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

[Dennis Younker NE6I]

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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