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Ensemble RX II another newbie Si570 chip question...

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  • Tavi
    I m at the point in the build where I m supposed to be able to change frequencies on the Si570 chip. I m seeing a very nasty 40MHz waveform with a lot of
    Message 1 of 6 , Feb 24, 2013
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      I'm at the point in the build where I'm supposed to be able to change frequencies on the Si570 chip. I'm seeing a very nasty 40MHz waveform with a lot of jitter and an on/off type envelope. Acording to CFGSR, the chip is talking to the computer. Looking at pins 7 and 8 with a scope show them sitting high and quiet except when data is coming from the AVR chip. There is no visual or scope evidence that any pins are bridged as far as I can tell. Strangely, when I am changing frequency with my mouse wheel I see a "ghost image" of a signal on the scope that appears to be the chip changing frequency. It immediately reverts back to the crappy 40MHz signal as soon as I stop turning the mouse wheel. Any suggestions before I turn on the heat gun for a chip removal? Thank you very much for any help/suggestions. Additionally, if I need to procure a new Si570 chip, where is the best place to get one? Surprisingly I only saw one on eBay and it was in Bulgaria.
    • Justin Cumberland
      I m sorry I cannot provide the link right off hand but some one sells them in a yahoo store that s linked to this group, 19$ I believe JMC
      Message 2 of 6 , Feb 24, 2013
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        I'm sorry I cannot provide the link right off hand but some one sells them in a yahoo store that's linked to this group, 19$ I believe

        JMC

        On Feb 24, 2013 5:36 PM, "Tavi" <n3ikq@...> wrote:
         

        I'm at the point in the build where I'm supposed to be able to change frequencies on the Si570 chip. I'm seeing a very nasty 40MHz waveform with a lot of jitter and an on/off type envelope. Acording to CFGSR, the chip is talking to the computer. Looking at pins 7 and 8 with a scope show them sitting high and quiet except when data is coming from the AVR chip. There is no visual or scope evidence that any pins are bridged as far as I can tell. Strangely, when I am changing frequency with my mouse wheel I see a "ghost image" of a signal on the scope that appears to be the chip changing frequency. It immediately reverts back to the crappy 40MHz signal as soon as I stop turning the mouse wheel. Any suggestions before I turn on the heat gun for a chip removal? Thank you very much for any help/suggestions. Additionally, if I need to procure a new Si570 chip, where is the best place to get one? Surprisingly I only saw one on eBay and it was in Bulgaria.

      • John Greusel
        Before you do anything drastic go back and read some of the SI570 posts in the past messages. 99 times out of 100 is a faulty solder joint. There is the
        Message 3 of 6 , Feb 24, 2013
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          Before you do anything drastic go back and read some of the SI570 posts in the past messages. 99 times out of 100 is a faulty solder joint. There is the occasional bad SI570 but it's rare- solder problems very common.

          John
          KC9OJV
           



          From: Justin Cumberland <justin.marc.cumberland@...>
          To: softrock40@yahoogroups.com
          Sent: Sunday, February 24, 2013 5:00 PM
          Subject: Re: [softrock40] Ensemble RX II another newbie Si570 chip question...

           
          I'm sorry I cannot provide the link right off hand but some one sells them in a yahoo store that's linked to this group, 19$ I believe
          JMC
          On Feb 24, 2013 5:36 PM, "Tavi" <n3ikq@...> wrote:
           
          I'm at the point in the build where I'm supposed to be able to change frequencies on the Si570 chip. I'm seeing a very nasty 40MHz waveform with a lot of jitter and an on/off type envelope. Acording to CFGSR, the chip is talking to the computer. Looking at pins 7 and 8 with a scope show them sitting high and quiet except when data is coming from the AVR chip. There is no visual or scope evidence that any pins are bridged as far as I can tell. Strangely, when I am changing frequency with my mouse wheel I see a "ghost image" of a signal on the scope that appears to be the chip changing frequency. It immediately reverts back to the crappy 40MHz signal as soon as I stop turning the mouse wheel. Any suggestions before I turn on the heat gun for a chip removal? Thank you very much for any help/suggestions. Additionally, if I need to procure a new Si570 chip, where is the best place to get one? Surprisingly I only saw one on eBay and it was in Bulgaria.



        • Alan
          ... Subject: [softrock40] Ensemble RX II another newbie Si570 chip question... ... If the Si570 is not receiving any good I2C signals it will start at
          Message 4 of 6 , Feb 24, 2013
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            ----- Original Message -----
            Subject: [softrock40] Ensemble RX II another newbie Si570 chip question...


            > I'm at the point in the build where I'm supposed to be able to change frequencies on the Si570 chip. I'm seeing a very nasty 40MHz
            > waveform with a lot of jitter and an on/off type envelope. Acording to CFGSR, the chip is talking to the computer. Looking at pins
            > 7 and 8 with a scope show them sitting high and quiet except when data is coming from the AVR chip. There is no visual or scope
            > evidence that any pins are bridged as far as I can tell. Strangely, when I am changing frequency with my mouse wheel I see a
            > "ghost image" of a signal on the scope that appears to be the chip changing frequency. It immediately reverts back to the crappy
            > 40MHz signal as soon as I stop turning the mouse wheel. Any suggestions before I turn on the heat gun for a chip removal? Thank
            > you very much for any help/suggestions. Additionally, if I need to procure a new Si570 chip, where is the best place to get one?

            If the Si570 is not receiving any good I2C signals it will start at 56.32MHz.
            If it is controlled, 28.2. And the Test tab of CFGSR should be filled with data.

            Assuming your scope checks are good then maybe your Si570 has a similar fault as has been reported before.

            Tony usually offers to replace any faulty parts. Spare ones may be obtained here http://km5h.softrockradio.org/

            73 Alan G4ZFQ
          • Tavi
            OK, this issue is resolved and you guys were right, it WAS a soldering issue. I was positive I had a clean install! If you look at the Si570 chip you will
            Message 5 of 6 , Feb 25, 2013
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              OK, this issue is resolved and you guys were right, it WAS a soldering issue. I was "positive" I had a clean install! If you look at the Si570 chip you will notice that on each side of pins 7 and 8 there are tiny exposed "pins". Inspection under a microscope revealed a tiny splash of solder bridging between one of those "pins" and the top of the case. I don't know where those pins go but apparently they aren't ground! I checked the data sheet and nothing is mentioned of these "little" pins on each side of 7 & 8. Anyway so much for my induction into soldering really little things! As the most challenging part is behind me, I'm hoping the rest of the build is free of issues. The rest of the flat packs should seem enormous by comparison! Thanks to all for your patient responses.
            • Alan
              ... Subject: [softrock40] Re: Ensemble RX II another newbie Si570 chip question... ... These pins were added a few years ago, possibly for factory test/setup
              Message 6 of 6 , Feb 26, 2013
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                ----- Original Message -----
                Subject: [softrock40] Re: Ensemble RX II another newbie Si570 chip question...


                > OK, this issue is resolved and you guys were right, it WAS a soldering issue. I was "positive" I had a clean install! If you look
                > at the Si570 chip you will notice that on each side of pins 7 and 8 there are tiny exposed "pins". Inspection under a microscope
                > revealed a tiny splash of solder bridging between one of those "pins" and the top of the case. I don't know where those pins go
                > but apparently they aren't ground! I checked the data sheet and nothing is mentioned of these "little" pins on each side of 7 & 8.


                These "pins" were added a few years ago, possibly for factory test/setup purposes. No, no mention in documentation.

                So, bad soldering actually caused wrong frequency and bad output waveform?
                If that is true then maybe this has happened before. Others have reported similar symptoms.

                I had a defective Si570 some time ago. After I removed it I connected it "dead bug" style to make sure it really was dead.

                73 Alan G4ZFQ
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