Diodes On Rectifier Question

Trout · 9th April 2008, 09:35 PM

I was just looking over the service manual diagram for the Re-issue 1957 5E3 Deluxe and saw something I do not recall ever seeing before.

A pair of avalanche rectifier diodes inline with the 5Y3 rectifier tube?

BYD33V data sheet

What would be the purpose of these diodes in this location?

Trout

Psychobiker · 9th April 2008, 10:16 PM

Back EMF protection? Bizarre though, as the 5Y3 itself is a diode, but perhaps a pre-emptive strike in case of arcing from a cap further down the line (unlikely or what!! But flashover at >300V can't be nice at any time) and not to fry the trafo?

Trout · 9th April 2008, 10:54 PM

I found it odd, because the 1950's units of course did not have these, and many are still functioning perfectly after 50+ years.

I have built a few 5E3 amps from kits and from scratch and the only thing I see different is the diodes in the new units.

another noteworthy item would be the original units did not have a standby switch.
On all of the ones I built it is common to get a POP when flipping the standby switch.

On the Re-Issue unit they interrupt the HV CT, I have tried that setup as well as interrupting the B+ lead on pin 8 of the 5Y3, both techniques pop when entering standby unless you put a .05/630V cap across the switch.

Maybe they felt the diode was a cheaper way to protect the PT instead of a fuse?

Trout

tubelab.com · 10th April 2008, 02:24 AM

Quote:

On the Re-Issue unit they interrupt the HV CT

You have found the reason for the avalanche rated diodes. Some users had FRED diodes short out when flipping the standby switch on the SimpleSE amplifiers. One user had a 5AR4 self destruct. Some glitch capturing with a storage scope revealed some serious transients generated form the collapsing magnetic field in the power transformer. It is transformer dependent, and spikes of over 3KV have been seen on some Hammond transformers. The avalanche rated diodes allow most of the transient to be dissipated before becoming a lightning bolt inside the 5Y3.

Trout · 10th April 2008, 03:31 AM

Sweeet, this might actually be useful information.

I have on several occasions seen arcs in the rectifer tubes on these old amps after adding standby switches. I'll have to order a few and try it out.

Thanks for the scoop.

Trout

Trout · 10th April 2008, 04:10 AM

Hmmmm,
anyone have a possible source for these diodes? I am not seeing them at my usual sources like Mouser, or Allied.

Trout

Psychobiker · 10th April 2008, 07:02 AM

radionics or farnell?

tubelab.com · 10th April 2008, 07:31 PM

Quote:

anyone have a possible source for these diodes? I am not seeing them at my usual sources like Mouser, or Allied.

Can't find those, but here are some other diodes with similar characteristics. I have not tested them yet.

Fairchild ISL9R8120P2 (got some from a SMPS project)
BYT52
BY228
1N5062
IXYS DSA2-1600 (too expensive)

Tom Bavis · 10th April 2008, 07:58 PM

Add MUR4100E to that list _ I think Mouser may have those. 'E' suffix is avalanche rated for ONSemi (formerly Motorola Semiconductor).

luvdunhill · 10th April 2008, 11:16 PM

BYV96E is a very nice diode that I use a lot... Ebay is the best place I know to find it.

Datasheet:

http://www.ortodoxism.ro/datasheets/eic/BYV95C.pdf

Ebay:

http://cgi.ebay.com/Recitifier-Silic...2em118Q2el1247

(if this is totally not what you're talking about, I apologize in advance)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
FS: Lot of IR rectifier diodes	luvdunhill	Swap Meet	1	4th February 2009 02:19 PM
Rectifier diodes for UcD 400	m.parigi	Class D	6	14th March 2005 09:42 AM
Integrated Rectifier Bridge VS Rectifier Diodes	Sci	Chip Amps	11	16th July 2004 02:43 PM
Rectifier Diodes	richie00boy	Parts	6	19th April 2004 01:41 PM
GaAs rectifier diodes	ergo	Parts	1	13th August 2003 04:45 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

9th April 2008, 10:16 PM	#2
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Montréal QC	Back EMF protection? Bizarre though, as the 5Y3 itself is a diode, but perhaps a pre-emptive strike in case of arcing from a cap further down the line (unlikely or what!! But flashover at >300V can't be nice at any time) and not to fry the trafo?

9th April 2008, 10:54 PM	#3
Trout diyAudio Member Join Date: Nov 2004 Location: Midwest Madman	I found it odd, because the 1950's units of course did not have these, and many are still functioning perfectly after 50+ years. I have built a few 5E3 amps from kits and from scratch and the only thing I see different is the diodes in the new units. another noteworthy item would be the original units did not have a standby switch. On all of the ones I built it is common to get a POP when flipping the standby switch. On the Re-Issue unit they interrupt the HV CT, I have tried that setup as well as interrupting the B+ lead on pin 8 of the 5Y3, both techniques pop when entering standby unless you put a .05/630V cap across the switch. Maybe they felt the diode was a cheaper way to protect the PT instead of a fuse? Trout

10th April 2008, 03:31 AM	#5
Trout diyAudio Member Join Date: Nov 2004 Location: Midwest Madman	Sweeet, this might actually be useful information. I have on several occasions seen arcs in the rectifer tubes on these old amps after adding standby switches. I'll have to order a few and try it out. Thanks for the scoop. Trout

10th April 2008, 04:10 AM	#6
Trout diyAudio Member Join Date: Nov 2004 Location: Midwest Madman	Hmmmm, anyone have a possible source for these diodes? I am not seeing them at my usual sources like Mouser, or Allied. Trout

10th April 2008, 07:02 AM	#7
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Montréal QC	radionics or farnell?

10th April 2008, 07:58 PM	#9
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	Add MUR4100E to that list _ I think Mouser may have those. 'E' suffix is avalanche rated for ONSemi (formerly Motorola Semiconductor).

10th April 2008, 11:16 PM	#10
luvdunhill diyAudio Member Join Date: Jul 2006	BYV96E is a very nice diode that I use a lot... Ebay is the best place I know to find it. Datasheet: http://www.ortodoxism.ro/datasheets/eic/BYV95C.pdf Ebay: http://cgi.ebay.com/Recitifier-Silic...2em118Q2el1247 (if this is totally not what you're talking about, I apologize in advance)

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)