F C Heayberd Battery Charger - UK Vintage Radio Repair and Restoration Discussion Forum

The Philpott · 16th Apr 2017, 6:03 pm

Just got one of these (early 1950's ?) battery chargers with 2v/6v and 12v taps, a sizeable Automat rectifier and an even more sizeable transformer. I really wasn't expecting it to be serviceable and had it in mind to equip it newer components as necessary, but having started with 14v AC from a wall wart a trickle of DC came out the other end, so having done some continuity checks i plugged it into an RCD and got 18v o/c on the highest tapping, which when put to use managed to pump 1.5A into a (loose) car battery.

The transformer is virtually silent, presumably due to good damping/mounting, and we took the opportunity to 'scope the output, which was a good clean full wave DC. Given a modern mains cable and replacement of some of the heat resistant sheaths inside it seems it will be fine for use, but I just thought to query the following:

--Is 18v reasonable as an o/c voltage on the 12v output?

--The current regulator is a bobbin shaped super-coiled heater, with a layer of asbestos underneath the coil. Is there any recommended goo or solution to provide some medium-term stability to the asbestos which won't oxidise and create a stink when I switch it on? If it wasn't for the heating aspect I would use PVA without hesitation- but I don't know if it can 'take the heat'

Thanks

McMurdo · 16th Apr 2017, 6:38 pm

I'd have thought 18V is ok. It might confuse your meter if it isn't a true rms meter anyway as it isn't pure dc. I'd say the asbestos would be ok if you leave it alone. It's heat resisting properties are why it's there.

The Philpott · 16th Apr 2017, 6:53 pm

Good point, the output isn't smoothed and the meter was a similar age to the battery charger, so may just have been measuring the peaks.

16th Apr 2017, 6:03 pm	#1
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,106	F C Heayberd Battery Charger Just got one of these (early 1950's ?) battery chargers with 2v/6v and 12v taps, a sizeable Automat rectifier and an even more sizeable transformer. I really wasn't expecting it to be serviceable and had it in mind to equip it newer components as necessary, but having started with 14v AC from a wall wart a trickle of DC came out the other end, so having done some continuity checks i plugged it into an RCD and got 18v o/c on the highest tapping, which when put to use managed to pump 1.5A into a (loose) car battery. The transformer is virtually silent, presumably due to good damping/mounting, and we took the opportunity to 'scope the output, which was a good clean full wave DC. Given a modern mains cable and replacement of some of the heat resistant sheaths inside it seems it will be fine for use, but I just thought to query the following: --Is 18v reasonable as an o/c voltage on the 12v output? --The current regulator is a bobbin shaped super-coiled heater, with a layer of asbestos underneath the coil. Is there any recommended goo or solution to provide some medium-term stability to the asbestos which won't oxidise and create a stink when I switch it on? If it wasn't for the heating aspect I would use PVA without hesitation- but I don't know if it can 'take the heat' Thanks

16th Apr 2017, 6:38 pm	#2
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,270	Re: F C Heayberd Battery Charger I'd have thought 18V is ok. It might confuse your meter if it isn't a true rms meter anyway as it isn't pure dc. I'd say the asbestos would be ok if you leave it alone. It's heat resisting properties are why it's there. __________________ Kevin

16th Apr 2017, 6:53 pm	#3
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,106	Re: F C Heayberd Battery Charger Good point, the output isn't smoothed and the meter was a similar age to the battery charger, so may just have been measuring the peaks.