"dimple" diodes are the German version of ......... YES, it's a
"simple" diode.
I build and sell PC's professionally. I often use diode strings
to control fan speeds (and noise level) of the computers.
I've used it for linears' fans for about 25 years now too. As
you pointed out, it works great for designing cheap and easy
adjustable bias for multi-tube linears (like the old sweep tube
linears). Can't imagine using a resistor instead.
Flexibility: Put in a large diode string and then a small switch
(toggle or multi-pole) to switch taps on the diode string. For
normal use, run the fan low - for contest, flip a switch and the
fan speeds up to compensate for the continuous duty operation.
Easy as die (I mean pie).
By the way Pat, don't you use tiepo's to attach the antenna to
the mast? ;-)
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Patrick A.
Thompson
Sr.
Sent: Sunday, January 18, 2004 11:18 PM
To: Rick@dj0ip.de; tentec@contesting.com
Subject: RE: [TenTec] Centaur quiet fan?
I guess the "dimple" diodes are the really cute ones? sorry ;-)
I meself hav never ade a tiepo!
Using the forward voltage drop across a diode is a great way to
drop a small
voltage. The drop will be reasonably constant with varying
current and that
can be a plus. I've used similar circuits to drop voltage to HT's
from 12vdc
supplies and I've seen a string of diodes used to provide
variable bias for
a tube amp, or raise the ground pin of a 7812 regulator to bump
the voltage
up. If you had to buy a suitable resistor instead of already
having a junk
box item the diodes would probably be cheaper.
Pat
wa4tuk
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Rick Westerman
Sent: Sunday, January 18, 2004 1:19 PM
To: tentec@contesting.com
Subject: RE: [TenTec] Centaur quiet fan?
The best and easiest way to reduce fan noise is to place several
dimple diodes in the 13.8v line going to the 12v fan.
Use diodes such as 1N4007 (or anything similar). You get about
0.6 to 0.7 volt drop for each diode in the string. Just a couple
of volts less to the fan reduces noise noticably.
73
Rick
(Assuming it's a 12 v fan of course - I can'y remember and I
don't have my Centaur anymore)
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of John Rader
Sent: Sunday, January 18, 2004 7:04 PM
To: tentec@contesting.com
Subject: RE: [TenTec] Centaur quiet fan?
Well,
I went shopping for a new fan at several of the D/FW electronic
stores. I found a number of AC fans that are direct replacements.
Some had lower Db and similar CFM specs but, none were quieter.
So I put in a 150 ohm 25 watt resistor.
John K5XTX
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