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mwilson 13th September 2021 04:06 PM

Buzzing sound from power conditioner
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This is my first post on diyaudio, so first please pardon if I've made it in the wrong category. Second, while I know a little about electronics, I'm unfortunately far from the target audience of this site—however, I'm hopeful that I could be pointed in the right direction.

I recently acquired a Furman IT Reference 20i power conditioner and noticed a buzzing sound coming from within. Though it's also an isolation transformer, there's no hum, and I've traced the source of the buzzing sound to a small PCB that appears to be a voltage regulator. I've reached out to Furman but their approach is to just return the unit to the shop and get a new one... which seems overkill and unnecessarily expensive (unit weighs in at about 90 lbs).

Any suggestions on what might cause the buzzing and how to address? I'd think it's from that black box at the top of the diodes. I'm comfortable with a multimeter and soldering iron, but not with actual circuit design and troubleshooting.

Unit works perfectly fine otherwise.

Many thanks in advance!


NareshBrd 13th September 2021 05:07 PM

It is a relay, maybe with thermal overload built in.
Common in refrigeration equipment.
See the manufacturer's catalog.
Buzzing relay is also called chatter, due to bad coil supply, or worn contacts, worn armature. Not expected on a new unit.

Unless you are experienced, do not attempt repairs on equipment on mains power.
If you get an exchange, do it, you will be out maybe shipping.
Maybe they have a known issue with this batch.

But check up first what is happening, unless it is under warranty.
You might void the warranty if you attempt repairs.

mwilson 13th September 2021 05:31 PM

Thanks for the quick reply. Yes, it's a relay.

It's not a matter of shipping cost, in fact shipping would be free to me, but rather that given the heft of the unit I'd expose it to potential physical damage.

If it turns out it's the relay, I'd be perfectly comfortable removing the PCB and replacing it. I've located it on mouser.


NareshBrd 13th September 2021 06:44 PM

A new relay should not chatter.
Seems to be made by a Japanese company. Good quality is expected.

Check the relay coil supply.

mwilson 13th September 2021 06:57 PM

I'll check the coil supply voltage. I have a known good relay (same component actually) on a now-decommissioned Furman so should be easy to test whether this is the culprit by swapping them.

jean-paul 13th September 2021 07:21 PM

The relay is by the famous manufacturer Song-Chuan that also produces spring rolls and sriracha sauce.

Replace the relay for a know good A brand one with exact the same pinout, same ratings and preferably less coil power.

Wait a minute.....

I see 4 rectifier diodes and a small cap C2. Now IF that cap is the filter cap and we assume that cap is chosen in a too small value (cheaper to maximize profit) then the relay may get pulsing DC and it therefor chatters. So please tell the brand (surely cheap quality) and the value in µF. Like Capxon 220 µF/16V. If you have a capacitance meter that would be splendid. The 832A relays consume about 1W at 12V so 85 mA. It should be minimum 470 µF in a good design.

NareshBrd 13th September 2021 07:31 PM

Also, see if the cap is a good quality one or not.
Another reason for relay chatter is overload on the relay.
Is it that the load on the unit is close to the relay's trip level current?
But if it is from a sauce maker, then the whole unit becomes suspect, who knows what else has been compromised?

jean-paul 13th September 2021 07:38 PM

NareshBrd, I don't like your suggestions at all. Their spring rolls are delicious with the sriracha sauce :)

Ahem I was not serious but I have seen some exquisite relays of "throw away quality". Therefor it is the first suspect in OEM made stuff but then I thought of the cap.

mwilson 13th September 2021 07:39 PM

The buzzing sound is same whether there is load on the unit or nothing even plugged in.

I'll check the capacitance and will report back.

Is there a specific better-quality relay that you can think of, Jean-Paul?

This is the datasheet for the relay series, my specific product is 832A-1A-F-S 48VDC (250V 30A switching, 48VDC coil voltage)

Thank you!

NareshBrd 13th September 2021 07:48 PM

No offense taken...
My point was that if cheap and dubious parts have been used, the overall quality of the unit in material and service is less than what was expected when purchasing the item.
So it will require a full inspection of the entire unit.
An exchange will simply get another of the same quality...

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