Medical-Grade Isolation Transformer Repair

[Lazarus Short]

Back in Iowa at "Cornstock" in 2019, I was given a Medical-Grade Isolation Transformer. I got it home and ran some gear through it. It was noisy. Eventually, I suspected the SG44's, two of them, and found that they were thermistors intended to limit the initial inrush of current. They were cheap, so I ordered some from Mouser and they arrived in two days. I put two new ones in, put the case back on and made up a cord for power output. The power outs are those inverse ISE plugs, but most of my gear does not use ISE cords.

Then...I plugged a CD player into it. No noise! The shop system is already on a small Medical-Grade Isolation Transformer, so this big one (nine outlets) will go to the main system. I think I'll call Micro Center and see if there are adapters so I can adapt to ordinary two-prong plugs... Oh, I just saw that the thing retails for seven hundred bucks!

https://toroid.com/product/isobox-isb-100w-1000va/

 

[George S.]

Love to have one, but I need to run a dedicated line off the breaker first. So many things to do and so little time. That's a nice unit.

 

[mr_rye89]

I have a ONEAC 500VA isolation transformer that I used to use in my system, didn't do much for me there. It's now under my bench for working on series string radios/TVs.

 

[George S.]

What one did Joe recommend a couple years ago? I've searched for that post and can't find it.

 

[Lazarus Short]

I found adapters on ebay. Micro Center is out - no local phone number, so not willing to burn gas to drive over there. They should be here in a week.

 

[Gepetto]

What one did Joe recommend a couple years ago? I've searched for that post and can't find it.

Topaz is the isolation transformer that I use. Got it from a dentist office that was relocating.

 

[Lazarus Short]

Topaz is the isolation transformer that I use. Got it from a dentist office that was relocating.

I looked those up just now, and they seem very good for audio use.

 

[8991XJ]

I have a Tice Power Block, original audio line conditioner. Just a big transformer with a couple caps on one switched option. I like it because it will increase or decrease voltage by 10% based on switch positions. Damned heavy. The additional Titan that can be piggybacked for more is another transformer connected to the first. I don't have one of these.

I like the idea of cleaning the power coming in no matter what the argumentative naysayers believe about the last 3 feet of power delivery can't make up for the rest of the system back to the generation station.

 

[Lazarus Short]

The outlet adapters arrived today, so I installed them and hooked everything up, including of course, the Quiet-Lines unit. I can now hear notes more as separate sonic events, and micro-dynamics are improved. Low-level information is easier to hear, and I suspect the noise floor is lower. The isolation transformer doesn't get warm, and doesn't hum. It's an all-around big improvement.

 

[J!m]

I had an old one of these years ago, and the unit itself was noisy, so I didn't give it a fair shot.

But, my intention was to run one in my basement, just outside the panel (which is right below where the stereo goes), and then run up to the wall outlet to feed the stereo some clean power.

 

[Lazarus Short]

I'm learning that like every other electronic component, isolation transformers can have problems. The four-outlet one in my shop system had gotten noisy, so I pulled it out of the system. I haven't opened it up all the way yet, but it looks like there are caps inside, and I suppose they will need replacing.

 

[J!m]

Mine physically hummed; I assume it was still cleaning up the power, but I couldn't really tell, even with the (really friggin heavy) box stuffed in a closet...

 

[Lazarus Short]

My big one physically hums when it first gets juice. I leave it on 24/7. Do you still have yours?

 

[J!m]

Naaaah. A local cruise ship captain was in desperate need of an anchor, so I had to help out.

 

[Skywavebe]

Why are people using these in the first place? Usually if a transformer based device starts buzzing or humming it is due to lose lamination in the core of the build and often times silicon caulk can solve that problem or a good epoxy

 

[Gepetto]

Why are people using these in the first place? Usually if a transformer based device starts buzzing or humming it is due to lose lamination in the core of the build and often times silicon caulk can solve that problem or a good epoxy

You cannot fix magnetostriction with any amount of caulk or epoxy...

"
Magnetostriction (cf. electrostriction) is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ. The effect was first identified in 1842 by James Joule when observing a sample of iron.[1]

This effect causes energy loss due to frictional heating in susceptible ferromagnetic cores. The effect is also responsible for the low-pitched humming sound that can be heard coming from transformers, where oscillating AC currents produce a changing magnetic field.[2]

"

 

[Skywavebe]

So you are saying the product is built wrong and can not be fixed?

 

[Gepetto]

So you are saying the product is built wrong and can not be fixed?

Magnetostriction is a function of the metal physics used in the transformer core. Not built wrong, just a practical limitation you must live with.

 

[Skywavebe]

Then they should use Toroid designs all the time? In my electromagnetics course we may have covered this characteristic but the buzzing of transformers was usually due to laminations vibrating after they had come lose due to aged epoxy or whatever they used. Thus the silicon caulk was a solution in that instance and I have seen it work.

 

[Gepetto]

Then they should use Toroid designs all the time? In my electromagnetics course we may have covered this characteristic but the buzzing of transformers was usually due to laminations vibrating after they had come lose due to aged epoxy or whatever they used. Thus the silicon caulk was a solution in that instance and I have seen it work.

Toroids too Sam. Toroids are wound from the same lamination material as E-I transformers are. Yes you are correct that if you have loose laminations or loose coil on core from inadequate potting during manufacturing, you will also get noise