Steve, thanks for the heads-up re the TS-590 mod. I purchased mine new last
November; so, evidently, if I operate my ALS-600 with it, I really should
have the mod installed.

Ron, K8HSY
 


-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Steve Forst
Sent: Wednesday, July 02, 2014 1:10 PM
To: [log in to unmask]
Subject: Kenwood TS-590 ALC mod

Not sure if anyone else on the list 	has had this done, but figured I 
would share my experience.

First, don't take anything I say as Gospel, confirm with another source.

The 590 has had a known issue of ALC/power spike and Kenwood is now 
offering a free mod to fix.   You need to send the radio to a Kenwood 
service center at your expense, and Kenwood covers the mod and return
shipping.

If this spike exists on a particular radio, it could cause a solid state amp
(or some high end tube amps) to trip their protection circuit. 
Many solid state amp owners  have reported no problems and all works 
well.   others, like me, found the amp tripped with only modest drive.

in my case my THP 1.2kfx which  should put out 750 watts pep, with a 
drive between 75-90 watts, would trip off with  much less.   On 10 
meters I was limited to about 35 watts drive, 40 watts on 15, and 50 or 
so on 20 meters.   Lower bands could handle 60 watts.    More drive and 
the amp would trip.

Sent mine  out in  June to the Virginia Beach service center and had it 
back in 12 days.   Have had it back for a week and have run it with the 
ss amp and no problems.    Played some in the Canada Day contest on both 
15 and 20 meters running 70 watts drive and no problems.   THP is out of 
business now and this amp would be expensive to repair, so I will probably
limit drive to 65-70 watts and  hopefully the extra headroom will give it a
longer life. I'll treat it like a 550 - 600 watt amp instead of 750.

So I was happy with the result.   Your mileage may vary.  The mod 
consists of some hardware changes and some changes in the alignment 
procedure.   If your 590 was built starting in January 2014, the changes 
were implemented at the factory.   Anything built from 2010 - 2013  can 
get the mod if you desire.    Obviously most of these radios are long 
out of warranty, but kenwood is  treating this as a warranty repair. 
Mine was built in April 2011 and purchased in June 2011.

Anyway, that's my long winded story.

73, Steve KW3A