[Icom] PS-125 Mods - zener diode

Thu, 13 Feb 2003 14:31:59 -0500

Ken:

The Black (-) wire from the fan goes to the collector of Q14 (2SC943)
via connector CN15.  The Red wire goes through a 15 ohm resistor to the
PS-125 + DC output, also via connector CN15.

The emitter of Q14 is connected to common*(ground reference).  You will
find Q14 close to connector CN15.  I recommend connecting a 6.8 Volt, 1
Watt Zener Diode across Q14 with the anode connected to the emitter
(common), and the cathode to the collector.

If you don't feel comfortable removing the PC board from the chassis,
then a simple way to accomplish the equivalent is to connect the cathode
of the Zener diode to the Fan's Black (-) wire (tap into this wire and
insulate the connection), and then connect the anode to PS-125 DC output
Negative line (again you can tap into the wire, or solder to its
connector terminal).

Asterisk (*) above is to point out that that the chassis is not common
(ground reference), so please do not connect the zener diode anode to
chassis for a common (ground) connection.

Note: There is no reason to change the Fan unless it is defective.

If the above instructions are not clear to you, please feel free to ask
questions.

Good luck

Ted Marston, WA2RPI, Rochester, NY
[email protected]

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Ken Kinyon - W7TS
Sent: Thursday, February 13, 2003 11:46 AM
To: [email protected]
Subject: RE: [Icom] PS-125 Mods - zener diode

Was this done leaving the original fan? Is it possible to get a picture
of
where to place the diode.  there is not schematic in the small manual
that
came with my PS-125.
73,
Ken W7TS

-------------------
Kenneth E.  Kinyon
34 Princeton Circle
Longmont, CO 80503-2106
Voice: (303) 684-0037
Fax:  (303) 776-5088
E-mail: [email protected]
	  [email protected]
	  [email protected]
ALPCA #8339
ARRL-LM
-------------------

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of kevin schuchmann
Sent: Sunday, February 09, 2003 12:04
To: [email protected]
Subject: Re: [Icom] PS-125 Mods

Hi Dave,
    another mod  which I like better  is putting a 6.8 1w zener across
Q14,
Q14 is the control transistor for the fan,
this way the fan runs all the time but at a low quiet level, then if
things
really  get hot Q14 conducts and the fan can still go to
full speed...

btw this idea was wa2rpi's,   and has worked well here for about a
year...

73's
Kevin
wa6fwf

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