Old-fashioned hot shoe flash does not fire on my Lumix G7

I have a Lumix G7 camera, and a Hanimex TS755M external flash from a junk shop. When connected to the camera, it doesn’t fire.

  • I have checked the Hanimex flash voltage, both looking it up on http://www.botzilla.com/photo/strobeVolts.html and measuring it myself — it should be safe. (It would be nice if the G7 manual actually listed the voltage limit.)

  • The flash fires fine if I charge it and press the test button, so that bit works.

  • The camera is detecting the presence of the flash, presumably using the READY pin on the hot shoe, so that bit works.

  • If I short the central pin on the flash to the ground connector on the side, it doesn’t flash. Actually, testing this again, this works fine. Apparently I just wasn’t making decent contact before.

Is this pointing to a defunct flash, or is it more likely that there’s a configuration issue on the camera which I’ll need to fix before it’ll operate the external flash (which TBH seems unlikely given that it’s detected)? Alternatively, I haven’t been able to find a manual for the Hanimex flash, so maybe I’m doing something wrong there; but it only has two controls…