From: saltzman@ISOVAX (Bob Saltzman)
Newsgroups: rec.radio.amateur.misc
Subject: Kenwood TS-520 help needed
Date: 15 Oct 92 13:06:47 GMT
Reply-To: saltzman@ISOVAX
Organization: GE Corporate Research & Development, Schenectady, NY

I have a Kenwood TS-520 and TS-520S HF transceiver, both in excellent 
condition.  As I compared the performance of the receivers against each 
other last week I observed some significant differences that caused me 
to look into tuned circuit alignment.  As expected, the poorer performer 
was quite out of alignment.  I have the operator and service manuals, 
and following the recommended procedures was able to significantly 
improve the alignment of the weaker system (TS-520S) on all bands - 
until I got to the 28Mhz band.  

As I attempted to very carefully turn the ferrite tuning slugs in the 
28Mhz variable inductors, I found them immovable and the hexagonal keys 
behaving like they were 'stripped' (As a former TV/electronics 
repairperson, I was using a professional tuning tool - I do not have the 
ones that were originally shipped with the transceiver).  Other than 
some initial movement, about a 1/4 turn, I am unable to turn these slugs
in either direction.  It appears that the slugs, of soft composition, 
are in fact damaged.

Interestingly this problem only exhibits itself with the 28Mhz coils, 
antenna, oscillator, mixer and driver - all of the coils in the other 
bands could be easily manipulated and appear to be made of harder 
ferrite composition.  I noticed that the tops of each of the 28Mhz slugs
appear to have a pink-red color code painted on them, leading me more to
believe that they are of different ferrite composition than the others.  
None of the other slugs have any color coding.

The problem of course is what to do to replace these slugs and/or coils 
in order to align this transceiver band.  I called the Kenwood east 
coast parts distributor and as expected they told me that the parts (I 
have part numbers from the service manual) are no longer available.  
They recommended that I call the factory.  I talked to Kenwood customer 
service, and they told me the same thing.  I insisted that they bring 
this matter to the attention of the engineering department which they 
agreed to do.  My contention was that the TS-520 is still a widely used 
transceiver and parts replacement and/or substitution is an important 
issue for the owners of this almost 20 year old unit.  

I got a call back from Kenwood with a discouraging response.  The 
engineers agreed with my concerns and in fact have been trying for quite 
some time to get coil replacement information from Kenwood Japan, but 
unsuccessfully.  They had no other information to give me and in effect 
said, sorry, you're out of luck - clearly and unsatisfactory response.  

There is no doubt in my mind that other TS-520 owners have encountered 
this type of problem (with these specific coils, or with other parts) 
and maybe they have shared their problem with other Network News or 
Kenwood users group users.  

Does anyone have any recommendations or specific information on how I 
might repair or replace these defective coil/coil-slugs in my
transceiver?  I have a junk box full of all sorts of slug-tuned coils, 
some of which may physically fit in the TS-520 forms, but I would not
assume that ferrite characteristics are irrelevant.  I also do not want 
to destroy the existing slugs until I have a course of action with a 
predictable outcome (I am not certain how far out of alignment the 28Mhz 
tuned circuits are).  

I have communicated with ARRL Lab on this matter via email.  They have 
suggested trying to connect with a Kenwood users group for help.  Anyone 
aware of such a group?  They also referred me to replacement coil 
manufacturer Toko, a good idea if I had the electrical specs of the 
coils.  Another suggestion was to acquire a 'scrap' TS-520 for parts, 
but that seems to be an unlikely opportunity.  I have never seen a 
junker.  I bought both my rigs in excellent condition for the going 
price, and plan to sell the TS-520 as soon as I get the TS-520S problem 
resolved.  I can't see scavenging a perfectly good rig for parts yet.  

Any help that anyone can give me with this, or other TS-520 problems, 
would be greatly appreciated.  I have been told that this matter has 
been discussed in Network News before, but as it is new to me, and I a 
relatively new net news user, I was not aware of it.  

Thanks in advance for any help.

Bob Saltzman, WB2ARK            saltzman@crd.ge.com
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