I have a beautiful American Bosch model 5A that requires a earth connection and of cause the step-down transformer doesn't provide earth.
I do have a device that I made a few years back that reduces interference via 3x .01 safety caps which basically is a simple power board which I plug the step-down transformer into.
Is there any reason why I cant tap the earth off that and provide a seperate connection to provide earth to this set. Its the most convenient as running a seperate earthwire in my house will be a little messy.
Its not a hot chassis and it does have a earth terminal.

Gday Carl, did u get ur earth connection sorted?

5A is a transformer set. One may need to put the step down transformer in a box. Beware, some of those step down transformers are not isolation transformers, they are Auto transformers primary & secondary are common to mains.

There is one of those here and the Variac tm / Dimmerstat (slide transformers) are also Auto transformers providing no isolation from mains. The metal body of all here are grounded.

C20 in the 5A, which should be a line cap; I often see on Neutral as they are not a filter but the RF ground return via neutral for a non grounded set. One of step down transformers here has a special adapter NEMA 2pin to NEMA 3pin with a terminal to attach an earth to the grounded transformer frame.

To avoid accidents all 110V / 115V step down units have NEMA sockets and the units, NEMA plug tops. The shortage of those is a safety risk as I have seen a few 110V sets and actually a 32V set, with 240V Plug tops: That's asking for trouble.

NB. A 30mA RCD on the primary may not trip below 130V. That can be tested for by a device.

DDDazzler I believe I have the solution but havent worked out how I can add a few more hours in the day in which to do it lol.

As noted: The only issue I have is related to getting proper NEMA plugs & sockets: It is as far as I am concerned intrinsically dangerous to man & machine to use inappropriate plugs and sockets for the operating voltage of the device. I have a set clearly marked 110V that came with a 240V Australian plug & related damage because of it.

Isolation transformer here is commercial cast off from lighting (3A). Its in an nice metal box. As noted it has had mods, one being the addition of a big red manual reset "Kill Switch".

Marc

I once did a repair to a "Rincar" radio that was a classic AA5 series heater design.
It looked like it had come from Hong Kong as it was a 240 volt radio that used an autotransformer, It had a 3 pin mains plug and the chassis was grounded, with no internal connection (save via a capacitor) of the mains to the chassis. Scary to work on!

The autotransformer was cooked, the original half-wave rectifier toob was gassy and I didn't have either.

What I did have was a Jaycar or Altronics transformer with a tapped 48 volt secondary that was bigger that the original tranny but could fit when the rectifier was removed.

A bit of rearrangement of the heaters and a full wave voltage doubler using 1N4004s turned it into a safe, fully grounded chassis radio that ran cooler than before.

Unfortunately, neither Jaycar nor Altronics now seem to stock this transformer. Not in E-I construction anyway.

I have a Westinghouse 6 tube "AA5" radio that has a step up transformer to go from 120V to 240V to provide higher B+ for the audio output stage. The output tube is a 50L6, which can make use of this higher B+. If this radio found itself in Australia, one could (assuming the 60Hz transformer could work at 50Hz) rewire this set to accept the 240V to the rectifier tube, and the transformer would provide the 120V for the heater string.

I'd assume that you'd simply switch the "Mains voltage select" to the 230 position, and it would work here.

Live chassis of course, so keep fingers away from the metal parts.

Whilst not original as a hacker beat me to it. Collector brought me this particularly dangerous almost AA5 style set, to make it safer. There was a small added transformer but only useful for removal.

The wash up of that mess was a stand alone PSU, with the heaters re-wired parallel. Cable was fitted with a tube base and PSU with Octal base.

Pin one common ground, 2&7 Heaters (7 common to ground) pin3 B+).

Worked quite well & no chance of getting zapped by touching a chassis.

All situations assessed on the what if basis?

Modifications can have ramifications.


Marc