Hello,

I now have in my possession, two battery-powered valve radios, which first need to be repaired/refurbished and proven operational.

I have searched and found a few suppliers of circuit boards that once assembled will provide the various voltages, but I have been thinking of making up a box that will contain Li-Ion batteries powering two DC-DC converters.

One will perform in boost mode and provide the HT and the other will perform in the buck mode to provide the heater power.

Can anyone see any issues with this method?

Regards

Lloyd

Hi Lloyd

Have a look at this https://www.siliconchip.com.au/Issue/2020/December/Power+Supply+for+Battery-Powered+Vintage+Radios

It should do what you want.

Yes, I have built 2 of the Silicon Chip types utilising 4x 18650 batteries. 2x for HT & 2x for filament supply. The units work very well with low noise and low battery cut out. They won't work with 9V filament supply requirements though. They are also compact enough to be housed in a box with the batteries contained and fitted into portable radios .I plan on building more when time permits.

I have not really resorted to using battery based PSU's for oldies only a single voltage "No Break" for a scanner. Switch mode can be an issue with valve stuff.

I did build one a while back for 45V and 135V and 5V for 3 UX-201A's, One secondary was dedicated to the 5V filaments and a CPU fan to help a Heatsinked 7805 keep its cool. The other a 7905 for bias. Do be warned that both 5V regulators need a 1K load resistor. Step up from that winding was a reversed (salvage) transformer.

45V from an LR8; 135V from a second LR8. From the same "B" rail.

That was another plug in job so it could be used on other sets, in the guys collection.

Those little CPU fans can be quite handy for venting PSU boxes & other things.

Thank you all for your comments.

Yes, I am aware of the SC board and have one, I am still to source the parts and build it.

I guess I was just trying to shortcut the process, but as you mention, switch-mode power supplies can introduce their own issues.

Looks like I better order those parts.

Thanks again.

Just as a matter of interest, I have a Philips battery radio that was repaired some months ago and then powered by a lash up of ten normal el cheapo 9 volt batteries and a couple of one and a half volt D cells.
Unit has been running for weeks at several hours per day in the work shop.
I feel for these restorations a built up battery box is a good answer.
Then, when later stored and batteries removed no real financial load is part of the radio. Just a neat battery box.
JJ

I feel your pain Lloydc, with sourcing the parts. With the interruption to global supply chains at the moment, it took me 3 months to source all the parts for this project from 4 suppliers. It's well worth it though as it does work well. The inverter switching is done at a low frequency so interferance is minimal. It's a shame these can't be bought as a complete kit with parts included. There's a lot of projects that SC design that I don't bother with because of the effort required to source all the bobs and pieces.

Once upon a time, some of the parts purveyors actually offered complete kits for you to assemble. DS Frequency counter is one of them.

MBVC

Photos uploaded to Post 7.

SC on-line shop now sells complete kits.

To 'Lloyd C' , Post #5, saying......
I guess I was just trying to shortcut the process, but as you mention, switch-mode power supplies can introduce their own issues

Yes, I'm building the same thing now. Quite a few old experienced guys on Youtube do warn against using and 'Switch Mode' gear with old radios, due to the interference/noise they can introduce!

A classic here was a FAX using the House / Office, workshop phone line as an antenna & Its PSU getting into a 175kHz IF.

Marc