500C power on "noise", this happens once every 20 times (or so).

the_nines · Mar 17, 2012

I have my 500C plugged into a power strip.

I use the on/off switch on the power strip to power-up (and shut off) the unit only to save on the wear-and-tear of the unit's on/off switch (the volume control).

Once in a blue moon when turning the unit on (via the power strip) I hear a very brief (less than one second) vibrating sound.

What is this sound/vibration?

The unit plays fine.

buglegirl · Mar 17, 2012

Hello,

Vibrating like buzzing or Vibrating like a outboard motorboat ???

Frannie

byoungman1 · Mar 17, 2012

Sounds to me (not that I've heard it

) like the power supply caps charging up...no big deal (if that's what it is).

the_nines · Mar 17, 2012

byoungman1 said:
Sounds to me (not that I've heard it ) like the power supply caps charging up...no big deal (if that's what it is).

That's what I would tend to think.

Like I said, the unit sounds fabulous.

Thanks.

gadget73 · Mar 17, 2012

Some of my tube gear makes a buzz for a brief moment when first powered up too. I've always assumed it to just be the inrush surge on the transformer and have never paid it any mind.

Fisherdude · Mar 17, 2012

buglegirl said:
Hello,

Vibrating like buzzing or Vibrating like a outboard motorboat ???

Frannie

You need to help us out by answering Frannie's question.

Power supply filter capacitors do not make sounds. Unless something is very wrong. Power transformers do occasionally make a buzzing sound, but it usually is not of short duration. It can be loose laminations, or minor vibrations that make sound simply because the transformer itself is not tightly bolted to the chassis.

You might try tightening up the bolts that go through the end bells of the power transformer and output transformers, and then make sure the bolts holding the transformers to the chassis are tight. This is the troubleshooting equivalent of "is it plugged in?", but we need to start with the simple things first.

GYMusic · Mar 17, 2012

Like "gadget73" said, it's most likely the transformer core inrush surge - laminations vibrating in time with the magnetic field (at 60Hz).

analog · Mar 17, 2012

As has been said it is probably the inrush as the tube filaments are cold and the caps are charging. The transformer in my Anthem integrated makes a thump for lack of a better description when I hit the power button. Its done that for years.

derekva · Mar 18, 2012

But it might be good to answer Frannie's question as to what the noise sounds like...

-D

the_nines · Mar 18, 2012

buglegirl said:
Hello,

Vibrating like buzzing or Vibrating like a outboard motorboat ???

Frannie

Really don't know how to answer this.

Let's just say it sounds like a "hair clipper" the instant the barber turns it on and lasts for a second.

How's that?

larryderouin · Mar 18, 2012

Sounds like loose laminations in the Main Transformer. Tighten up all the attachment bolts and the lamination bolts. Also ensure the bolts on the OPT's are tight. You can lessen this symptom by installing current limiting varistors (soft start) at the power cord connections. Instead of a sudden jolt of current and voltage, the varistors will ramp up the current and voltage over from a few up to 10 seconds depending on the load capacity and size of the varistors. CL80's are the most popular in the 500C/800C.

Larry

the_nines · Mar 18, 2012

Thanks. I'll check it out.

the_nines · Mar 18, 2012

All bolts check out OK.

I'll leave things be.

Thanks.

dsndblm · Mar 18, 2012

Installing a current inrush limiter would most likely solve the problem. My 500C, 400 and home built SE 45 amp all made the same sound as you described before installing the CL-80 inrush limiter.

buglegirl · Mar 18, 2012

Hiya,

I use the on/off switch on the power strip to power-up (and shut off) the unit only to save on the wear-and-tear of the unit's on/off switch (the volume control).

Installing a current inrush limiter would most likely solve the problem. My 500C, 400 and home built SE 45 amp all made the same sound as you described before installing the CL-80 inrush limiter.

Also mitigates power switch burn out.

Frannie

the_nines · Mar 18, 2012

buglegirl said:
Hiya,

Also mitigates power switch burn out.

Frannie

Yup ..... sure does.

Thanks a bunch.

the_nines · Mar 19, 2012

larryderouin said:
Sounds like loose laminations in the Main Transformer. Tighten up all the attachment bolts and the lamination bolts. Also ensure the bolts on the OPT's are tight. You can lessen this symptom by installing current limiting varistors (soft start) at the power cord connections. Instead of a sudden jolt of current and voltage, the varistors will ramp up the current and voltage over from a few up to 10 seconds depending on the load capacity and size of the varistors. CL80's are the most popular in the 500C/800C.

Larry

Not to beat the same drum, but if the above was true wouldn't this "noise/vibration" be present every time I turned power on? Why does it do it every 20th time (or so)?

:scratch2:

Like I previously mentioned, the unit sounds just fabulous.

Patrice B · Mar 19, 2012

I have a Knight and an Eico doing a thump once in while when powered...

derekva · Mar 19, 2012

the_nines said:
Not to beat the same drum, but if the above was true wouldn't this "noise/vibration" be present every time I turned power on? Why does it do it every 20th time (or so)?

:scratch2:

Like I previously mentioned, the unit sounds just fabulous.

Maybe you roll a fumble on your 1d20 that often?

-D

nbndtrain · Mar 20, 2012

Sounds like it's the power transformer. Try flipping the plug.

500C power on "noise", this happens once every 20 times (or so).

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