Hello,
New to vacuum valve radios but have always been fascinated by them. I have been getting up to speed with basic electronics and would like to know if anybody has come across a dim bulb current limiter here in Australia?
Thanks
Bill

A piece of home made test equipment.
A 230 volt incandecent light globe connected in series with radio being looked at.
An essential bit of equipment for all valve radio, television and in fact lots of other repairs.
I have found a 75 watt globe ideal for most radios, and have two in parallel for television work.
Mount 230 volt globe sockets on a board with a bypass switch.
In conjunction with an isolation transformer gives the most ideal service platform.
Although some repairers use variac's. I have one but generally don't use it as it gives no current limiting.
JJ

Hello JJ,

Thanks for your post. In your last line you state that it gives no current limiting? Is that with the variac in place? I have put one together and had followed a Youtube clip on the subject and the presenter drew up a circuit diagram and then modified it to include a LED in place to indicate when the bypass was used. With subsequent testing with my colleague (qualified electrician) we have found problems implementing this LED bypass lighting up? Have you by chance seen this video on Youtube https://youtu.be/T2UNVoT4gCI

Thanks

Bill

Member Dave Tipton (Tippy) has covered this topic well here: https://www.youtube.com/watch?v=ykUlzhCTLvg

A variac gives no current limiting, so on its own is useless for this type of work. And no advantage when included.
You will still get smoke and sparks just at a lower voltage, which is entirely opposite to what the dim globe device is supposed to achieve.
So, leave the variac out in this case and use it for other projects.
Just the incandecent globes is really all you need for good safe current limiting.
The isolation transformer is added protection, especially when probing with other test equipment and hot chassis units.
Which I won't touch btw.
Have been in the repair/service industry since the 1960's Full time occupation.
The dim globe is essential for safe repair and is nothing complex or new.
I have found that a very high percentage of internet info, particularly utube info is very technically incorrect.
And a lot done by unqualified people with dangerous practices.
Unfortunately some of these Utubers are very popular. Causing miss information being passed on as gospel.
And entirely different electrical regulations depending on which country, in some cases.
I don't use any other electronics with the bypass switch, no need, on or off ,KISS. Marked with red visual indicator.
JJ

Thanks all I really appreciate the quick response to my query on the dim bulb tester. I have saved Dave Tipton to my favourites on Youtube.
Yes JJ I take on your advice KISS as it can be tricky navigating all the information when you are new to this.
Cheers
Bill

This is how I made my dim bulb tester. Take a 2 metre (or what ever length that you like) extension lead, cut through the outer inulation and expose the active (red or brown) wire. Check with a multimeter that the active wire is connected to the correct pins of the plug and socket of the lead. If OK, wire the red wires to a standard batten light bulb fitting so that the current goes through the bulb filament. Screw the batten fitting to a board.

If you like, also fit an on/off switch in the active line and a bulb bypass switch across the batten switch connections. I have done neither, and if expecting possible trouble, I hold the plug with the radio plugged into it, and quickly unplug if the bulb does not dim quickly. This way both hands are nowhere near your radio for safety.

The dim plug tester is plugged into the socket used for the soldering iron. If the radio is plugged in the soldering iron isn't. That way you can't solder with the radio powered up.

You've always got to be on the ball as to what is powered up and what is not. If you establish this type of discipline and habit you protect yourself from brain fades.