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G6Tanuki · 6th Mar 2019, 4:32 pm

I fear the vibrator-transformer on my R209 has developed a shorted-turn: the radio's drawing something near 3A when it should be half that, the HT is only about 70V (so the voltage-regulator tube doesn't strike) and the transformer gets smellily-hot after about ten minutes. I've changed the various suppression components around the vibrator but that hasn't made any difference.

It's a rather 'hot', well-performing R209 - I recently reworked it replacing all the leaky grey-rubber-covered decoupling capacitors in the plug-in modules [this being one of the best bits of the R209 design - so easy to work on!] and a bunch of resistors that had gone out-of-spec, along with giving it a complete set of NOS made-for-the-US-Military-by-Sylvania-and-Tung-Sol valves and it then performed better than it ever had in the previous 35 years I've owned it.

So to keep it going I plan to convert it to mains-only. My idea is to use a 15V 1.5A transformer feeding a bridge-rect with something like a LM317 to provide the 600ish mA for the heaters, then another small 30V transformer wired 'backwards' across the 12VAC from the first transformer to provide the 100-or-so-Volts of HT.

Just wondering if anyone else has done similar?

6th Mar 2019, 4:32 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	R209Mk.2 PSU I fear the vibrator-transformer on my R209 has developed a shorted-turn: the radio's drawing something near 3A when it should be half that, the HT is only about 70V (so the voltage-regulator tube doesn't strike) and the transformer gets smellily-hot after about ten minutes. I've changed the various suppression components around the vibrator but that hasn't made any difference. It's a rather 'hot', well-performing R209 - I recently reworked it replacing all the leaky grey-rubber-covered decoupling capacitors in the plug-in modules [this being one of the best bits of the R209 design - so easy to work on!] and a bunch of resistors that had gone out-of-spec, along with giving it a complete set of NOS made-for-the-US-Military-by-Sylvania-and-Tung-Sol valves and it then performed better than it ever had in the previous 35 years I've owned it. So to keep it going I plan to convert it to mains-only. My idea is to use a 15V 1.5A transformer feeding a bridge-rect with something like a LM317 to provide the 600ish mA for the heaters, then another small 30V transformer wired 'backwards' across the 12VAC from the first transformer to provide the 100-or-so-Volts of HT. Just wondering if anyone else has done similar?