[Kenwood] Removing AVR board from TS-940 for troubleshooting

[Clif]

You need to resolder the connections on the AVR board connecting to D1, D2,
CN1, CN2. Then remove the connector from Q103 and solder the wires to the
transistor. Also look over the AVR board for crystallized solder
connections especially around D10-13. Any of the large caps that have a
bulged top need to be replaced. If you ignore this the failure mode will
not be pretty.


On Tue, Apr 15, 2014 at 6:24 PM, Dennis Younker NE6I <NE6I at cox.net> wrote:

> Dave, I have an intermittent problem that sounds an awful lot like yours. I
> describe it as a motorboat sound. I have found that the intermittent
> problem
> is at connector 2 on the AVR board.  This is a 3-pin connector with yellow,
> green and blue wires as viewed from front to back of the radio. Wiggling it
> solves the problem for weeks or months. One of these days I need to look
> closer at that connector and see if I can permanently fix it or replace it.
> Or bypass it as Clif suggests.
>
> By the way, this connector ties to Q103.
>
> --Dennis NE6I
>
> -----Original Message-----
> From: kenwood-bounces at mailman.qth.net
> [mailto:kenwood-bounces at mailman.qth.net] On Behalf Of Clif
> Sent: Tuesday, April 15, 2014 4:00 PM
> To: David Feldman
> Cc: Kenwood Mail List
> Subject: Re: [Kenwood] Removing AVR board from TS-940 for troubleshooting
>
> Solder the wires to Q103. The connector has failed.
>
>
> On Tue, Apr 15, 2014 at 5:29 PM, David Feldman <wb0gaz at yahoo.com> wrote:
>
> >
> > Thank you, Clif,
> >
> > Here are details:
> >
> > TS940SAT S/N 7 million, no prior service issues
> >
> > Press power button, getting a rattle/buzz sound (~20 Hz) from
> > near/below the main power transformer (didn't remove bottom cover to
> > investigate further), no lights/LEDs, no control panel response, no
> > audio from speaker, meter in any select position displaying ~S5 with bit
> of vibration.
> >
> > Q103 (2SD1266 regulator pass device) Emitter should be 23.2, measure
> > 8.7
> > Q103 (2SD1266 regulator pass device) Base should be 23.8, measure 21.3
> > Q103 (2SD1266 regulator pass device) Collector should be 30.0, measure
> > 33.0
> >
> > Q104 (2SD1406 regulator pass device) Emitter should be 8.0, measure
> > 2.1
> > Q104 (2SD1406 regulator pass device) Base should be 8.7, measure 2.8
> > Q104 (2SD1406 regulator pass device) Collector should be 11.6, measure
> > 17.0
> >
> > 7805 regulator device input should be 8V, measure 2.18V
> > 7805 regulator device common should be 0V, measure 0V
> > 7805 regulator device output should be 5V, measure 0.6V
> >
> > No smoke/heating symptoms
> > No visual damage
> >
> > Collector pass regulator seems normal 28.3V out
> >
> > Radio was on loan to a friend when it failed, he indicated the buzzing
> > symptom came on intermittently at first, then permanently.
> >
> > Thanks!
> >
> > Dave
> >
> >
> > ------------------------------
> > On Tue, Apr 15, 2014 11:10 AM MDT Clif wrote:
> >
> > >Describe your problem.
> > >
> > >
> > >On Tue, Apr 15, 2014 at 12:01 PM, David Feldman <wb0gaz at yahoo.com>
> wrote:
> > >
> > >>
> > >> I am preparing to troubleshoot/fix TS-940 which appears to have
> > developed
> > >> problem in low voltage rectifier/filter/regulator section of AVR
> board.
> > Can
> > >> I unscrew the four screws holding the AVR board to chassis and prop
> > >> the board up so I can access PC traces to take measurements? Does
> > >> the TS-940 AVR board rely on the screws/standoffs for ground?
> > >>
> > >> Thanks,
> > >>
> > >> 73 Dave WB0GAZ wb0gaz at yahoo.com
> > >>
> > >> ______________________________________________________________
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> > >>
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> > >>
> > >
> > >
> > >
> > >--
> > >Clif Holland KA5IPF
> > >www.avvid.com
> >
> >
>
>
> --
> Clif Holland KA5IPF
> www.avvid.com
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>
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-- 
Clif Holland KA5IPF
www.avvid.com