Running 100V gear on 120V outlet

[cjacek]

Not sure where to post this so I default to my place here.. hope you don't mind and can shed some light on this for me...

Is it expected for a piece of gear, which is set to 100V 50/60Hz, to generate low frequency hum when run on 120V outlet? Would that 20V extra be enough to start causing problems?

 

[technoplayer]

Must be a domestic Japanese unit. They are the only ones using 100V.

Typically, theses electronics are rated for 100-120V. Running on the hi side should not cause it to generate any odd hum. Is it like a 60 hz power line hum?

 

[cjacek]

Must be a domestic Japanese unit. They are the only ones using 100V.

Typically, theses electronics are rated for 100-120V. Running on the hi side should not cause it to generate any odd hum. Is it like a 60 hz power line hum?

Yes, it was made for the Japanese market. On the back it says 100V 50/60Hz. I know I probably shouldn't be running it on 120V, even tho that could probably be higher, with all the mains fluctuations etc.. So potentially I could be getting at least 20 higher than what the unit is set to. To answer your question, yes, it's like a low level 60Hz power line hum. Not very audible, especially with music material but it's there. Can running on the different Voltage cause that type of hum? BTW, the unit in question only uses 5 watts. Thanks for replying.

 

[technoplayer]

I deal with a lot of ultra precision semiconductor mfg and test equipment.
The Japanese equipment is designed for 100V or 200V. We have no issues running them on 110/120 and 208 respectively. Again, I do not see the voltage being the issue. We DO use line power conditioners on the sensitive test gear however, but this is there to cut line noise being generated by other equipment.

>>>Try repositioning the unit away from other equipment, and make sure that it is not on the same circuit as a fridge or anything else with an electric motor.

 

[TimOBrien]

US/Canada power varies from 95-125volts.

Dont worry about it, it wont hurt it.

 

[GCalo]

You may have bad electrolytic caps in the power supply.

What is the piece of gear?

That might shed some light (not that the equipment produces light of course).

 

[cjacek]

>>>Try repositioning the unit away from other equipment, and make sure that it is not on the same circuit as a fridge or anything else with an electric motor.

I took your advice and repositioned - it did help! I had a compressor sitting on top of it which was creating extra noise. It's a lot better now.

US/Canada power varies from 95-125volts.

Dont worry about it, it wont hurt it.

You may have bad electrolytic caps in the power supply.

What is the piece of gear?

That might shed some light (not that the equipment produces light of course).

It's basically a spring reverb. I hope it's not the caps. Sounds wonderful really but still has that annoying noise. I'll try to live with it, at least for now.

THANKS AGAIN GUYS!

 

[Blue Jinn]

I have a spring reverb (PAIA kit) that also has an issue with hum. I'm in the process of reworking my "studio" space, so everything is disconnected. I did notice that the ground wire coming off my psu was disattached (it is +/- 15v) I don't know when that occured, and it uses 7815/7915 regulators, which I've read can add a lot of noise.

Is the reverb powered by a "wall wart" or is the psu internal?

We may be having the same type of problem. I am planning on changing to a LM317/337 based psu which is supposed to have lower noise, and see if that helps.

I think also (and others can correct me on this) that the "reverb tanks" themselves may be more susceptible to RFI.

Note that in my case I am pretty sure it wastn' a ground loop as I used an Ebtech hum eliminator on the gozinta and gozouta and still had hum. Do you have one of those you can use? AFAIK they are basically a 1:1 transformer, so you could save yourself about $40 and get some Edcor transformers to fashion your own.

 

[cyrano]

With spring reverbs, vibrations can also be an issue. Sometimes, the magnetic field from big power transformers will cause the metal case to vibrate a little. And that sounds an awful lot like hum.

 

[Blue Jinn]

One thing that was recommended to me, and I just haven't had a chance to try was to run the thing on batteries, it would probably work OK with two 9v (+/- 9v) to see if the hum goes away, or maybe four, as I'm pretty sure the opamps could handle +/- 18v.

 

[Beck]

Sounds like ground loop or shorted cap. The difference in volts won't cause hum by itself.

This link is helpful for the ground related issues.

http://www.tweakheadz.com/war_on_hum.htm

 

[GCalo]

For once a link that is not ho hum!!!

 

[cjacek]

Is the reverb powered by a "wall wart" or is the psu internal?

The PSU is internal. No wall wart.

Thanks. I'm gonna take much of what you said under advisement tho, truth be told, lots is just too much tech for me.

With spring reverbs, vibrations can also be an issue. Sometimes, the magnetic field from big power transformers will cause the metal case to vibrate a little. And that sounds an awful lot like hum.

Note taken. Thanks. Tho I will say that putting my ear to the reverb case, I can hear this hum / low buzz. Maybe it's picking it up mechanically through the springs.

Sounds like ground loop or shorted cap. The difference in volts won't cause hum by itself.

This link is helpful for the ground related issues.

http://www.tweakheadz.com/war_on_hum.htm

Very helpful link, Tim. Thanks a bunch.

For once a link that is not ho hum!!!

Lets stay on track (inside joke ).

 

[cjacek]

BTW, here's a photo (for those who like this sorta thing ). This was before I cleaned it up a bit. If you want more let me know and I'll post 'em.

 

[GCalo]

Yes I like that photo kind of thing!!!

 

[Blue Jinn]

Hey,

That looks pretty cool. It may be a ground loop, Does the power cord have two or three prongs. You could get a "hum eliminator" from Ebtech, to try out, that transformer isolates the input/output. Those are around $50-70 give or take, but it's worth having when you can't solve a problem otherwise. (I just followed Beck's link though and looks like the Behringer is about $40 or so)

It looks older, so caps ont eh PSU might be an issue too. I think we've all ruled out the minor voltage difference.

 

[cjacek]

Yes I like that photo kind of thing!!!

Well, then I'm including a few more just for you. ........

Hey,

That looks pretty cool. It may be a ground loop, Does the power cord have two or three prongs. You could get a "hum eliminator" from Ebtech, to try out, that transformer isolates the input/output. Those are around $50-70 give or take, but it's worth having when you can't solve a problem otherwise. (I just followed Beck's link though and looks like the Behringer is about $40 or so)

It looks older, so caps ont eh PSU might be an issue too. I think we've all ruled out the minor voltage difference.

Thanks! It's a two prong cord. Yup, will def consider the hum eliminator but also take into consideration the PSU caps tho...... See that large capacitor on the right? The original owner said his tech added it to reduce hum, as he said the stock power supply was "under powered". Not sure what he meant or did but that's what he said.

Yup, not worried about the voltage issue anymore.

The unit itself is as common as winter in July. Hardly any info on it. It's built real well tho. All metal, even the knobs. Real VU meters. Lots of features, even a mic preamp. Never seen a spring verb like this. Hard to date it but looks late 70's to early 80's.

 

[GCalo]

Very nice for a guy from Massachusetts.

Haverhill? I had a professor from Haverhill.

I have not been there in 40 years!

 

[Blue Jinn]

Interesting about that psu mod. The trafo looks decent enough, not sure what he meant by "underpowered."

Looks like the circuit board on the right is a pretty conventional power supply, you might see what it is putting out (maybe +/1 12 v ??) and consider replacing the psu, plenty of room in that box, or at least swapping it out and see if it makes a difference.

Otherwise, way cool way way cool.

 

[cjacek]

Very nice for a guy from Massachusetts.

Haverhill? I had a professor from Haverhill.

I have not been there in 40 years!

Forgive me but I don't follow... Are we on the same topic? ...........................