Diodes to protect OT's..

JandG · 29th April 2009, 01:24 PM

Can someone show on a schematic how to wire diodes up for SE & PP amps for OT protection, & what value & type of diodes should be used..?
Thanks Joe

Bandersnatch · 29th April 2009, 01:43 PM

What are you protecting it from?
cheers,
Douglas

mashaffer · 30th April 2009, 01:00 AM

Are you thinking of diodes to clamp the secondary voltage if operated into an open circuit?

Geek · 30th April 2009, 01:06 AM

Common as dirt on guitar amps.

Most are wired diode cathode to plate, diode anode to ground. One diode for SE, one on each side for PP.

Use a fast recovery type rated at LEAST twice the supply voltage and preferably four times. 3A is a good current (larger diode area is more forgiving).

Cheers!

Wavebourn · 30th April 2009, 01:36 AM

For SE a diode can't help. Rather a bridge with powerful Zener in secondary.

Geek · 30th April 2009, 02:14 AM

Quote:

Originally posted by Wavebourn
For SE a diode can't help. Rather a bridge with powerful Zener in secondary.

Dummy me for not catching that one

He's right... it'll cutoff part of your waveform.

Cheers!

JandG · 30th April 2009, 02:47 AM

Sorry for slow responce.
I am wanting to protect my OT's from whatever happens when a output tube goes bad, runaway, blowup, melts internaly, etc..Rectifier going to the bad, me hitting something I should not when probing hot, etc. If I could see a schematic for decent protection for voltage spikes , shorting , to much current, etc. for PP amps, & SE amps, with eather fixed or cathode bias. I would implement them in all my amps. I do have bad luck with output tubes & allways feel lucky when the OT's still work after words. I have read that fuses are not the answer & can be actually worse. I do not know as I am not at the level of knowing if true or not. I just can't imagine everyone with rarer than heck vintage OT or spendy new iron, not protecting them. I never see circuits implementing such protection. Maybe it is all for not & nothing to be conserned about..?
Joe

Geek · 30th April 2009, 05:41 AM

Oh... you don't want a rectifier, you want a cathode fuse

Wavebourn · 30th April 2009, 05:54 AM

...or a microcontroller with sensors of everything out of regime...

29th April 2009, 01:24 PM	#1
JandG diyAudio Member Join Date: Jan 2005 Location: Washington State	Diodes to protest OT's.. Can someone show on a schematic how to wire diodes up for SE & PP amps for OT protection, & what value & type of diodes should be used..? Thanks Joe

29th April 2009, 01:43 PM	#2
Bandersnatch diyAudio Member Join Date: Jul 2003 Location: Ann Arbor, MI	What are you protecting it from? cheers, Douglas __________________ the Tnuctipun will return

30th April 2009, 01:00 AM	#3
mashaffer diyAudio Member Join Date: Jun 2004 Location: Indiana	Are you thinking of diodes to clamp the secondary voltage if operated into an open circuit? __________________ mike - www.keepingsundayspecial.org

30th April 2009, 01:36 AM	#5
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	For SE a diode can't help. Rather a bridge with powerful Zener in secondary. __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

30th April 2009, 05:54 AM	#9
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	...or a microcontroller with sensors of everything out of regime... __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

30th April 2009, 01:06 AM	#4
Geek diyAudio Member Join Date: Sep 2004	Common as dirt on guitar amps. Most are wired diode cathode to plate, diode anode to ground. One diode for SE, one on each side for PP. Use a fast recovery type rated at LEAST twice the supply voltage and preferably four times. 3A is a good current (larger diode area is more forgiving). Cheers!

30th April 2009, 02:47 AM	#7
JandG diyAudio Member Join Date: Jan 2005 Location: Washington State	Sorry for slow responce. I am wanting to protect my OT's from whatever happens when a output tube goes bad, runaway, blowup, melts internaly, etc..Rectifier going to the bad, me hitting something I should not when probing hot, etc. If I could see a schematic for decent protection for voltage spikes , shorting , to much current, etc. for PP amps, & SE amps, with eather fixed or cathode bias. I would implement them in all my amps. I do have bad luck with output tubes & allways feel lucky when the OT's still work after words. I have read that fuses are not the answer & can be actually worse. I do not know as I am not at the level of knowing if true or not. I just can't imagine everyone with rarer than heck vintage OT or spendy new iron, not protecting them. I never see circuits implementing such protection. Maybe it is all for not & nothing to be conserned about..? Joe

30th April 2009, 05:41 AM	#8
Geek diyAudio Member Join Date: Sep 2004	Oh... you don't want a rectifier, you want a cathode fuse

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