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

[Jeff King]

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
>
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