Dynamode UPS Buzzing

  Dave-dxer 17:40 27 May 09

Following a recent power cut my Dynamode 850va UPS has begun to buzz intermittently. It does this even when it is not under load, e.g., nothing at all connected to the outputs. It is completely random and after a while it quietens down and stops. This is the older UPS with 2 British 13 amp sockets on the rear, and it is almost 3 years old. Am I correct in thinking the noise indicates a fault? The battery shows 13.2v, and at the output (no load) it is 218v. I have tried charging the battery by leaving the UPS on overnight with PC turned off(I normally do anyway) but it has made no difference. Before buying a new battery I just wanted to get some opinions on this. In fact I can buy a new Dynamode for little more than the cost of a new battery, it is just that current models have those annoying IEC sockets on them instead of British 13 amp type.

Thanks in advance for any advice.

  howard64 18:06 27 May 09

sounds like a very low output voltage! mine puts out 245V on no load dropping to about 239V when the pc is first switched on and booting. Returning to almost 245V when the pc is on but idle.

  DieSse 00:10 28 May 09

Possibly you have a mains input voltage issue - did you check that too?

What kind of buzzing is it?? A proper alert signal?? Or a low level transformer mechanical buzz (if you're familiar with those)??

  Dave-dxer 08:41 29 May 09

Thanks for the response. I admit I did not check the mains input voltage. I have never known it to be unstable here in central England. For the past 24 hours I have the UPS powered up without any load, just waiting for the problem to appear. When it is next buzzing I will then test the mains input voltage together with the output voltage and report back. This could take some time, the fault being so intermittent.

When the problem occurs, at first it is often (but not always) an angry sounding low level buzzing which varies in pitch and intensity. Then it becomes a loud angry buzzing at a stable pitch. You can hear it throughout the house! I feel this is a proper alert signal although the red light on the UPS does not come on. The instructions say the buzzer indicates either a DC or AC power overload. In my situation, I don't see how this can be causing the buzzer to sound. I have measured mains input voltage at 239v-242v. I will post again when I learn anything new.

  Dave-dxer 08:44 06 Jun 09

I left the Dynamode UPS charging the battery for 3 days without problem. Output was then around 245v without any load. Connected the PC & LCD Monitor back up and all fine for 2 days. It began to buzz this morning at 1.30am! Input voltage is normal at 241v, but output (no load) was down to 220v. This suggests to me that it is the battery that is causing the problem. I plan to buy a new one. I will report back in due course!

  Dave-dxer 09:20 20 Jun 09

Just to close this thread - I installed a new battery into the UPS 9 days ago. No problem since then. My UPS has been supplying power to my PC, which is in use 24/7 since that time.

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