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Re: [TenTec] TenTec Digest, Vol 192, Issue 26

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] TenTec Digest, Vol 192, Issue 26
From: MadScientist <dukeshifi@comcast.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 30 Dec 2018 15:50:01 -0600
List-post: <mailto:tentec@contesting.com>
When diodes such as PIN diodes are placed in series, the signal isolation 
improves in the off state but makes little difference in on state signal loss.

Gary

> On Dec 30, 2018, at 1:50 PM, wes Bolin <k5apl41@gmail.com> wrote:
> 
> Hi Gary
> Sorry, I was using ambiguous description of the problem location.  I am
> referring to the Bandpass Filter Board 81409 that includes RF
> Preamplification.
> 
> I understand that dodes in series increase PIV protection, but see no need
> for this in the low level receive line ........That's one thing I'm curious
> about.  Other thing
> is the transistor function.....it sure did attenuate the signals with a B
> to C short circuit.....it got hot too.  Why  did it not get documented
> anywhere?
> The transistor might have been added by the factory since the base lead is
> going through a hole drilled in the circuit board, while the Emitter and
> Collector were soldered
> onto component leads above the board.
> 
> I am going to put a new transistor back in the radio and see what happens.
> Thanks for your comments,
> Wes
> 
> 
> 
> 
> 
> On Sun, Dec 30, 2018 at 11:00 AM <tentec-request@contesting.com> wrote:
> 
>> Send TenTec mailing list submissions to
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>> 
>> 
>> Today's Topics:
>> 
>>   1. Re: TenTec Digest, Vol 192, Issue 25 (wes Bolin)
>>   2. Re: TenTec Digest, Vol 192, Issue 25 (MadScientist)
>>   3. Re: Omni VI+: low TX and RX on 12 meters (Phil Erickson)
>>   4. Re: TenTec] Omni VI+: low TX and RX on 12 meters (Peter Bertini)
>> 
>> 
>> ----------------------------------------------------------------------
>> 
>> Message: 1
>> Date: Sat, 29 Dec 2018 13:03:32 -0600
>> From: wes Bolin <k5apl41@gmail.com>
>> To: tentec@contesting.com
>> Subject: Re: [TenTec] TenTec Digest, Vol 192, Issue 25
>> Message-ID:
>>        <
>> CALM7jM6_OjGwUxDp0xegHfabzHnXM4QUQ_sK4cQ+zomuq+Oy8g@mail.gmail.com>
>> Content-Type: text/plain; charset="UTF-8"
>> 
>> Halleluyah I found the problem!
>> 
>> The circuitry is still a puzzle to me so hopefully someone can shed some
>> light on it:
>> 
>> The Diode D10 on the Front End Board is actually two small diodes in series
>> in my radio.  The junction of the two individual diodes the Collector of a
>> MPS6514 NPN transistor soldered to it. The
>> transistor Emitter is soldered to the Jumper near C65, C66, and  Base is
>> soldered into a hole on the circuit board.  The transistor is not in any
>> documentation that I can find and the need to double up the diodes is not
>> documented either.  The transistor was getting hot to my touch, so
>> Unsoldered the Emitter and still hot, so unsoldered the Collector.  This
>> allowed the signal path to not be attenuated any longer and the radio's
>> sensitivity is back to normal.
>> 
>> Questions:
>> 1.  Why double dodes?
>> 2.  Why the transistor?
>> 3.  Do I need to replace the transistor or leave it out of the circuit?
>> 
>> All receive signals go through D10, so it was where the Receive signal was
>> being attenuated.
>> Wes
>> 
>> On Sat, Dec 29, 2018 at 11:00 AM <tentec-request@contesting.com> wrote:
>> 
>>> Send TenTec mailing list submissions to
>>>        tentec@contesting.com
>>> 
>>> To subscribe or unsubscribe via the World Wide Web, visit
>>>        http://lists.contesting.com/mailman/listinfo/tentec
>>> or, via email, send a message with subject or body 'help' to
>>>        tentec-request@contesting.com
>>> 
>>> You can reach the person managing the list at
>>>        tentec-owner@contesting.com
>>> 
>>> When replying, please edit your Subject line so it is more specific
>>> than "Re: Contents of TenTec digest..."
>>> 
>>> 
>>> Today's Topics:
>>> 
>>>   1. OMNI V Failed (wes Bolin)
>>> 
>>> 
>>> ----------------------------------------------------------------------
>>> 
>>> Message: 1
>>> Date: Fri, 28 Dec 2018 15:41:39 -0600
>>> From: wes Bolin <k5apl41@gmail.com>
>>> To: tentec@contesting.com
>>> Subject: [TenTec] OMNI V Failed
>>> Message-ID:
>>>        <CALM7jM50KHwghA8gtYw5o36rrm6q+1iddJcJngNygL8GM5-=
>>> rA@mail.gmail.com>
>>> Content-Type: text/plain; charset="UTF-8"
>>> 
>>> Worked OK, turned it off.  Next day it turned on but no Receive.  It
>>> belongs to my friend so I brought it home to troubleshoot.  What I know
>> is:
>>> 1.  It was intermittently working when it was turned on--sometimes the
>>> display did not light up, other LEDs were On randomly....I found that the
>>> N4PY chip was probably the problem after reading the book.  I put the
>>> original chip back in and it turns On nicely. good display, etc.  (A
>>> replacement N4PY chip is coming).
>>> 2.  The radio transmits OK; power out and SSB all seem good
>>> 3.  I tested the TRX-RX switch with Ohmmeter and it is switching OK
>>> 4.  In RX Ant I get much stronger signal through the radio than in the
>> TRX
>>> Ant
>>> connector on Receive.  On 14MHz the signal drops into the noise at about
>> 20
>>> microvolts in the RX input.  Even with S-meter well over S-9 (+30) with
>> the
>>> RX
>>> input, I can hear it S1 or so through the TRX input.
>>> 
>>> So the receiver is pretty deaf with the RX input and unusable with the
>> TRX
>>> input.
>>> 
>>> 5.  The Attenuator works with the receive signals
>>> 6.  I have tried 80M and 20M so its not band dependent
>>> 7.  Measured voltages and they are correct
>>> I suspect that my friend turned the radio Off and On by leaving the OMNI
>> V
>>> "On" and switching  the Power Supply  (Book says don't do this).  I'm
>>> guessing a transient took out the microprocessor, and caused the RX
>>> problem.
>>> 
>>> Any help or  ideas will be greatly appreciated.
>>> 73
>>> Wes
>>> 
>>> 
>>> ------------------------------
>>> 
>>> Subject: Digest Footer
>>> 
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>> 
>>> 
>>> ------------------------------
>>> 
>>> End of TenTec Digest, Vol 192, Issue 25
>>> ***************************************
>>> 
>> 
>> 
>> ------------------------------
>> 
>> Message: 2
>> Date: Sat, 29 Dec 2018 13:35:23 -0600
>> From: MadScientist <dukeshifi@comcast.net>
>> To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>> Subject: Re: [TenTec] TenTec Digest, Vol 192, Issue 25
>> Message-ID: <744004E7-249F-4BB1-B0CC-296FAB04D24A@comcast.net>
>> Content-Type: text/plain;       charset=us-ascii
>> 
>> The use of dual diodes is likely an attempt to improve isolation at this
>> point and also to allow use of that transistor to pull the signal point to
>> ground, thereby improving attenuation here.
>> 
>> Are you talking the band pass tuning board or RF front end? The manual
>> list no such board named RF front end.
>> 
>> Gary
>> 
>>> On Dec 29, 2018, at 1:03 PM, wes Bolin <k5apl41@gmail.com> wrote:
>>> 
>>> Halleluyah I found the problem!
>>> 
>>> The circuitry is still a puzzle to me so hopefully someone can shed some
>>> light on it:
>>> 
>>> The Diode D10 on the Front End Board is actually two small diodes in
>> series
>>> in my radio.  The junction of the two individual diodes the Collector of
>> a
>>> MPS6514 NPN transistor soldered to it. The
>>> transistor Emitter is soldered to the Jumper near C65, C66, and  Base is
>>> soldered into a hole on the circuit board.  The transistor is not in any
>>> documentation that I can find and the need to double up the diodes is not
>>> documented either.  The transistor was getting hot to my touch, so
>>> Unsoldered the Emitter and still hot, so unsoldered the Collector.  This
>>> allowed the signal path to not be attenuated any longer and the radio's
>>> sensitivity is back to normal.
>>> 
>>> Questions:
>>> 1.  Why double dodes?
>>> 2.  Why the transistor?
>>> 3.  Do I need to replace the transistor or leave it out of the circuit?
>>> 
>>> All receive signals go through D10, so it was where the Receive signal
>> was
>>> being attenuated.
>>> Wes
>>> 
>>> On Sat, Dec 29, 2018 at 11:00 AM <tentec-request@contesting.com> wrote:
>>> 
>>>> Send TenTec mailing list submissions to
>>>>       tentec@contesting.com
>>>> 
>>>> To subscribe or unsubscribe via the World Wide Web, visit
>>>>       http://lists.contesting.com/mailman/listinfo/tentec
>>>> or, via email, send a message with subject or body 'help' to
>>>>       tentec-request@contesting.com
>>>> 
>>>> You can reach the person managing the list at
>>>>       tentec-owner@contesting.com
>>>> 
>>>> When replying, please edit your Subject line so it is more specific
>>>> than "Re: Contents of TenTec digest..."
>>>> 
>>>> 
>>>> Today's Topics:
>>>> 
>>>>  1. OMNI V Failed (wes Bolin)
>>>> 
>>>> 
>>>> ----------------------------------------------------------------------
>>>> 
>>>> Message: 1
>>>> Date: Fri, 28 Dec 2018 15:41:39 -0600
>>>> From: wes Bolin <k5apl41@gmail.com>
>>>> To: tentec@contesting.com
>>>> Subject: [TenTec] OMNI V Failed
>>>> Message-ID:
>>>>       <CALM7jM50KHwghA8gtYw5o36rrm6q+1iddJcJngNygL8GM5-=
>>>> rA@mail.gmail.com>
>>>> Content-Type: text/plain; charset="UTF-8"
>>>> 
>>>> Worked OK, turned it off.  Next day it turned on but no Receive.  It
>>>> belongs to my friend so I brought it home to troubleshoot.  What I know
>> is:
>>>> 1.  It was intermittently working when it was turned on--sometimes the
>>>> display did not light up, other LEDs were On randomly....I found that
>> the
>>>> N4PY chip was probably the problem after reading the book.  I put the
>>>> original chip back in and it turns On nicely. good display, etc.  (A
>>>> replacement N4PY chip is coming).
>>>> 2.  The radio transmits OK; power out and SSB all seem good
>>>> 3.  I tested the TRX-RX switch with Ohmmeter and it is switching OK
>>>> 4.  In RX Ant I get much stronger signal through the radio than in the
>> TRX
>>>> Ant
>>>> connector on Receive.  On 14MHz the signal drops into the noise at
>> about 20
>>>> microvolts in the RX input.  Even with S-meter well over S-9 (+30) with
>> the
>>>> RX
>>>> input, I can hear it S1 or so through the TRX input.
>>>> 
>>>> So the receiver is pretty deaf with the RX input and unusable with the
>> TRX
>>>> input.
>>>> 
>>>> 5.  The Attenuator works with the receive signals
>>>> 6.  I have tried 80M and 20M so its not band dependent
>>>> 7.  Measured voltages and they are correct
>>>> I suspect that my friend turned the radio Off and On by leaving the
>> OMNI V
>>>> "On" and switching  the Power Supply  (Book says don't do this).  I'm
>>>> guessing a transient took out the microprocessor, and caused the RX
>>>> problem.
>>>> 
>>>> Any help or  ideas will be greatly appreciated.
>>>> 73
>>>> Wes
>>>> 
>>>> 
>>>> ------------------------------
>>>> 
>>>> Subject: Digest Footer
>>>> 
>>>> _______________________________________________
>>>> TenTec mailing list
>>>> TenTec@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>> 
>>>> 
>>>> ------------------------------
>>>> 
>>>> End of TenTec Digest, Vol 192, Issue 25
>>>> ***************************************
>>>> 
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>> 
>> 
>> 
>> ------------------------------
>> 
>> Message: 3
>> Date: Sat, 29 Dec 2018 15:40:57 -0500
>> From: Phil Erickson <phil.erickson@gmail.com>
>> To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>> Subject: Re: [TenTec] Omni VI+: low TX and RX on 12 meters
>> Message-ID:
>>        <CAAZaqEtU6h3uoiFP=
>> FEgTpXN8uDOzj5f3LzGSh4YrQVJLAyHBA@mail.gmail.com>
>> Content-Type: text/plain; charset="UTF-8"
>> 
>> Hi all,
>> 
>>  More investigation has narrowed the problem to the BPF/front end board
>> 81593.  We'll use 15 and 10 meters as our "working normally" and 12 meters
>> as "working abnormally" for this discussion:
>> 
>> - LO input from the XO-LO board at connector 26 is at exactly the right
>> appropriate frequency for a 9 MHz IF, and nearly constant voltage for
>> 15/12/10 meters.  That eliminates the XO-LO board as the problem (relief!).
>> - TX input at connector 27 is also nearly identical on 15/12/10 meters.
>> - However, the output at connector 24, which goes off to the low level
>> driver board, is not the same for all three.
>> 
>> Using a 1 Mohm input impedance on a Tek 2465A scope:
>> 
>> 15, 10 meters:  in TUNE mode, signal increases with PWR knob up to
>> about +/- 2V at three dots up from minimum (10:30 am clock position) and
>> then essentially saturates
>> 12 meters: in TUNE mode, signal increases with PWR knob but only up to
>> about +/- 0.12V at three dots up from minimum and then essentially
>> saturates
>> 
>>  Not sure why the signal is saturating at the 10:30 am position as I would
>> have figured it would go up as I turned PWR up further.  (It does go up to
>> a clean 90 watts or so on 15 and 12 meters when everything is hooked back
>> together.)  No matter; the problem is clearly in low output at 12 meters
>> from 81593.
>> 
>>  Since 81593 has individual BPFs for each band that are used for both TX
>> and RX, my guess is that the BPF is off frequency for 12 meters which would
>> explain why I have a relatively deaf receiver by 20 dB on that band as well
>> as low TX output.
>> 
>>  Now the next question to this group: does anyone have the alignment
>> procedure for a 81593 BPF/front end board?  The manual does not describe
>> one.  I am also very careful about adjusting slugs as like many of you,
>> I've had inductor cores snap in two with too much pressure, so I want to do
>> the minimal amount of tweaking to fix the problem and not do too much
>> "golden screwdriver" wiggling back and forth.  Knowing what to inject and
>> where to inject it would be great.  (I have HP signal generators and the
>> like available.)
>> 
>>  This list is really terrific - and thanks to Gary W0DVN and Pete in
>> particular!
>> 
>> 73
>> Phil W1PJE
>> 
>> 
>> ------------------------------
>> 
>> Message: 4
>> Date: Sun, 30 Dec 2018 10:33:25 -0500
>> From: Peter Bertini <radioconnection@gmail.com>
>> To: tentec@contesting.com
>> Subject: Re: [TenTec] TenTec] Omni VI+: low TX and RX on 12 meters
>> Message-ID:
>>        <
>> CA+uDY2SARwO74o0z48Y4QpDCjPJjz6zfREqahQ5xVia2mej6pg@mail.gmail.com>
>> Content-Type: text/plain; charset="UTF-8"
>> 
>> Phil
>> 
>> Do NOT attempt to realign those passband filters!  Normal aging will not
>> give you a 20 dB signal loss.  Alignment can mask other problems and can
>> compound finding a resolution for your problem.  Realignment would problem
>> require a sweep generator, or at worst, hours of tedious stagger tuning
>> while manually sweeping the response curves.
>> 
>> A high Z scope is fine, since you are tracing 50 ohm signal paths it will
>> not load the circuits.
>> 
>> Getting back to your problem:  do what Gary suggested. Carefully resolder
>> all of the connections for the components in that particular filter. You
>> might want to first verify that the associated switching diodes are indeed
>> being forward biased when that band range is selected! It could be as
>> simple as the diodes not being switched on.
>> 
>> I had a similar passband filter failure in LO system. No fun.
>> 
>> regards
>> 
>> Peter k1zjh
>> 
>> 
>> ------------------------------
>> 
>> Subject: Digest Footer
>> 
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>> 
>> 
>> ------------------------------
>> 
>> End of TenTec Digest, Vol 192, Issue 26
>> ***************************************
>> 
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