Question APC CS-350 & CORSAIR RM850x are they compatible? Short circuiting.

Mar 10, 2019
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Hi recently got a brand new PC: i9 9700k, AORUS ULTRA z390, 16GM RAM and no GPU yet.

I took out my good old APC CS-350 backups ( https://www.amazon.com/APC-BK350EI-Back-UPS-Discontinued-Manufacturer/dp/B00006BBIK ) I used in 2002-2007 with my old PC. I removed its old battery and bought a new one from a trusted shop, a battery made in germany or by a german company. I tested the UPS with an older computer (psu 450w) and its monitor at my job and it worked flawlessly.

Then I came home and decided to hook it up to my new PC. I have first of all switched off the switch on the PSU to cut its power. Then I plugged in the monitor and PC to the back ups. I put backups' plug into wall socket, then I switched on the switch on the PSU and I began hearing crackling noises from the PSU, I switched it off waited a few second and switched it on back again and crackling noises went at it again. I got scared a bit. Plugged everything out and smelled the PSU vents and there was indeed some very weird smell.

I then plugged my PC regularly into the wall socket without a UPS - it worked nicely as if nothing happened. But when the PC is plugged in but not yet turned on I hear a coil whine like this:
View: https://www.youtube.com/watch?v=A_vXA058EDY


And sometimes at the moment when I press the turn on button I hear a click from the PSU when the computer starts.

Why did this happen? Is the UPS not strong enough? Was the PSU defective? I'm affraid to use that UPS again with my new pc.
 

InvalidError

Titan
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Many PSUs have relays to bypass inrush current limiting components after the PSU has turned on, that's probably what you heard click.

The crackling and burning smell are definitely not normal. I'd hazard a guess that a high voltage component on the primary side has a cold solder joint that is arcing over - I repaired a TV about three months ago with this sort of issue.
 
Mar 10, 2019
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Thank you. I have indeed studied english language at university but I failed to understand the meaning of your words. Help me out here.

Many PSUs have relays to bypass inrush current limiting components after the PSU has turned on, that's probably what you heard click.
so hearing click when you turn on the computer no matter if PSU is brand new or used is normal?

The crackling and burning smell are definitely not normal. I'd hazard a guess that a high voltage component on the primary side has a cold solder joint that is arcing over - I repaired a TV about three months ago with this sort of issue.
I'll just bring the computer to warranty. Meanwhile the important question is if a APC CS350 UPS is compatible with a PC that has a 850 PSU? I wonder if the same will happen if I get my PSU replaced? I hook it up and it starts frying again...
 

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Titan
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so hearing click when you turn on the computer no matter if PSU is brand new or used is normal?
If the PSU has a bypass relay in it, yes, relays click whenever they change state. PSUs which have such relays may turn them on and off whenever the PC turns on and off or only when AC power gets applied and removed.

Meanwhile the important question is if a APC CS350 UPS is compatible with a PC that has a 850 PSU? I wonder if the same will happen if I get my PSU replaced? I hook it up and it starts frying again...
When AC power is available, power passes straight through the UPS, the UPS does nothing beyond minimalist surge suppression. Depending on what sort of hardware you have in your system, 350VA (~200W) might be very close and running such a small UPS' tiny battery this hard won't give you much usable backup time and will ruin the battery very quickly if you need backup power on a somewhat regular basis. I personally wouldn't use anything less than an UPS with 24V battery for my main PC, which typically means at least 1000VA.
 
Mar 10, 2019
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Well the PC parts are these:
  • i7 9700k CPU
  • Gigabyte Z390 AORUS ULTRA, 4xDDR4 4400, PCI-E 3.0 x16, HDMI, USB-C
  • FRACTAL DESIGN Define R6 Black USB-C
  • CORSAIR PSU RM850X 750W GOLD
  • Cooler Noctua NH-D15
  • 1 SSD and 3 HDDs inside
  • DDR4 Corsair Vengeance LPX Black 16GB (2x8GB) 3000MHz CL15 1.35V RAM
  • NO GPU.
I'd love the UPS to at least give me 1 minute in case of electricity disappearing to save my work and shut down the PC as well as quick surges that happen. You think the APC CS 350 I have should be enough for that?
 

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Titan
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I'd love the UPS to at least give me 1 minute in case of electricity disappearing to save my work and shut down the PC as well as quick surges that happen. You think the APC CS 350 I have should be enough for that?
The CPU including VRM losses can add up to more than 100W on its own, then you have 20-30W for everything else on the motherboard including RAM, 30-50W for HDDs, SSDs, fans, etc., 20-50W for the monitor, a couple more watts for external devices like mouse, keyboard, USB hubs and whatever else you may have, etc. You may already be close to the UPS' limit even without a GPU. Should a power outage occur while your system is under heavy load, the UPS may shut down prematurely from overload or the battery voltage dropping too low too quickly.
 
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Mar 10, 2019
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so if my PC lets say uses nearly 350 VA and APC is 350VA then in the moment of power outage it may only last for a very very short time? Upgrading to a APC CS-650 with 650VA should leave me hassle free then?
 

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Titan
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so if my PC lets say uses nearly 350 VA and APC is 350VA then in the moment of power outage it may only last for a very very short time?
A 'very short time' as in it may immediately shut off. Some UPS allow a few seconds of overload, others outright cut off. 650VA would be good enough for your system as-is but will be potentially borderline if you add a 150+W GPU later.
 
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