[Kenwood] TS-930 Sensitivity

[WILLIAM VICENT]

Clif,

Thanks for the insight.

I have the Service Manual but it's missing the schematic of the Signal Unit
(I do have the component locator) so I'm having some trouble ID'ing the band
diodes.  Related problem is checking ther vertically mounted diodes when you
can't get at metal on the board side of the diode.  Do you have a readable
schematic for that section of the board?

To clarify my previous question:  Is a reading of -125 dB sensitivity
acceptable?  Some of the bands are at -135 and -140.

Regards, Jim K2SZ


----- Original Message -----
From: "Clif Holland" <clif at avvid.com>
To: "Jim Dicso" <dicso123 at hotmail.com>; <kenwood at mailman.qth.net>
Sent: Tuesday, January 04, 2005 4:39 PM
Subject: Re: [Kenwood] TS-930 Sensitivity


> Most likely it is the ATT relays. They are good about being intermittent.
> There are NO plated thru holes on the Signal unit of the 930 so that's
out.
>
> Don't even think about trying to align the filters with less than a
network
> analyzer. The odds of that being the problem are slim to none and the odds
> of misaligning the filter is almost 100%.
>
> Leaky diodes are easy to find, compare the voltages on each side to known
> good ones. It also will locate open ones. While there make sure that only
> one set of filters is turned on at a time. An intermittent connection in
the
> logic to the signal unit can turn on 2 at once and it will behave almost
> exactly as described.
>
>
> Clif Holland, KA5IPF
> www.avvid.com
>
>
> ----- Original Message -----
> From: "Jim Dicso" <dicso123 at hotmail.com>
> To: <kenwood at mailman.qth.net>
> Sent: Tuesday, January 04, 2005 11:46 AM
> Subject: [Kenwood] TS-930 Sensitivity
>
>
> I have sensitivity problems on at least two bands in a TS-930 (one of two
> that I have in the shack).
>
> I've followed the previous work on improving TS-930's and planned to
replace
> suspect PIN diodes.  However, I couldn't resolve part #'s from PDF
versions
> of the Signal Board so I was testing all the suspect diodes with a
digitial
> multimeter and signal injection and range switching.  Unfortunately, in
> order to reach all the test points (and to replace the diodes), it looks
> like lot's of screws and cables need to be removed.
>
> I took a step back and measured sensitivity on both units for all bands
> using an HP 8640B and min discernible signal (speaker).
> ....somewhat subjective but questionable readings were doublechecked.
> Originally, this test produced low (approx -75db) sensitivity on 18.1 and
> 14.2 Mhz but this comparison produced no readings higher than -125db.
>
> Has this problem surfaced because of thru hole problems?   (I could have
> changed the contact by probing)
>
> Is this now an alignment problem?  Will BPF tuning help me get to the -135
> dB/-140 dB sensitivity I found on many bands?
>
> Thanks, Jim K2SZ
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