[Kenwood] Kenwood TS-940SAT S Meter

Thu Feb 19 16:01:39 EST 2015

Hi,this evening I replaced the two attenuator relays that are in the RF unit with two OMRON units as suggested by Clif, and the problem was completely gone! As new life for my TS-940. (So I decided to replace also the third relay, RL3, of the same type. )
It was not necessary to replace the TX/RX reed relay.Thanks to Clif for the precious suggestions.73MarioIZ0IRH (KK6GYP)

      Da: Clif <clif at avvid.com>
 A: Brian Tempero <btempero at stanford.edu> 
Cc: MarioDaniele Greco <daniele_mdg at yahoo.it>; "kenwood at mailman.qth.net" <kenwood at mailman.qth.net> 
 Inviato: Giovedì 5 Febbraio 2015 16:28
 Oggetto: Re: [Kenwood] Kenwood TS-940SAT S Meter

It's labeled RB and in the first set of instructions for alignment.

Might I suggest you not adjust anything, it's working. A lot of the adjustments require test equipment beyond most home shops. Some of the adjustments seem benign enough like the AGC voltage setting. But when you adjust the AGC voltage you have to recalibrate the S-Meter. The service manual expects you to start on Pg 1 and go thru every step in order. A lot of steps affect steps on down the page so you can't jump around. If you want to go thru and take notes on the different readings in each step without adjusting anything that's OK.

First Rule: "If it ain't broke, don't fix it"

On Wed, Feb 4, 2015 at 10:50 PM, Brian Tempero <btempero at stanford.edu> wrote:

Clif,
Thank you for the information. I did the “internal Calibrator” test per your instructions and it read S9. May I ask another question? On page 50 of the users guide. Section 11-2 adjustments 1 and 2. Where do I put the leads of my volt meter to test the voltage? I looked in the service manual and it was still vague. 
Thank you very much for your help. I really appreciate it. 
Brian TemperoHIVE Manager650-724-8122

From:  Clif <clif at avvid.com>
Date:  Wednesday, February 4, 2015 at 9:27 AM
To:  MarioDaniele Greco <daniele_mdg at yahoo.it>
Cc:  ICME <btempero at stanford.edu>, "kenwood at mailman.qth.net" <kenwood at mailman.qth.net>
Subject:  Re: [Kenwood] Kenwood TS-940SAT S Meter

Easiest way to check is turn on the internal calibrator. It is after the attenuator relays and leaves them out as a problem. It should read S7-9 on a properly aligned radio on 20m @ 14.2 in USB. If that is correct and an on air signal is way low then the attenuator relays need to be replaced. If it's not S-7-9 a signal calibrated output generator is needed to determine if the problem is s-meter setting or the rx sensitivity is actually down due to a problem.

As a note the 940's were aligned to the Collins spec, 50uv = S-9, FWIW S-1 = 1.25uv. The levels in the service manual are different because the SG output is speced into an open load not 50 ohm.

On Wed, Feb 4, 2015 at 11:06 AM, MarioDaniele Greco <daniele_mdg at yahoo.it> wrote:

Hi,
same "problem" here with my TS-940, one of the latest serial numbers, 9 Millionxxx. My S-meter moves only when signals are stronger than S5-S6.Some typical TS-940  issues are :- S-meter scale is calibrated according to Japanese scale, where S1 japanese = S5 in the  Collins USA signal scale.- there is a PIN diode attenuator, in RF board,  exactly after the RX input filters, before the RF cascode FET amplifier,  that could be out of calibration: the reference value is adjusted by VR1 in RF board. See service manual for the right values
- the input attenuator relays could have dirty contacts
Last, but not least, if your radio is very old, it could be necessary to check the whole RF-IF signal chain. The Service Manual is of help.
Just try this : switch to lower band, 500KHz - 1.5 MHz: if  the received signals or noise level is strong, and the S-meter goes to S6 or beyond, this means that the at least the signal chain is OK, otherwise it needs to be services.Hope this helpes73MarioIZ0IRH
     Da: brian tempero <btempero at stanford.edu>
 A: kenwood at mailman.qth.net
 Inviato: Martedì 3 Febbraio 2015 18:19
 Oggetto: [Kenwood] Kenwood TS-940SAT S Meter

All,

This is my first post. I have a strange issue with my kenwood ts-940SAT.
Here is the issue:
My radio receives and transmits very well. The issue is that my S meter
barely works. If a really strong signal comes in the needle spikes and then
slowly descends. If the signal is not really strong the needle does not
move.
When I transmit the needle works without issue in all settings (power, swr,
acl and so on).  I have all the knobs set per the operating manual for first
use. I am stumped at this issue.

Thank you for reading this issue and all comments or suggestions are
welcome.

Brian Tempero
HIVE Manager
Stanford University
650-724-8122

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-- 
Clif Holland KA5IPF
www.avvid.com

-- 
Clif Holland KA5IPF
www.avvid.com