[Kenwood] The 'problem' is probably faulty research

[Garey Barrell]

There are several "weak points" in the TS-940 power supply.

1.  The pass transistors in the +24V regulator circuit are marginal.  
Experienced repair people recommend replacing the original 2N5885 (60V) 
devices with 2N5886 (80V).    Bad news here is if they DO fail, they 
take out the driver transistors and often the finals as well when the 
+24 goes to +40.

2.  The AVR board, (small board on top,) has several undersized PC board 
traces, which combined with several VERY hot running devices leads to 
lifted traces.  Lot's of connectors, several with large pins with no 
support, leading to cracked solder joints.  Several Zener diodes that 
are marginal at 400 mW ratings, and should be replaced with 1W devices.  
Most all the electrolytic capacitors are past their expected life, 
exacerbated by the high heat levels in the area.

3.  The PS fan is also probably near the end of it's life.  This fan 
runs most of the time the rig is on, even in receive only operation.  
And when it quits, the heat really goes up, finishing off the AVR board!

73, Garey - K4OAH
Atlanta

Drake B & C-Line Service CDs
<http://www.k4oah.com>



Brian wrote:

>A "history of power supply problems" ???  Please, expound on this for us, if
>you would.
>
>I tried searching Google for  "Kenwood TS-940 power supply problem" which
>only returned 250 results -- none of which actually linked to a page
>detailing, outlining, or otherwise mentioning a problem with the TS-940
>...and a few that mentioned having a power supply problem with <insert rig
>here>, and thus deciding to buy a TS-940 to replace their problematic rig.
>
>As a TS-940 owner, I would truly like to hear about these potential power
>supply flaws...  Until now, I hadn't heard of them (nor had my 15+ year old
>TS-940, which is still working [every day] like the day it was brand new).
>
> 73 de AI4AI,
> - Brian
>
>
>-----Original Message-----
>From: kenwood-bounces at mailman.qth.net
>[mailto:kenwood-bounces at mailman.qth.net] On Behalf Of Joe Eide
>Sent: Monday, March 20, 2006 7:53 AM
>To: kenwood at mailman.qth.net
>Subject: [Kenwood] Re: Kenwood Digest, Vol 23, Issue 16
>
>Ted
>
> From a distance, I would suspect power supply problems.  The 940 has a
>history of power supply problems and that would affect several areas of
>operation.
>
>Joe - KB9R
>  
>