I'm looking to resuscitate my old Aragon 4004MkII, which had developed a substantial hum some years back. The existing rectifiers are KBPC3504DW units, and while the diodes still look superficially functional, the reverse current is wildly out of spec on several of them (according to my $15 ebay part checker), and when hooking them up to my bench supply and testing with higher voltage, they reverse conduct >100ma at less than 5 volts.
Sourcing replacements is easy enough (though I'm not sure what the "D" in the part number stood for,) but I'm thinking perhaps something better might be available, considering the years elapsed. I've read a few discussions on the topic, but it's far enough out of my expertise that I can't really assess who knows what they're talking about.
So any suggestions for something that's not too much more expensive than the replacement rectifiers (less than double the $4.20 each for original)? Or perhaps there's some established design for a similarly powerful amp that I could crib off of. I have no issues with soldering together discrete diodes to build them up.
For reference, the supply is +/- 70V, 18000uf capacitors, and the transformer windings measure .5 ohm. I'm not sure how to calculate the startup surge, but I'd have to guess 'substantial."
Sourcing replacements is easy enough (though I'm not sure what the "D" in the part number stood for,) but I'm thinking perhaps something better might be available, considering the years elapsed. I've read a few discussions on the topic, but it's far enough out of my expertise that I can't really assess who knows what they're talking about.
So any suggestions for something that's not too much more expensive than the replacement rectifiers (less than double the $4.20 each for original)? Or perhaps there's some established design for a similarly powerful amp that I could crib off of. I have no issues with soldering together discrete diodes to build them up.
For reference, the supply is +/- 70V, 18000uf capacitors, and the transformer windings measure .5 ohm. I'm not sure how to calculate the startup surge, but I'd have to guess 'substantial."
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Quasimode snub whatever you buy
You can look the thread up, but if you don’t have a scope or can’t borrow one just forget it.
You can look the thread up, but if you don’t have a scope or can’t borrow one just forget it.
That is a pic of a 4004.
I'm wondering of something like this would be appropriate and reduce the need for a snubber?
https://www.mouser.com/datasheet/2/308/MBR40250_D-1810961.pdf
I'm wondering of something like this would be appropriate and reduce the need for a snubber?
https://www.mouser.com/datasheet/2/308/MBR40250_D-1810961.pdf
If using Schottky's for high voltage use decent heat-sinking. At high voltage the massive reverse leakage of Schottky's can cause catastrophic thermal run-away - reverse leakage increases exponentially with temperature to 10mA or more, leading to more heating, vicious circle. Don't just base their thermal performance on forward current...
