[ARC5] Paralleling Rectifier Diodes

[Dennis Monticelli]

At the 10A level the ESR of the diode exceeds any variation in diode
threshold so matching is not necessary.  You should replace both diodes.
Diodes are inexpensive.   You could parallel up some common axial 3A diodes
vs looking for a 10A stud type.

As a test you could even stack up cheap-as-resistors 1A diodes (that you
may already have in your junk box) to see if indeed diodes are the problem.

Dennis AE6C

On Sun, May 5, 2024 at 11:30 AM Ken <kgordon2006 at frontier.com> wrote:

> Although I have never yet had an occasion to do this, my understanding of
> the process of paralleling diodes, especially solid-state ones, is that one
> must include a low-value resistor, appropriately sized for power, in series
> with each.
>
> Even so, doing this is not recommended by anyone I remember reading from
> over the years.
>
> And, of course, adding resistance in the circuit adversely effects
> regulation.
>
> Ken W7EKB
>
>
>
> Sent via the Samsung Galaxy S21 5G, an AT&T 5G smartphone
>
>
> -------- Original message --------
> From: releazer at earthlink.net
> Date: 5/5/24 11:19 (GMT-08:00)
> To: arc5 at mailman.qth.net
> Subject: [ARC5] Paralleling Rectifier Diodes
>
> Yesterday I found a 12/24V 10 amp battery charger someone tossed out.  It
> seems to work fine on the 12V setting but the voltage output is only 22V on
> the 24V setting even with no load.  Oddly enough it uses a center tapped
> transformer and two rectifier diodes to produce a full wave output,
> although without any filter caps.  It seems that one of the rectifier
> diodes has an excessive voltage drop on the 24V setting.  How would you
> parallel rectifier diodes, in case I do not have any suitable diodes to
> replace the defective one?
>
> Thanks
>
> Wayne
> WB5WSV
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