Good sources for high-V (600V) Schottky diodes?

GordonW · 20th March 2007, 07:47 PM

Looking to upgrade the B+ rectifiers on my old HK Award A300 tube amp.

It'd need two 600v Schottky diodes, to do it right. 1 amp should be PLENTY, I'd think.

However, I've only found limited availability of these... nothing that was JUST right. Anyone got any good sources for these things? Basically, a standard "axial" configuration (ie, one wire out each end) would be best...

Regards,
Gordon.

Duo · 20th March 2007, 07:48 PM

Why does this amplifier require schottky diodes?

GordonW · 21st March 2007, 02:53 PM

More graceful on-off characteristics than regular junction diodes... less switching noise. The characteristics of a Schottky more resemble that of a tube rectifier, but with much less voltage drop.

The HK originally had solid-state diodes... which had bypass caps on them, to try and snub the switching noise. With the Schottkys, there should be almost no noise TO have to bypass/filter...

Regards,
Gordon.

resident · 21st March 2007, 03:09 PM

search for the HFA08TB60

they're not axial though............ but too fast

serengetiplains · 23rd March 2007, 03:41 PM

Parts Connexion sells them.

GordonW · 24th March 2007, 06:13 PM

Found them. Cree 600v, 2A. From Digikey. Less than $2 each!

They also have 1200V; in this case, I only needed 400V minimum, so the 600V were perfect...

Regards,
Gordon.

serengetiplains · 24th March 2007, 07:11 PM

Nice find, Gordon. Say, can these devices be paralleled, without more, for greater current handling?

MatchASM · 24th March 2007, 11:55 PM

Quote:

Originally posted by serengetiplains
Nice find, Gordon. Say, can these devices be paralleled, without more, for greater current handling?

I would recommend against that, because if the junction voltage drops aren't exactly equal, the current distribution will be highly asymmetrical and thus you will not benefit from the parallel connection.

On the other hand, Schottkies have a lower voltage drop than regular diodes, so I would not expect them to heat up very significantly. Has anyone ever tried running these things "over spec"?

jcx · 25th March 2007, 03:47 AM

parallel with balancing resistors

semi diodes are going to be way lower impedance than any tube they replace

and don't count on exceeding power device ratings - the marketing guys would dearly love to put bigger # on the data sheet, they often get sneaky by specifying unrealistically optimistic heatsinking as is - cautious engineers often derate device operating conditions to <50% of the data sheet value

20th March 2007, 07:47 PM	#1
GordonW diyAudio Member Join Date: Mar 2005 Location: Marietta/Moultrie GA	Good sources for high-V (600V) Schottky diodes? Looking to upgrade the B+ rectifiers on my old HK Award A300 tube amp. It'd need two 600v Schottky diodes, to do it right. 1 amp should be PLENTY, I'd think. However, I've only found limited availability of these... nothing that was JUST right. Anyone got any good sources for these things? Basically, a standard "axial" configuration (ie, one wire out each end) would be best... Regards, Gordon. __________________ Speaker Design, Restoration and Repair- since 1985.

21st March 2007, 02:53 PM	#3
GordonW diyAudio Member Join Date: Mar 2005 Location: Marietta/Moultrie GA	More graceful on-off characteristics than regular junction diodes... less switching noise. The characteristics of a Schottky more resemble that of a tube rectifier, but with much less voltage drop. The HK originally had solid-state diodes... which had bypass caps on them, to try and snub the switching noise. With the Schottkys, there should be almost no noise TO have to bypass/filter... Regards, Gordon. __________________ Speaker Design, Restoration and Repair- since 1985.

23rd March 2007, 03:41 PM	#5
serengetiplains diyAudio Member Join Date: Feb 2004 Location: Canada	Parts Connexion sells them. __________________ Tom

24th March 2007, 06:13 PM	#6
GordonW diyAudio Member Join Date: Mar 2005 Location: Marietta/Moultrie GA	Found them. Cree 600v, 2A. From Digikey. Less than $2 each! They also have 1200V; in this case, I only needed 400V minimum, so the 600V were perfect... Regards, Gordon. __________________ Speaker Design, Restoration and Repair- since 1985.

24th March 2007, 07:11 PM	#7
serengetiplains diyAudio Member Join Date: Feb 2004 Location: Canada	Nice find, Gordon. Say, can these devices be paralleled, without more, for greater current handling? __________________ Tom


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20th March 2007, 07:48 PM	#2
Duo diyAudio Member Join Date: Jun 2002 Location: Victoria, BC, Canada	Why does this amplifier require schottky diodes?

21st March 2007, 03:09 PM	#4
resident Account Disabled Join Date: Sep 2004 Location: Earth	search for the HFA08TB60 they're not axial though............ but too fast

25th March 2007, 03:47 AM	#9
jcx diyAudio Member Join Date: Feb 2003 Location: ..	parallel with balancing resistors semi diodes are going to be way lower impedance than any tube they replace and don't count on exceeding power device ratings - the marketing guys would dearly love to put bigger # on the data sheet, they often get sneaky by specifying unrealistically optimistic heatsinking as is - cautious engineers often derate device operating conditions to <50% of the data sheet value

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