[Amps] SB-200 power supply diodes

[Paul Kraemer]

Excellent point Gerald
I also  wonder if any one has done the math or actually measured the 
increase in diode / transformer current from arbitrarily increasing the 
original filter cap size from the original 125 mfd to say 330 mfd in those 
doubler supplies. I realize those original caps were probably 10 pct or more 
over the labled value and the new one will likely be 10 pct under. Still, it 
is a change and it does matter.
Someday I'm gonna take the HP 428 and actually measure before and after 
transformer current, just out of curiousity.
Paul K0UYA
----- Original Message ----- 
From: <TexasRF at aol.com>
To: <w7ry at inbox.com>; <4cx250b at muohio.edu>; <amps at contesting.com>
Sent: Sunday, March 27, 2011 8:00 AM
Subject: Re: [Amps] SB-200 power supply diodes


> Think about this again. The SB200/220 both use a voltage doubler capacitor
> filter hv supply. We know that peak currents in these type supplies can be
> five  to ten times the average current.
>
> So, with a .6 to .7 ampere average, those diodes are taking a 3 to 6 
> Ampere
> hit 60 times every second.
>
> For the miniscule added cost it makes a lot of sense to use 1N5408 diodes.
> Reaming the mounting holes for the larger lead size is a trivial  effort.
>
> If 1N5408 diodes had been available when those amplifiers were  designed 
> no
> doubt they would have been used. Especially so when you consider the
> equalizing capacitors and resistors would not be needed. I would remove 
> them now
> as the parts that are not there can't fail. Who knows what those resistor
> values  might be after upwards of 50 years use?
>
> 73,
> Gerald K5GW