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Old 17th Apr 2024, 3:48 pm   #1
Michael Maurice
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Default Dual capacitors

I am restoring a RGD 1046 radiogram and am replacing the smoothing capacitors.

Because of the way the amplifier chassis is laid out, it is easier to fit two 16+16uF capacitors and leave one terminal floating.

Is it OK to do this or am I best fitting a resistor of say 22K so that the unused section still gets HT. The use of a high value resistor means that it wont affect the maximum capacitance of 16uF after the rectifier.

Any thoughts/
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Old 17th Apr 2024, 4:23 pm   #2
HamishBoxer
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Default Re: Dual capacitors

I cannot see a problem at all. Me, I would leave floating.
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Old 17th Apr 2024, 9:11 pm   #3
kalee20
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Default Re: Dual capacitors

It will be fine!

And... you may be able to use the unused section elsewhere and have better smoothing - you have extra uF's that I'll bet the original Dynatron designers wished they had access to, and didn't!
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Old 18th Apr 2024, 3:29 pm   #4
dave cox
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Default Re: Dual capacitors

I would avoid letting it charge up unless it has a sensible discharge path, i.e. be safe after a few mins.

dc
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Old 18th Apr 2024, 7:56 pm   #5
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Default Re: Dual capacitors

Quote:
Originally Posted by kalee20 View Post
It will be fine!

And... you may be able to use the unused section elsewhere and have better smoothing - you have extra uF's that I'll bet the original Dynatron designers wished they had access to, and didn't!
Indeed, e.g. a bit of extra filtering for low-level audio stages in conjunction with an appropriate resistor. They rarely take much current and the relatively low signal levels mean that a few lost HT volts shouldn't be a problem. Though it has to be said that once supply ripple has been reduced to a point, other sources of hum such as poor layout or unwise commoning paths can become significant....
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Old 18th Apr 2024, 8:17 pm   #6
G6Tanuki
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Default Re: Dual capacitors

I would strap the unused section to earth. "Floating" capacitors can do some 'interesting' things and acquire enough charge to bite you under a range of unpredictable circumstances.

[I have been bitten by a capacitor that's spent at least a year sitting quietly alone and unloved on a shelf]

Grounding unused sections minimises this risk.
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Old 18th Apr 2024, 11:14 pm   #7
Michael Maurice
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Default Re: Dual capacitors

Thank you all for your input, What I’ll do is strap the unused sections to ground via a 1K resistor.
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