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Old 21st Oct 2019, 5:02 pm   #34
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: DIY battery eliminator for valve radio

Thanks gents for the insight.

I am copying the B+ schematic of the Tubesandmore kit because it has a negative feedback regulation and it is simple. With the filament A supply , the cheapo chinese LT1083 £4 kit is a no brainer, it is cheaper than buying all heatsink components etc separately and it can handle up to max 7.5A:

https://xtronic.org/circuit/circuit-...lators-lt1083/

It has two In4004 diodes doing excatly what you described during connecting and disconnecting the suppy.

I would use a 125mA fast fuse for the B+ output and 1A anti-surge slow fuse for the HT transformer primary. I could connect a properly rate NTC thermistor in the series with the primary of the transformer to tame the initial capacitor charging in-rush current when it is plugged in but i dont think it is necessary in this case.

Then i can get two cheapo analogue voltage meters as panel display.

with the box, i can either get a cheapo wooden box of varying sizes from the local art shop. In the past, i use transparent air tight plastic storage containers. they are cheap, strong and very easy to drill air vent holes. My isolation transformer was housed in such box with cable ties + cable gland compression junction nuts. They are transparent so any smoking component can be seen from outside.

Last edited by regenfreak; 21st Oct 2019 at 5:16 pm.
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