Agree Jacques, I did some poking around as well and found what you described.
Thanks,?
Tom
On Friday, February 21, 2025 at 10:23:02 AM EST, Jacques Fortin <jacques.f@...> wrote:
Hello Tom,
I believe that the ¡°bubbles¡± in the original choke encapsulation just came from when the coal tar was poured in during manufacture.
There is no possibility that the part ¡°overheated¡± IMHO.
For the suitability of the replacements: as the 4Hy choke from the R-390A Audio Deck you used only have 110 ohms of internal resistance, it will be 100% OK to add a 110 ohms resistor in series with it to ¡°emulate¡± the 220 ohms of the original part.
I also checked if any recent manufacture Hammond choke can be used, but no luck there: the smallest 4Hy one have a 300 ohms internal resistance, and that value cannot be ¡°reduced¡± in any way.
The other 4Hy parts are really too big for the task, not speaking of the cost¡
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73, Jacques, VE2JFE in Montreal
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Hi Jim,?
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Well that's not what I wanted to hear, but I understand. I'm actively looking for a suitable replacement choke. The on I substituted in was all I had laying around and figured it would be good for a test.
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The original choke is encapsulated and the bottom side shows bubbles in that encapsulation. I have designed products that have used encapsulation in the past and have seen these bubbles before, they are usually caused by the part overheating.
