We can only guess at what was connected to the 'return' side of the secondary of the transformer, as you suggest though, some sort of connection to that old 3 pin connector seems likely. Slightly odd that the inner and outer of the Belling-Lee front panel connector are both at high voltage ! Interesting box anyway.
How did you get your BM869s backlight to stay on so long? Mine shuts off so quickly, by the time I get my leads on the DOT the LED goes out and I can't read the meter ; )
Very interesting video! Thanks for sharing. Quite an unusual instrument. How can the current flow back to the winding if the secondary is not connected on one side? Could this be through the transformer capacitive coupling to the primary? It feels like some sort of RF application. Also it seems unisual that an RF antenna connector had been used for a non RF application, especially if the box was manufactured by professionals.
Thanks, I think the return was somehow through the 3-pin connector at the back, but what exactly what was connected there we'll never know. While the connector at the front is indeed often used for antennas, I think they just used that for convenience
It looks like the casing is also self-made, pretty simple but really nice concept, just bended sheet metal. It definitely looks like from some kind of educational institution, but then the antenna plug doesn't make any sense, I don't think that any teacher or docent would allow that for high voltage. I'm not sure why but my first thought was some kind of very basic descaling device, maybe for experimental uses to show the principle or something.
Don't forget that there was a 1 Meg resistor in series, so the current at the "antenna" socket is not much. But you are right, I would never have selected such a connector even with the resistor
@@TheHWcave Basically you only paid for the transformer and all the rest was for free i guess 😁but even if it was only for the transformer it would still be nice deal. If i'm not mistaken that kind of lamination core is used due to low leakage/capacitive coupling between windings, nowadays is more rare to see that configuration but they still exist.
good video
👍
We can only guess at what was connected to the 'return' side of the secondary of the transformer,
as you suggest though, some sort of connection to that old 3 pin connector seems likely.
Slightly odd that the inner and outer of the Belling-Lee front panel connector are both at high voltage ! Interesting box anyway.
How did you get your BM869s backlight to stay on so long? Mine shuts off so quickly, by the time I get my leads on the DOT the LED goes out and I can't read the meter ; )
Per chance, my 869s already had the 256s (4 min 16 sec) back-light time. It's firmware revision PA
Very interesting video! Thanks for sharing. Quite an unusual instrument. How can the current flow back to the winding if the secondary is not connected on one side? Could this be through the transformer capacitive coupling to the primary? It feels like some sort of RF application. Also it seems unisual that an RF antenna connector had been used for a non RF application, especially if the box was manufactured by professionals.
Thanks, I think the return was somehow through the 3-pin connector at the back, but what exactly what was connected there we'll never know. While the connector at the front is indeed often used for antennas, I think they just used that for convenience
@@TheHWcave Makes sense, thanks. Quite nice to see these old devices. Thanks
It looks like the casing is also self-made, pretty simple but really nice concept, just bended sheet metal. It definitely looks like from some kind of educational institution, but then the antenna plug doesn't make any sense, I don't think that any teacher or docent would allow that for high voltage. I'm not sure why but my first thought was some kind of very basic descaling device, maybe for experimental uses to show the principle or something.
Don't forget that there was a 1 Meg resistor in series, so the current at the "antenna" socket is not much. But you are right, I would never have selected such a connector even with the resistor
Nice finding! Can i know approximately how much had you paid for it?
Thanks. £14 including shipping.
@@TheHWcave Basically you only paid for the transformer and all the rest was for free i guess 😁but even if it was only for the transformer it would still be nice deal. If i'm not mistaken that kind of lamination core is used due to low leakage/capacitive coupling between windings, nowadays is more rare to see that configuration but they still exist.