about weird diode arrangment I have a question regarding the following schematic (for a Fender guitar amp): http://www.st-andrews.ac.uk/~jcgl/Sc...oax/page6.html If you look at the upper-left corner of the schematic you'll see two branches with three diodes in series. I was wondering what the purpose is of having these three diodes in series like that, and also why they have the markings on the diodes "-" then "+" instead of the other way around? With a typical diode, wouldn't you indicate the "+" on the anode (non-stripe) and "-" on the cathode (stripe)? Me thinks that it's to drop the voltage, but the voltage is so high that I don't imagine that you'd get significant drop across the diodes. Thanks for any input. -Brian

27th April 2006, 11:59 PM	#2
infinia diyAudio Member Join Date: May 2005 Location: Californication	Hi Your link is broken? Didn't find amp schematic. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

28th April 2006, 01:02 AM	#4
infinia diyAudio Member Join Date: May 2005 Location: Californication	Series Si diodes to increase PIV (peak inverse voltage) of total string. Probably 1N400x 1 amp diodes. Does that make sense? __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

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28th April 2006, 12:34 AM	#3
substrate diyAudio Member Join Date: May 2003 Location: Winnipeg, MB, Canada	doh! sorry about that. The link I originally posted was for another thread I was working on at the same time. I could not find the original schematic I was referring to but I found the same arrangement in the following schematic (look at the bottom-center of the image): http://www.guitar-parts.com/images/reverb6g15.JPG Are they zeners? -Brian

28th April 2006, 02:05 AM	#5
substrate diyAudio Member Join Date: May 2003 Location: Winnipeg, MB, Canada	Ahh yes that makes perfect sence. It didn't click in but yea it's pretty obvious now. Thanks bud!

28th April 2006, 08:14 AM	#6
edl diyAudio Member Join Date: Oct 2004	Hi, As I see, the supply is 300V-DC, then in my opinion a lonely 1N4007 will do the job, instead of the three diodes. Regards,

29th April 2006, 04:09 AM	#7
B Cullingford diyAudio Member Join Date: Mar 2005 Location: California	... and a better job, since the voltage across each diode may not be the same, and if you're a little unlucky one diode shorts followed very shortly by the others. Much better to use one diode, I believe that one can use resistors across the diodes to equalise the drops, still better to use one diode if possible.

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