A heads-up on this topic:

I asked Rod Champness about his proposed battery eliminator. He replied thus:

"It is actually working and working well. It will power all battery radios in the AORSMs (unless I missed one) and probably most of the pre AORSM battery sets. It will power domestic vibrator sets, but not car radios."

His next step is to get PCB's made, and we'll hear about the product officially in Radio Waves in due course.

UPDATE: I should add that the Champness eliminator is mains powered. There are other designs, such as the Maher eliminator, which are powered by batteries (so they are battery substitution/replacement rather than battery eliminator).

Will look forward to that.
BTW does anyone have a circuit for one, I wouldnt mind trying to build one.

Josh

There are probably numerous such circuits published in EA and RT&H (and possibly SC) over the years. I haven't looked because I'm not into battery radios.

There is an American circuit in one of the links I gave recently in another thread which could be modified for 240v input.

Hi

I have built a couple of these for use with my valve portables and it works very well.

http://www.vintage-radio.com/projects/battery-set-psu.html

As noted above, there are lots of different ones around and this was suited to my radios.

Dan

Thanks Dan I actually came across that one and am intending to build it
Good to know it works well

Josh

I often build to suit the application albeit I have made a couple of more universal ones. Where there are low currents & more voltages, I find LR8 Regulator to be quite handy & have built a PSU with a common "B" voltage around 250V (Reversed transformer) and set LR8's to supply the individual regulated B+ rails. They are then easy to tweak.

Limit is around 15mA 450VDC max input and can be set to go as low as 5V. Good with UX-201-A as they will lock up before the plate current is exceeded. They can be used with TIP50 for higher currents.

Marc

Kevin Maher was selling his "B" battery kits at the RHS event in Canberra a few months back, so a search online might find references to that.

I've built one myself to his recipe from components, but wired point-to-point not on a PCB. DC outputs measured fine using a 9-volt dry cell, but when I connected it to my Hotpoint P573 something went ping - I think I may have blown a valve heater element. In that radio the heaters are in series.

My radio has a complex power switch that includes a "battery save" setting that is supposed to re-charge batteries when operating on mains power. Obviously that has to be disconnected when using a battery eliminator like this one. I might have messed that up somehow and generated a short in the heater circuit somewhere, hence the unwanted ping. But have been distracted by other things for a while so not traced it yet.

Maven

Kevin Maher was selling his "B" battery kits at the RHS event in Canberra a few months back

I think you may mean Tony Maher. If so, then the HRSA has recently notified members that he is seriously ill at the moment.

Sorry - yes I did mean Tony Maher. Sorry also to hear about his health problem - he was in fine form when I saw him, though I know he had been out of commission at various times before that.

The circuits for his designs can be found online. In fact the reason I built mine from scratch was that he was not answering emails at the time when I was trying to get a PCB or kit from him.

The key component is a toroid transformer intended for 120v primary to 6v secondary. Altech stocked it when I last looked. When reversed it generates B+ voltages derived from primary input 6-9vdc. A timer IC and a few transistors, diodes and capacitors do the dc > ac > dc conversions in a very compact unit.

Maven

The circuits for his designs can be found online

There's this one from 2001 for 67.5v/90v/108v HT:

http://www.portabletubes.co.uk/sitefiles/ausbatt.htm

... and he's designed updates since:

https://www.youtube.com/watch?v=jEAeLtBafTM

If you already write for microcontrollers or configure a 555 they can be designed/made from junk
and a centre tapped transformer if you need to push pull for real AC.

The reason I’d go for a digital PWM is because by varying it, the same circuit can light neons,
power motors and ring phones (i.e.. adjust the mean voltage of it’s output, or find the best frequency for any arbitrary transformer).

I think that while PWM makes sense from various points of view, most PWM power supplies are relatively noisy in RFI terms for AM radios, and these battery eliminators have to sit within a centimetre or so of the internal loop antenna. The Maher design, driven by a 555 equivalent, needs sheilding. The toroid transformer seems to help keep down the RFI.

Maven

I have a couple of Tony's eliminators, one 67.5v and one 90v. The RFI isnt really much of an issue, as far as Ive observed, even in the very small portables.
With the mods for autostart etc, it does get a bit messy and could do with a PCB update.

Ben

Does anyone know if the PCB’s for this are still available? Thanks

I have built a couple of the Silicon Chip Battery Powered Supplies that were published in December 2020. They utilise Li-on battery cells with HT to 135V and filament supply 1.2 - 2.5volts. They work quite well with good run time and easy recharge. Terrific for portables and small enough to fit inside also.