[Kenwood] TS-940 missing Resistor 152 on IF Board, anyone know why?

[Garey Barrell]

Perhaps I'm just too trusting, but I figure Kenwood knows more about 
what should or should not be on a particular board than any "field 
techs".   IF there is a location for a part, and there are burned pieces 
sticking up, leads cut off, or otherwise an indication that there WAS a 
part there when it came from the factory, then yes, I'm going to find 
out what should be there and replace it.  When there is no indication at 
all that a part was EVER installed there, I'm going to assume that it's 
NOT supposed to be there.  I've been working in this field long enough 
to know that there are "post-production" changes that sometimes call for 
removal of a part.  It might be due to a device change, circuit change 
or other perfectly valid reason.  Engineers aren't perfect, and 
circumstances DO change.  You may also find parts soldered on the "back" 
of a board for the same reason.  Sometimes it's because a vendor has 
made what to them was a "minor" change in a device, but it happens to be 
a "critical" change in your particular circuit.  Sometimes the 
variations in production show a trend that calls for a change, but not 
significant enough to warrant a redesign of a PC board.

Assuming you trust Kenwood enough to spend a couple thousand bucks on 
one of their products, I think you should trust that your unit passed 
final test, and meets published specs.  If you  aren't comfortable doing 
that, then perhaps you should buy another brand.

As for the "great backwards FET conspiracy", Kenwood has specifically 
addressed this point and stated that the FET's are correct as installed 
for the specific units they are installed in.  They do NOT advise 
reversing "your" unit to match some documentation that may or may not be 
correct for your particular unit.   This is akin to the old trick of 
putting a preamp in front of your receiver.  The S-Meter reads "10 dB 
higher" than it did before, so it must be helping, never noticing that 
the background noise came up 20 dB and the dynamic range and blocking 
went to pot.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
<http://hr99.home.mindspring.com/R-4C_Servicez/>



Jeff King wrote:

>Dear Traian YO9FZS
>
>I am really impressed a grateful with your reply. Thanks very much.
>
>1. Clearly in your photograph C159 and R152 is missing on your board. 
>
>2. Re circuit diagram. In my First Edition paper copy of the service
>manual.
>It shows R118  as 4.7K between Q13 and L17 to C96
>
>Then in Revised Edition service manual (I got off the internet), and you
>are right R118 has been removed from the circuit.
>Kenwood never mentioned this in any of the Service Bulletins I found on
>the internet.
>
>Unfortunately neither service manual states a publication date
>
>
>3.
>R152 is: 
>- in First Edition service manual,
>- in Revised Edition service manual,
>- not on my IF Board Serial number 6030687 imported from USA
>- on my spare IF board from Serial number 7xxxxxxx imported from USA.
>
>4. 
>C129
>- in First Edition service manual,
>- NOT in Revised Edition service manual, [R153 is now drawn where C129
>used to be drawn]
>- not on my IF Board Serial number 6030687 imported from USA
>- on my spare IF board from Serial number 7xxxxxxx imported from USA.
>
>
>I am still not convinced that R152 should be missing.
>I agree it maybe more than a coincidence that it is missing on both our
>boards dated 1985 and March 1986. Apparently Kenwood assembled radios at
>different assembly plants. Some assembly plants did modifications before
>other assembly plants. So it is possible to have a later serial number
>radio without factory modifications, where an earlier serial number has
>the factory modifications.
>
>I will wait to see if anyone else knows about why Resistor 152 is
>missing.
>
>Have you tried the PY1NR reversing of the field effect transistors? If
>so did produce much gain for you?
>
>Yours sincerely
>Jeff ZL4AI
>
>
>
>
>
>-----Original Message-----
>From: Traian Belinas [mailto:traian at deck.ro] 
>Sent: Tuesday, 8 March 2005 5:03 a.m.
>To: jaking at es.co.nz
>Subject: Re: [Kenwood] TS-940 missing resistror on IF Board, anyone know
>why?
>
>Dear Jeff,
>
>I have bought used defective TS940SAT from VE and had repaired it.
>I took some pictures during that time.
>Your post made me curious, and as no one had answer yet, I have checked
>here
>and the following are my findings regarding it:
>
>1) Looking on my service manual (W7FG copy), I could find a R117 at Q13
>source and a R119 at Q13 drain resistors on the IF unit diagram, but
>could
>not find a R118 at that stage on the diagram (but had no time for
>looking
>very carrefully at other parts of the IF Unit diagram).
>
>2) Looking on the same diagram, I could find R152 at D49 cathode but not
>the
>C129 (it shall be at the Q21/Q22 AGC detector/amplifier stages, but it
>isn't).
>I have found a picture I had take from the IF unit during the trcvr
>repair
>and searched carrefully for the C129 and R152.
>I had cut  the interresting part of it, it is attached here; zoom out
>for
>better seeing it. See that the places labeled C129 and R152
>respectivelly
>are empty; the place marking and the holes for the C129 can be seen.
>The R152 and the C129 are not fitted on my TS940 IF board indeed, even
>if
>the R152 apears on the diagram/schematic.
>
>So, all of your findings are confirmed and I don't think that these are
>manufacturing problems, but rather mods implemented during the
>manufacture
>or Service Bulletins.
>
>The serial number of my 940 is 602xxxxx, a some early one (the oldest
>are
>5xxxxx S/N '83 manufacture and the latest are 1xxxxx '89 manufacture
>date)
>but I saw that it include some mods (including Kenwood Service
>Bulletins),
>some of them made by previous owner.
>
>Hope this to be of help to you.
>
>GL & All the Best,
>Greetings from Bucharest, Romania,
>73,
>Traian, YO9FZS
>
>
>jaking at es.co.nz wrote:
>
>  
>
>>1.
>>While looking for a fault on the IF Board , I noticed that Resistor
>>    
>>
>118
>  
>
>>in the 4th IF amp is missing, and foil is soldered over indicating it
>>was never installed.
>>
>>When I checked on another IF board, (I have access too) Resistor 118
>>    
>>
>has
>  
>
>>also never been installed there.
>>
>>Does anyone know if Kenwood deliberately missed Resistor 118 out? or
>>removed it?
>>
>>2.
>>I have also found Capacitor 129 and Resistor 152 missing from this IF
>>board. These seem like serious mistakes during production and I will
>>    
>>
>put
>  
>
>>them back in unless anyone can explain why they are missing.
>>
>>Has anyone found that some TS-940s come with components missed out
>>during production assembly: If so could you please tell which parts
>>    
>>
>are
>  
>
>>not installed.
>>
>>I would appreciate all and any comments.
>>
>>Yours sincerely
>>
>>Jeff ZL4aI
>>    
>>
>  
>