Buzzing sound from power conditioner

mwilson

Member
2021-09-13 3:44 pm
Greetings!

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!

Cheers,
Nick
 

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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.
 
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mwilson

Member
2021-09-13 3:44 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.

Cheers,
Nick
 

jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
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.
 
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jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
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.
 
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mwilson

Member
2021-09-13 3:44 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)

https://www.mouser.com/datasheet/2/378/201711289352991617-2307139.pdf

Thank you!
 

jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
FIRST the cap Mr. Wilson. This Chinese made device is able to switch 120V 20A so 2.4 kW. That relay is likely for surge protection ("slow start") at power on. It will always be powered on I think. Then it will always hum too.

An exchange will simply get another of the same quality...

Yes sir.
 
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mwilson

Member
2021-09-13 3:44 pm
An exchange will simply get another of the same quality...

One of my concerns too, hence my post here on diyaudio. I really appreciate all the help so far, and later today I'll take the unit apart, desolder and measure the capacitor, and report back. While at it I'll also swap the relay with that from the other unit, and will see if the problem goes away.
 

jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
I made a mistake by thinking it is a 12V relay but it is a 48V type. Around 20..23 mA at 48V.

Now you could try out a larger value for C2 with the same voltage rating even with crocodile clips if you can handle those safely. In parallel with the current one. If the buzzing stops it is the cap for sure.
 

jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
Now I recently acquired a NOS/NIB OEM made 100 Euro mains filter (never pay too much for a brand name) with the same relays by the same manufacturer. I just checked. Wait a minute, I take a bite of one of their spring rolls. Delicious!

Mine has even 2 of them in the 12V version and in this device they switch groups hence the mix up I made :) Your device has the relay to switch on the transformer I think. They are fed by a 12V SMPS. The relays are dead quiet.

Now check what is not according the book of OCD audiophiles....
 

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mwilson

Member
2021-09-13 3:44 pm
The capacitor is 47uF/63V. I don't have any other capacitor on hand, and just realized that I don't have desoldering wick, so I will put this off until I swing by my office later in the week and grab either a spool of that or a solder vac from the shop so I can swap the relays. I'll also check and see if we have any larger capacitors while at it. I'll report back later.

Once again, I appreciate all the help!
 
Oh, and one more thing I have had happen to me: blown or open single rectifier in the bridge. Check those too if relay supply weak.

Replacing it solved the no charging problem in an LED auto light (it comes on when mains fails, if you want it to). Made in China.
The sales guy said batteries are old, so a friend gave it to me.

I checked and found charging voltage was lower than needed.
Powered off, disconnected from mains, found and changed the stupid 4007.
He said how much...I said it was from a scrapped circuit, anyway those are 0.10 Euros per dozen or so.

He is a friend, he was happy that his light was working again. No charge...

Try and put a higher voltage rated capacitor if you can, 48 x 1.5 = 72V
80V or 100V would be safer.
 
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mwilson

Member
2021-09-13 3:44 pm
Found a 470uF 100V polarized cap. Think that will be a good replacement for the 47uF 63V that's currently there? Pinout footprint is larger, but I figured I have sufficient vertical clearance to ease into the existing holes (thinking of covering up the exposed legs with similar gauge wire jacket, like from Ethernet pairs). I'll also check the DC voltage as advised. I will be away for a few days but will report back toward the weekend.
 

jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
Missed the update, sorry. Don't replace the relay as this one has seen not much hours AND desoldering/resoldering won't make relays any better. First the cap!

A little bit surprised to see that device hast cost $4,914.95...... just when I thought my German made brand new isolation medical transformer was expensive with 75 Euro :)

Now if that thingie would be mine I think I wouldn't take a random polarized cap but I would order a known good cap like a Panasonic FC 220 µF 100V (code: EEU-FC2A221L) or the Panasonic FC 100 µF 100V (code: EEU-FC2A101L
) if that fits better physically plus 4 new diodes by a known good brand just in case if only to prevent peeling off of PCB tracks when soldering a few times.

Measuring the diodes is a must.
 
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