[oneguy]

My -31 doesn’t have one either but I plan on adding one. I believe it is combat transverse-mode noise.



http://www.surplussales.com/Transformers/Pdfs/tp-91092-31_N.pdf

 

[Zenvota]

I believe it is combat transverse-mode nois

Yup, additional traverse noise attenuation, the units already do something like 60db. Im very curious about the jumpered ground and neutral though, I thought the grounded neutral secondary was an internal thing, neither of my units do this.

 

[zilch0md]

Yup, additional traverse noise attenuation, the units already do something like 60db. Im very curious about the jumpered ground and neutral though, I thought the grounded neutral secondary was an internal thing, neither of my units do this.

I'm really surprised to hear this. I thought all of the Topaz and alternate brands of these transformers were manufactured with grounded-neutral secondaries. Maybe some of them have been modified over the years by previous owners, but it's possible some were actually manufactured that way. ???

You must have already been inside and had a close look, but for anyone wanting to know, without opening the transformer, whether it has a grounded-neutral secondary or a floating-neutral secondary...

While a load is pulling current from the transformer, unplug the transformer from the mains. The load will completely de-energize the transformer.

Then, unplug the load and use a multimeter to check the continuity between ground and first the hot, then the neutral socket of the transformer's power outlet. I would expect neutral to be grounded, but if not, your transformer is well-suited to working on open-chassis equipment that has to be tested while energized - the number one reason people modify them to float the secondary.

Less known, is that a floating secondary can prevent ground loops and will also prevent backwash noise from DACs and gear equipped with switch-mode power supplies from polluting other components. Never plug more than one load into an isolation transformer with floating-neutral secondary.

 

[Zenvota]

thought all of the Topaz and alternate brands of these transformers were manufactured with grounded-neutral secondaries. Maybe some of them have been modified over the years by previous owners, but it's possible some were actually manufactured that way.

On your unit the secondary neutral is grounded at the output receptacle?

 

[zilch0md]

^ No, it's not grounded at the receptacle, but under the coils somewhere.

At the receptacle, I've proven with my multimeter that Neutral and Ground are connected.

 

[zilch0md]

 

[DaaDaa]

I just got a 1KVA 0.001pf topaz that when plugged in has a loud hum by itself. a mechanical hum that can be heard from a 10 feet away and also travels into my amp and makes my amp noisier. is this normal? do they have a hum by themselves?

 

[Zenvota]

I just got a 1KVA 0.001pf topaz that when plugged in has a loud hum by itself. a mechanical hum that can be heard from a 10 feet away and also travels into my amp and makes my amp noisier. is this normal? do they have a hum by themselves?

That sounds a bit too loud.

I have a 91092-31 that's dead silent and doesn't vibrate and a 91092-12 that has a slight hum and vibration only audible from inches away.

What is your exact model number? Some pictures could help to.

 

[DaaDaa]

it is 91001-22

 

[DaaDaa]

i just needed to know if it is normal or not. it is going back to the seller.

 

[Zenvota]

i just needed to know if it is normal or not. it is going back to the seller.

Keep this post for reference if you happen to take it to an electrician for testing.

 

[DaaDaa]

thanks man. that's great.

 

[Zenvota]

thanks man. that's great.

You're welcome, good luck. When you're doing a listening test, use something taxing and elaborate, hifi recordings with lots of room ambiance, acoustic instruments, etc. Should be an easily noticeable improvement, unless your equipment already has elaborate filtering that reduces all the common/traverse noise.

 

[oneguy]

I finally finished my 2.4 kva beast. Highlights include silver plated 10 Awg Teflon wiring, EMI/RFI resistant fuse holder and and everything needed to accept up to 20A on the primary side. She is heavy! I included the gallon jug for size reference.

 

[Zenvota]

I finally finish my 2.4 kva beast. Highlights include silver plated 10 Awg Teflon wiring, EMI/RFI resistant fuse holder and and everything needed to accept up to 20A on the primary side. She is heavy! I included the gallon jug for size reference.

Wow cool xD innie photos?