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28276Re: [softrock40] Re: Troubleshooting Softrock lite RX

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  • Jose Bonanca
    Dec 1, 2008
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      Well Tony I have here some LT6241 and they are different from LT6231..
      So , now are you sure?
      Regards.


       
      On Mon, Dec 1, 2008 at 8:34 PM, Tony Parks <kb9yig@...> wrote:

      Hi Norman,
       
      The TLC6241CS8 should do the job if the op-amp is needing to be replaced.
       
      73,
      Tony KB9YIG
      ----- Original Message -----
      Sent: Monday, December 01, 2008 3:05 PM
      Subject: [softrock40] Re: Troubleshooting Softrock lite RX

      Thanks Tony.

      It all checks out visually so I'll take out the capacitors tomorrow
      and see what happens.

      I'll probably order up a new U5 just in case. Our local stockist
      lists 3 versions of the LTC6241, with numbers LTC6241CS8,
      LTC6241HVCS8 and LTC6241HVIS8. The first two seem to be identical
      except for a wider temperature range for the second - both are
      described as type "low noise". The third is decribed as
      type "CMOS". Does it matter which I get?

      Norman

      --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@...> wrote:
      >
      > Hi Norman,
      >
      > With DC gain of each op-amp about right, it seems that R9 has a
      larger resistance than 10 ohms, or C14 has more capacitance than 220
      pF, or there is an AC load on the pin 1 output of U5. (Also still
      the possibility there is a problem with U5.) I would suggest
      removing C16 first to see if the AC voltage at pin 1 of U5 increases
      with the RF test signal input you are using. Next, remove C14.
      >
      > 73,
      > Tony KB9YIG
      >
      > ----- Original Message -----
      > From: norman.billingham
      > To: softrock40@yahoogroups.com
      > Sent: Monday, December 01, 2008 1:27 PM
      > Subject: [softrock40] Re: Troubleshooting Softrock lite RX
      >
      >
      >
      >
      > Hi Tony
      >
      > There is a fine strong signal on pin 7 and on the output side of
      the
      > capacitor. There is no signal at all on pin 1 or on the output
      lead.
      >
      > All measured wrt ground at the screen connection for I and Q
      lines.
      >
      > Only load is the scope probe - at the moment I just have bits of
      wire
      > soldered into the I and Q outputs to provide test points before I
      > mount the board properly in a box and put in the audio cable.
      >
      > Thanks for all the help
      >
      > 73 Norman
      >
      > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
      > >
      > > Hi Norman,
      > >
      > > The DC gain of each of op-amp is about right.
      > >
      > > When you checked for the AC I and Q outputs was it at pins 1
      and 7
      > of the dual op-amp each with reference to circuit ground or at
      the
      > tip and ring connections beyond SMT caps C16 and C17? Also, what
      > load did you have on the I and Q output lines?
      > >
      > > 73,
      > > Tony KB9YIG
      > > ----- Original Message -----
      > > From: norman.billingham
      > > To: softrock40@yahoogroups.com
      > > Sent: Monday, December 01, 2008 11:44 AM
      > > Subject: [softrock40] Re: Troubleshooting Softrock lite RX
      > >
      > >
      > >
      > > Hi Tony
      > >
      > > pin 1 goes from 2.49 to 3.73V with 10K at pin 2
      > >
      > > pin 7 goes from 2.49 to 3.89 with 10K at pin 6
      > >
      > > Norman
      > >
      > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
      > > >
      > > > Hi Norman,
      > > >
      > > > Please repeat the DC gain test for the dual op-amp. A 10k
      > resistor
      > > to ground at pin 2 or pin 6 should result in a voltage change
      of
      > 1.25
      > > volts at pin 1 or pin 7 respectively.
      > > >
      > > > 73,
      > > > Tony KB9YIG
      > > > ----- Original Message -----
      > > > From: norman.billingham
      > > > To: softrock40@yahoogroups.com
      > > > Sent: Monday, December 01, 2008 10:20 AM
      > > > Subject: [softrock40] Re: Troubleshooting Softrock lite RX
      > > >
      > > >
      > > > Hi Tony
      > > >
      > > > Thanks for coming back so fast
      > > >
      > > > This is a 6.0 board so I assume you mean C12 and C13, the two
      > > 0.047
      > > > uF decouplers? With my scope AC coupled and on its best
      > > sensitvity,
      > > > and 50mV of RF on the input all I can see there (or at pins 7
      > and
      > > 9
      > > > of U4) is about 20 mV of local oscillator frequency. Likewise
      > at
      > > > pins 2 and 6 of U5.
      > > >
      > > > Pin 1 of U5 is producing nothing and pin 7 has a nice strong
      Q
      > > signal
      > > > at just the right audio frequency.
      > > >
      > > > 73
      > > >
      > > > Norman
      > > >
      > > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@>
      wrote:
      > > > >
      > > > > Hi Norman,
      > > > >
      > > > > How do the signals look on C11 and C13 with reference to
      > > circuit
      > > > ground when you have an RF input to the antenna terminals?
      > > > >
      > > > > 73,
      > > > > Tony KB9YIG
      > > > > ----- Original Message -----
      > > > > From: norman.billingham
      > > > > To: softrock40@yahoogroups.com
      > > > > Sent: Monday, December 01, 2008 7:32 AM
      > > > > Subject: [softrock40] Re: Troubleshooting Softrock lite RX
      > > > >
      > > > >
      > > > > Dear Tony
      > > > >
      > > > > OK I'm really lost now.
      > > > >
      > > > > Carefully checked all component values and soldering of T1
      > > leads -
      > > >
      > > > > all seems OK. Checked all leads and for solder bridges with
      > > high
      > > > > magnification and all seems OK.
      > > > >
      > > > > With no power and no signal there is continuity between the
      > two
      > > > ends
      > > > > of T1. There is 20 ohms between pins 11 and 12 of U4 and
      also
      > > > > between pins 3 and 6.
      > > > >
      > > > > There is 774 ohms between CT of T1 and pin 8 of U5, and
      > > > essentially
      > > > > zero ohms between CT of T1 and pins 3 and 5 of U5.
      > > > >
      > > > > With no power and 1V p/p at 7.1MHz on the antenna there are
      > > > > symmetrical 450mV signals 180 out of phase at 11/2 and at
      3/6
      > > on
      > > > U4 -
      > > > > all suggests T1 is OK.
      > > > >
      > > > > With power on the board and no signal, there is 5.4V p/p at
      > > 7.15
      > > > MHZ
      > > > > on the two test points on the board - square wave and 90
      > phase
      > > > > shifted and these signals are also on pins 2 and 14 of U4.
      > > > >
      > > > > With power on and around 50 mV ont he antenna at 7.15 Mhz
      > there
      > > > is
      > > > > about 1V of AF on the Q line and essentially nothing on the
      I
      > > > line.
      > > > >
      > > > > When I measured the voltahes around U%, all were OK but
      > > > the "normal"
      > > > > values (both 2.47V) both went to 4.93 when a 2.6K resistor
      > was
      > > > used
      > > > > to bridge the inputs - Robbie's program predicts 3.41V.
      > > > >
      > > > > Is it possible that one channel of U5 just isn't working?
      or
      > is
      > > > > there some other possible fault?
      > > > >
      > > > > Any ides gratefully received
      > > > >
      > > > > TIA
      > > > >
      > > > > Norman
      > > > >
      > > > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@>
      > wrote:
      > > > > >
      > > > > > Hi Norman,
      > > > > >
      > > > > > Please check the soldering around T1 and make sure the
      > > resistor
      > > > > values are according to the schematic.
      > > > > >
      > > > > > 73,
      > > > > > Tony KB9YIG
      > > > > > ----- Original Message -----
      > > > > > From: norman.billingham
      > > > > > To: softrock40@yahoogroups.com
      > > > > > Sent: Sunday, November 30, 2008 12:53 PM
      > > > > > Subject: [softrock40] Troubleshooting Softrock lite RX
      > > > > >
      > > > > >
      > > > > > Dear all
      > > > > >
      > > > > > Hopefully someone can offer words of help to a non-expert.
      > > > > >
      > > > > > I just finished my second softrock, using a V6.0 kit I've
      > had
      > > > for
      > > > > a
      > > > > > while.
      > > > > >
      > > > > > When I inject about 50mV of signal into the antenna at
      > about
      > > > > 16kHz
      > > > > > off centre, I get a beautiful sine wave at both I and Q
      and
      > > 90o
      > > > > phase
      > > > > > shift but the p/p voltage on Q is about 3.5 V and on I is
      > > only
      > > > > around
      > > > > > 50mV.
      > > > > >
      > > > > > I followed the detailed instructions and tests on
      WB5RVZ's
      > > > great
      > > > > > pages and all checked out OK except for:
      > > > > >
      > > > > > The op-amps. All voltages were OK but the "normal" values
      > > (both
      > > > > > 2.47V) both went to 4.93 when a 2.6K resistor was used to
      > > > bridge
      > > > > the
      > > > > > inputs - Robbie's program predicts 3.41V
      > > > > >
      > > > > > I measure 500mV at pins 1 and 15 on the mixer where
      > Robbie's
      > > > > values
      > > > > > are 45 mV - looking at the circuit, these pins are both
      on
      > an
      > > > > 1/11K
      > > > > > potential divider from the 5V rail and 500mV is the
      > > calculated
      > > > > value.
      > > > > >
      > > > > > I've checked all the component values and soldering
      around
      > > the
      > > > op
      > > > > > amps and can't find a problem.
      > > > > >
      > > > > > Anyone any good ideas please?
      > > > > >
      > > > > > Thanks in advance
      > > > > >
      > > > > > Norman (M0EBI)
      > > > > >
      > > > >
      > > >
      > >
      >




      --
      Jose Bonanca  (CT1aos)
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