How to check if your relay box is properly isolating your autoguider

Discussion in 'Legacy Models - Community Support' started by CrossoverManiac, May 22, 2023.

  1. CrossoverManiac

    CrossoverManiac Standard User

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    The last time I used the ST-4 for autoguiding, I burned out the motherboard of my mount. The thing is, I don't remember if I was everything through the relay box or not as I was switching back and forth between the relay box and directly hooking up the "flipped" RJ12 cable and running everything though the relay. To avoid another burnout, I have been using an off-axis guider but I do want to go back to using the guide chip as before. How do I check if there is any issues with the relay box and is there anyone who could fix it?
     
    CrossoverManiac, May 22, 2023
    #1
  2. Colin Haig

    Colin Haig Staff Member

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    That sounds like you did something fundamentally wrong. What mount is it?

    Modern cameras are usually opto-isolated, and the power/ground on the camera is separate from the guider output port that goes to the mount.
    Old beasts like the ST-4 required a relay box for most mounts.

    You need to find the correct wiring for the mount guider input port (Usually there are 5 pins - a common pin and 4 directions).
    Some mounts put +5 or +12V on the 6th pin. If shorted, that can damage the mount.

    You also need the correct wiring between the mount and guider.

    We can't repair these things any more. Too old, no part available.
     
    Colin Haig, May 23, 2023
    #2
  3. CrossoverManiac

    CrossoverManiac Standard User

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    The mount is the SkyWatcher EQ6-R Pro. The camera is either the SBIG ST8 (which I use for photometry) or the ST2000XCM (for astrophotography). I am not sure since I was switching between them on that night when my mount's motherboard. Now here's the thing: I have used the ST-4 on the ST2000 and even used it to take a single 20-minute image of two different targets. Before, I thought it was something wrong with the camera and now I am wondering if the relay caused it. Also, someone warned me that plugging the relay into the "IC2 AUX" port and then plugging in the ST-4 would damage my mount. I don't remember which outlet I used (the other is the "AO7 CFW8 SCOPE" port). So , could either a defective relay or plugging in the relay into the wrong outlet be the cause. Also, I know that you don't service the relays but what about the old ST cameras?
     
    CrossoverManiac, May 23, 2023
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  4. Colin Haig

    Colin Haig Staff Member

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    You have to be very careful with this, especially when running everything off separate power supplies. The ground connection on the TIC guider jack will connect digital ground of the camera to the digital ground of the mount.

    The AO/CFW/SCOPE port is the one that goes to the 3-port expander or TIC cable for guiding, and is normally used for CFW-8A, AO-7, and the connection to the guide input of the scope.

    Correct - DO NOT PLUG INTO the I2C Auxiliary port. It has +12V, +5, +3.3V on it, and will blow up anything that is not an SBIG device.
    It is NOT for use with guiding. It is only for use with certain accessories.
    It has a different gender (male) so it should not be possible to plug the TIC adapter into it by accident.

    The manuals are here:
    https://diffractionlimited.com/legacy-product-support/

    The ST-series cameras are now over 20 years old, and did not have opto-isolators in them. We cannot repair them anymore as parts are no longer available.

     
    Colin Haig, May 23, 2023
    #4
  5. Mike Hambrick

    Mike Hambrick Cyanogen Customer

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    I have a lot of old files related to the relay adapter box that I got from Tim Puckett in the pre-Diffraction Limited days. I have attached a couple that may be of interest to you. I am not sure that you will find either of these in the Diffraction Ltd. archives.

    I went through a long process trying to get a STi camera with opto-isolated relays to work as a guide camera with my old Astro-Physics 800 mount, but I was never successful in doing so. The older model cameras (e.g. ST2000) with electromechanical relays worked great, but not the STi

    The attached documents are not all of what I have. Let me know if you want me to send more.

    Mike
     

    Attached Files:

    Mike Hambrick, May 23, 2023
    #5
  6. Colin Haig

    Colin Haig Staff Member

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    Mike - thanks for posting those.
    The ST-I should work fine with A-P mounts - usually if it doesn't you've got the wrong cable wiring between ST-I and A-P mount.
     
    Colin Haig, May 24, 2023
    #6
  7. Mike Hambrick

    Mike Hambrick Cyanogen Customer

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    Hi Colin

    The STi works just fine with the newer A-P mounts, but we were never able to get it to work with the old 800 mount. I also had no problems using a ST2000-XM for guiding the 800 mount as long as I was running it with a relay adapter box, but we (Tim Puckett, George Whitney and I) finally concluded that it was the opto-isolated relays in the STi that could not be made to work with the electromechanical relays in the 800 mount.

    For a long time, we thought that the problem was because there is not a 12V DC in the output cable from the STi to the mount, but after trying several different schemes for adding the 12V DC without success, we gave up. I finally resolved the problem by upgrading to a new mount.

    Mike
     
    Mike Hambrick, May 24, 2023
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