Big Bang (not just a Theory)

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Terry Smedley

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Sep 12, 2022, 3:17:14 AMSep 12
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This woke up the house.

Thinking to replace it with a Nichicon LNR1H104MSE (100000uf @ 50v), similar form factor.

tas


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rand...@hotmail.com

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Sep 12, 2022, 8:42:43 AMSep 12
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Was it sitting for a few years unused?

Always best to wake-up slowly with a variac ;-)


Randy

Joseph E McGlone

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Sep 12, 2022, 8:57:09 AMSep 12
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Tas

 

I have not tried it but, I was wondering if a capacitance multiplier circuit could be used in place of the enormous H8 power supply capacitor?  Here’s a link to the concept:

 

https://resources.pcb.cadence.com/blog/2019-designing-a-capacitance-multiplier-as-a-power-supply-filter

 

Joe

 

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rand...@hotmail.com

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Sep 12, 2022, 9:08:37 AMSep 12
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I would say it's a bad idea. The issue would be the current,  these old machines use a lot of power via linear power supplies. This power is best tamed with brute force. Finding a semiconductor to handle the current would be hard. 

That said the capacitor will be expensive. 


Randy

Glenn Roberts

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Sep 12, 2022, 9:21:29 AMSep 12
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Wow. That’s the first one of those I’ve seen fail. Any collateral damage? Does serve as a reminder not to leave an original H8 system running unattended… good luck!

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On Sep 12, 2022, at 7:08 AM, rand...@hotmail.com wrote:

I would say it's a bad idea. The issue would be the current,  these old machines use a lot of power via linear power supplies. This power is best tamed with brute force. Finding a semiconductor to handle the current would be hard. 

rand...@hotmail.com

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Sep 12, 2022, 9:30:16 AMSep 12
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Actually they mainly fail after sitting for years unused. If old equipment with linear power supplies is being brought up its best to current limit it. A variac is best but you can use a couple of 100 watt incandescent lights in series. 

Yes it can be very dangerous to people and equipment. 


Randy

rand...@hotmail.com

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Sep 12, 2022, 11:36:19 AMSep 12
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When large electrolytic caps sit for extended periods condensation can build up inside and the dielectric can get misformed when you plug it in steam can cause a violent explosion. Slowly charging them dissipates the moisture and reforms the cap. It should be slowly brought up over at least 48 hours. 


Randy 

Mark Garlanger

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Sep 13, 2022, 1:19:16 AMSep 13
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I really need to get a variac. There are so many options on amazon...

ocl...@earthlink.net

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Sep 13, 2022, 9:30:34 AMSep 13
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It seems the ones for sale on Amazon are almost all the generic Chinese ‘big reds’, which fall into two versions, the 1000VA model with analog meter and one outlet, and the 2000VA model with a digital meter and two outlets. eBay seems to sell mostly the same two, plus lots of vintage ones that are all over the place in their specifications, and not any less expensive than the new ones. You have to be careful with the specifications in the listings, often the sellers don’t know the difference between voltage and power, or write laughably silly things about them.

Lee Hart

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Sep 14, 2022, 3:37:49 PMSep 14
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So, you've discovered Rube Goldberg's alarm clock! :-)

No, I don't think a capacitance multiplier is the right choice for this circuit. A capacitance multiplier does not store energy, so it can't supply power during the AC line zero-crossings. A capacitance multiplier is typically used as the 2nd or 3rd stage of filtering in a low-power circuit where hum must be reduced to an insignificant level (like an audio preamp).

Lee Hart

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