[ARC5] running ARC-5 receiever fillaments on AC.
Brian
brianclarke01 at optusnet.com.au
Sat Aug 26 22:04:26 EDT 2017
Using a 24 Vac transformer is a very poor idea. You need to ensure that the regulator under full load does not see dips in the rectified DC from the raw rectified AC. You also need to allow for AC mains droops; the electricity supply authorities are permitted 10% droop in mains supply. Suggest at least 34 Vac nominal.
Here’s the maths on your suggestion:
24 Vac rectified –> very rough 33.94 Vdc peak, less 10% supply droop –> 30.54 V peak, less two diode drops (FWB) at full load –> 29.14 V peak value. The average will be less. Doesn’t leave any headroom for the 7824. You can do the maths on 34 Vac.
You’ll find the same design ‘philosophy’ used in very good quality telephone exchange battery supply and back-up systems. Where this design philosophy is ignored, eg, the exchange is run by an accountant, you will hear hum in telephone handset earpieces throughout the whole exchange area.
And just a little point – no ARC-5, ATA, ARA, SCR-274N equipment uses tubes with filaments – all their tubes have HEATERS.
73 de Brian, VK2GCE.
On Sunday, August 27, 2017 11:29 AM, you said:
<snip>
I'm going to rectify the 24VAC to 33.6 VDC and pass that through a LM7824 to get back to 24V.
That should keep the oscillators happy!
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