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I need a relay HJR-3FF-S-Z 24v coil

Discussion in 'General Electronics Discussion' started by kpatz, Jul 16, 2020.

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  1. kpatz

    kpatz

    329
    88
    Feb 24, 2014
    Hey folks. Another one of my recently broken items is my Staples shredder, which has stopped working in the forward direction. I've done my troubleshooting and determined the cause to be a faulty relay. The relay is a Tianbo HJR-3FF-S-Z sealed 24V coil SPDT relay with 10A contacts. Datasheet is here: https://datasheetspdf.com/pdf-file/657851/TIANBOGANGLIANELECTRONICS/HJR-3FF-S-Z/1

    I checked Mouser and Digikey and neither carry this specific relay. Looking at other relays with the same specs, they appear to have different dimensions/pin spacing, of course. The relay is soldered to a PCB so substituting another kind isn't simple (without hacking anyway). I did find these relays on eBay but all are coming from China or Hong Kong and with all the COVID stuff going on I've seen shipping delays and no-shows from China lately, and I'd like to get my shredder working in less than 6 months. I also checked Amazon and a couple sellers have them (at inflated prices) but the delivery dates are indicative of coming from China as well.

    I suppose in a pinch I could unsolder both relays (there are 2, one for forward and one for reverse) and swap them, so the forward direction works but not reverse. I may do that this weekend, then I can wait months for a China delivery.

    Any other suggestions?
     
  2. Minder

    Minder

    3,178
    689
    Apr 24, 2015
    First, check the printed circuit to the power pins, often this is where the problem is, if you have established it is the relay, if they have a vent plug on top, remove it after replacing and before putting the unit back in use.
    If it does not have a vent, make one with a small drill, it can often be ionization of the interior causing failure.
    It is either a pip in one corner or half way down one side.
    M.
     
  3. kpatz

    kpatz

    329
    88
    Feb 24, 2014
    The relay isn't clicking, even though I confirmed the coil is receiving 24V DC when I press the forward button. This weekend I'll unsolder it from the PCB and check the coil and contacts for continuity out of circuit.
     
  4. kpatz

    kpatz

    329
    88
    Feb 24, 2014
    Update: I unsoldered the relay and tested it. Coil had resistance, and when I put a 9V battery across it, I could hear the contacts "try" to pull in, so I hit it with a 12V power supply I had, and after a couple hits the contacts started clicking again, and working properly. They must have fused in the N/C position. I then soldered the relay back on the board and the shredder works again!

    I may still order another to have as a spare in case it happens again, but at least I can shred again. :)

    Thanks all for your help.
     
  5. Minder

    Minder

    3,178
    689
    Apr 24, 2015
    Does it have the 'nib' half way down the side?
    It would pay to open the relay as per my other post, to possibly cure that problem.
    They are only there for the duration of the de-fluxing of the board.
    M.
     
  6. kpatz

    kpatz

    329
    88
    Feb 24, 2014
    There was no "nib" that I noticed. The "S" in HJR-3FF-S-Z indicates it's a "sealed" relay, and there were no holes, nibs, or even a seam to crack it open without breaking it.

    I think the contacts just welded over time and got stuck. It's working again for now, if it fails again I'll replace it. It's probably a classic case of an under-rated part to boost profit. There's a 100 ohm* resistor on the board that looks like it got too hot too, though I'm not sure why since I only measured 8V across it, and if my math is correct that would be (8/100) = 80 mA * 8V = 0.64 watts. Not sure what the wattage of the resistor is but it looked bigger than a 1/2 watt. Maybe I'll swap a 2 watt part in if or when I have to open the shredder up again.

    The shredder is maybe 10 years old? I don't remember when I bought it, but I only use it occasionally, and I unplug it when not using it.

    * I measured 100 ohms with a multimeter, the resistor is blackened to the point where the color bands aren't readable.
     
    Last edited: Jul 18, 2020
  7. narkeleptk

    narkeleptk

    54
    17
    Oct 3, 2019
    If needed later on,its very easy to take a razor and cut around the bottom (just a hair up from bottom edge) to remove the casing.
     
  8. Minder

    Minder

    3,178
    689
    Apr 24, 2015
    The usual reason for a sealed relay is if it is working in a harsh environment where contamination can occur, not really needed in this application.
    They all come sealed, mainly for the production de-fluxing stage, but those that can be opened, have the pip, but in many cases they are never opened.
    All you need is a small hole through the top of the case to mimic the removable pip.
    M.
     
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