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Unfinished fisher 500 b

coman61

coman61

Well-Known Member
:boring: :boring: I still have not finised the Fisher 500 B. I'm stuck on these Diodes.
http://oldtech.net/Fisher/500B/schem1.gif. Please see CR 3 and cr4 in the schmatic. I keep reading about Fast recovery and soft recovery diodes Blah blah blah. OK so here is my question, what part number can be used here. I have seen these part numbers listed on the internet sites (RPG 300) (1n4531). Are these what I'm looking for? They are described as computer diodes. Power supply I assume??
Also Is c14 and c15 the caps for phono upgade in this schmatic?http://oldtech.net/Fisher/500B/schem2.gif.. and for now one more question. Where are the tone control Caps? Thanks in advance. Coman61
 
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go to Digi-Key and put "Fast Recovery" as the search term. It will return a potload of choices. Then pick the ones that meet your voltage/current requirements. I think I got 600v 3amp diodes for my Fisher 400.
 
MUR4100 will sub for most any diode you'll ever need - 4A, 1000V, fast recovery, 56 cents each at DigiKey.com. FR-307 is similar (3A), same price.

FR307 is 41 cents at Mouser.com, or the UF5408 for 32 cents each.

Dunno about the phono, but the tone control caps are the ones connected to filter and loudness switches, and bass/treble controls.
 
Hey-Hey!!!,
I'll second the UF5408. They're quite tough, and also useful for DC filament supplies. When used with L-C filters, they stand a large start-up spike that can cause trouble for lesser diodes. Get a belt of them, they're useful.

Considering what they'd be replacing a 1N4007 will live there comfortably...
cheers,
Douglas
 
Hey-Hey!!!,
The SiC Zero-Recovery from Cree are the ne plus ultra of the SS diode world.

http://www.cree.com/products/power.htm

I have used them, and they are quite good. Tube Builder in Maryland used to sell 600V/1A for $1. I got some of the 1k2V/5A ones, and I will *NOT* be doing without...even at a few dollars a piece...if you need the best, there is no substitute.

There are some 1kV/1A in Mouser IIRC. Should make a reasonable substitute if yo can't get the Cree's.
cheers,
Douglas
 
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