[mwhitak]

Not a trivial task!
Some digital handheld meters can measure a few thousand pf, are accurate to 1%. Any better and bench models take the prize, worth more than 6 Topaz transformers. The AC current method is a better for digital hand helds, quite a few can measure down to 1uA. There's a but. The transformers under discussion here draw a lot lower current about 20pA for the 0.0005 pf models, that's 20 x 10 ^-6 uA.. I think you'd have to trust the nameplate data. Effective capacitance takes into account a calculated measurement, could be based on the current method.
Have a look here how to calculate these values.

Not a trivial task!
Some digital handheld meters can measure a few thousand pf, are accurate to 1%. Any better and bench models take the prize, worth more than 6 Topaz transformers. The AC current method is a better for digital hand helds, quite a few can measure down to 1uA. There's a but. The transformers under discussion here draw a lot lower current about 20pA for the 0.0005 pf models, that's 20 x 10 ^-6 uA.. I think you'd have to trust the nameplate data. Effective capacitance takes into account a calculated measurement, could be based on the current method.
Have a look here how to calculate these values.

Thanks One and a half ! Great stuff ! I have a Fluke 87 somewhere...but I see it's not up to the task.

 

[One and a half]

Finally receiving the 2.4kVA Topaz, here is a list of inspections and tests for 'older' transformers.

With the AC power totally unplugged from the Transformer, open both ends of the terminal boxes.
1. Look for debris, gunk dirt, especially on the terminals. A quick spray with Electra-Clean, or Iso-Propyl, with a clean rag and remove any contaminants. Don't go overboard with the spray, since the chemicals may dissolve any labels.

2. Check the connections, make sure the are tight, but not FT. The earth/ground connection is very important. This 2kVA had the shield wired to the incoming neutral which was rather odd, it should be on the earth chassis connection. Compare the voltage you are to use with the Topaz Bulletin 05160-001-TI REV A August 1984. I removed it to measure what was on it, close to 1/2 line volts on the primary.

3. Obtain an Insulation Resistance (IR) Meter. An IR meter applies a DC voltage on the transformer to measure its insualtion resistance. The voltage applied needs to be 2 x the working voltage on the transformer. For 120V systems, use 250V, for 230V systems use 500V. Since the IR meter is DC, it will not jump to the secondary from the primary or vice versa. The one I use is here. There are many others.

Connect the red lead to H1 and black lead to earth/ground.

Keep the meter in test mode on for at least 30s and observe the readings.
The minimum is 1000 M Ohm. The 2.4 kVA delivered Topaz had a reading of 2457 M Ohms - Brilliant!

Disconnect the Red lead from H1 and connect to X1, leave the black connected.

Keep the meter in test mode on for at least 30s and observe the readings. The minimum again is 1M Ohm, with the same voltages applied as before.

If all IR readings are good, then, there's good confidence to apply power, but not yet.

4. Prepare the connections to the line and the load, make sure that the connectors on plugs if you use them are all good and the connected right way round. Leave the connections off the transformer for now.
Use the IR meter to test the cable, same levels for voltages apply.

This time connect the red lead of the IR meter to the hot conductor (Black for USA/Canada, Brown for IEC) and the earth/ground cable. Ensure that any ends don't touch metals. Start the test, it should show open, or OL. If less than 1M Ohm, check the connections again. If it's an old cable, it may have to be retired as a lot of moisture contributes to a low reading.
Repeat the test for the white cable (USA/Canada, Blue for IEC), and compare with the hot.

There's then no shorts in the connecting cables, so now they can be connected to the transformer terminals.

5. With any multi meter, connect the leads to the output of the transformer to X1 and X4. I used a small Variac to gradually wind up the voltage, but this is luxury. Power on the primary of the transformer and you should see 120V or 230V depending on which config you have.

6. Leave the transformer on no load for a 'while' at least 3-6 hours, to listen for buzzes and measure the case temperature. Use your hand to gauge the temperature, the 2kVA was barely warm, and you could just hear a very faint hum with an ear about 3" from the frame.

7. If that's all good, the transformer is ready for use.


A) IR testing is at elevated voltages. Touching any terminals or probes while the IR test is on, WILL give you a very nasty bite. After the test, allow a few seconds for the voltage to discharge through the IR meter. The IR meter will let you know if any residual voltage is left.

B) 120V or 230V live testing requires the correct PPE, glasses and gloves. These voltages will and can kill. If you are not comfortable working on systems like this don't. Seek a professional out, these tests don't take long and the meters are in every electrician's kit.

 

[mwhitak]

Finally receiving the 2.4kVA Topaz, here is a list of inspections and tests for 'older' transformers.

With the AC power totally unplugged from the Transformer, open both ends of the terminal boxes.
1. Look for debris, gunk dirt, especially on the terminals. A quick spray with Electra-Clean, or Iso-Propyl, with a clean rag and remove any contaminants. Don't go overboard with the spray, since the chemicals may dissolve any labels.

2. Check the connections, make sure the are tight, but not FT. The earth/ground connection is very important. This 2kVA had the shield wired to the incoming neutral which was rather odd, it should be on the earth chassis connection. Compare the voltage you are to use with the Topaz Bulletin 05160-001-TI REV A August 1984. I removed it to measure what was on it, close to 1/2 line volts on the primary.

3. Obtain an Insulation Resistance (IR) Meter. An IR meter applies a DC voltage on the transformer to measure its insualtion resistance. The voltage applied needs to be 2 x the working voltage on the transformer. For 120V systems, use 250V, for 230V systems use 500V. Since the IR meter is DC, it will not jump to the secondary from the primary or vice versa. The one I use is here. There are many others.

Connect the red lead to H1 and black lead to earth/ground.

Keep the meter in test mode on for at least 30s and observe the readings.
The minimum is 1000 M Ohm. The 2.4 kVA delivered Topaz had a reading of 2457 M Ohms - Brilliant!

Disconnect the Red lead from H1 and connect to X1, leave the black connected.

Keep the meter in test mode on for at least 30s and observe the readings. The minimum again is 1M Ohm, with the same voltages applied as before.

If all IR readings are good, then, there's good confidence to apply power, but not yet.

4. Prepare the connections to the line and the load, make sure that the connectors on plugs if you use them are all good and the connected right way round. Leave the connections off the transformer for now.
Use the IR meter to test the cable, same levels for voltages apply.

This time connect the red lead of the IR meter to the hot conductor (Black for USA/Canada, Brown for IEC) and the earth/ground cable. Ensure that any ends don't touch metals. Start the test, it should show open, or OL. If less than 1M Ohm, check the connections again. If it's an old cable, it may have to be retired as a lot of moisture contributes to a low reading.
Repeat the test for the white cable (USA/Canada, Blue for IEC), and compare with the hot.

There's then no shorts in the connecting cables, so now they can be connected to the transformer terminals.

5. With any multi meter, connect the leads to the output of the transformer to X1 and X4. I used a small Variac to gradually wind up the voltage, but this is luxury. Power on the primary of the transformer and you should see 120V or 230V depending on which config you have.

6. Leave the transformer on no load for a 'while' at least 3-6 hours, to listen for buzzes and measure the case temperature. Use your hand to gauge the temperature, the 2kVA was barely warm, and you could just hear a very faint hum with an ear about 3" from the frame.

7. If that's all good, the transformer is ready for use.


A) IR testing is at elevated voltages. Touching any terminals or probes while the IR test is on, WILL give you a very nasty bite. After the test, allow a few seconds for the voltage to discharge through the IR meter. The IR meter will let you know if any residual voltage is left.

B) 120V or 230V live testing requires the correct PPE, glasses and gloves. These voltages will and can kill. If you are not comfortable working on systems like this don't. Seek a professional out, these tests don't take long and the meters are in every electrician's kit.

Thanks for this write up One and a Half ! Very helpful. Will you be using any overcurrent protection (such as a fuse) on the primary side (besides the breaker on the circuit that supplies power) ? I seem to recall seeing pics of topaz units with fuseholders mounted on the primary side access plate.

 

[zilch0md]

@One and a half - Thanks for those welcome instructions!

Surely that transformer didn't leave the factory with the shield grounded to the primary's neutral. Somebody must have been experimenting and decided they liked the way it sounded (or some other reason for leaving it that way.)

Higher up in this thread, somewhere, you can see a PDF where multiple shields are used. That's the only case where I've seen somebody connect a shield (the one closest to the mains) connected to the primary's neutral, while another is connected to the earth ground and perhaps a third shield to the secondary's neutral.

 

[One and a half]

@One and a half - Thanks for those welcome instructions!

Surely that transformer didn't leave the factory with the shield grounded to the primary's neutral. Somebody must have been experimenting and decided they liked the way it sounded (or some other reason for leaving it that way.)

Higher up in this thread, somewhere, you can see a PDF where multiple shields are used. That's the only case where I've seen somebody connect a shield (the one closest to the mains) connected to the primary's neutral, while another is connected to the earth ground and perhaps a third shield to the secondary's neutral.

Yup, can swear on two stacks of bibles, the primary shield was connected to the 120V neutral. Very weird!

 

[One and a half]

Thanks for this write up One and a Half ! Very helpful. Will you be using any overcurrent protection (such as a fuse) on the primary side (besides the breaker on the circuit that supplies power) ? I seem to recall seeing pics of topaz units with fuseholders mounted on the primary side access plate.

Right, fuses I don't like. For the primary, a D curve circuit breaker will take care of the inrush and quick protection.
I need to measure the inrush current and select a breaker to suit.
To protect the secondary, a little different approach.

For short circuit a combo GFCI / RCD will work, for long term thermal protection, a thermal overload, which adjustable setting can accurately sense an overload.
To cut the power off, the primary needs to be switched off.
This can be a relay on the primary after the D curve breaker. So if the thermal overload trips, it cuts of the primary power.

Will show how this works on a drawing.

 

[mourip]

Not sure how I missed this thread. I found out about the Topaz IT over on The Computer Audiophile and have used one for a while but this thread gets the highest marks for clarity and a collaborative spirit.

Thanks!

 

[shyamwanne]

I have both a MGE and Topaz unit that are in very good condition. The improvement to the sound of my system was immense, however, I now have developed tinnitus and my ears hurt when I have either of the transformers in my audio chain. Is it possible they are producing a very high frequency or something that could hurt my ears? Would any kind of filter be appropriate to use with one of them?

 

[mourip]

Have you tried removing them from your system to rule out that something else is the culprit?

 

[shyamwanne]

Hi, yes. When I remove them from the system my ears do not hurt. As soon as I put them in, my ears hurt. That is why I am asking in this thread. My ears are sensitive to very high frequencies, so I was wondering if Isolation Transformers like these could be producing ultra high frequencies, or something of that nature, that could be filtered, so I could continue using them.

 

[zilch0md]

I can't imagine how that's happening, but another possibility is that, rather than generating high frequencies that are hurting your ears, perhaps they are just passing high frequencies that you cannot hear in their absence - high frequencies from the source signal, itself. What are you actually hearing in the treble region that causes pain? Is it more like noise than music?

 

[knowhatimean]

I could be mistaken,but, I don't believe that an Isolation Transformer would be passing along ultra high frequencies as the signal still has to pass through output transformers of whatever devices are connected to the Isolation Transformer.

In other words the IT is only affecting the input Power Supply of whatever it is sitting in front of. I highly doubt that it is an IT that is producing ultra high frequencies that your ears are sensitive to, if anything the IT only a filter, unless your ears are sensitive to existing high frequencies in the music you weren't able to hear, beforehand..

Disclaimer ; I'm not an EE.

 

[shyamwanne]

It is indeed possible the Topaz is passing high frequencies that I would not hear without it. The music is that much clearer. This would again make me wonder if there is some sort of filter I could use to filter out very high frequencies.

I had on an ultrasonic vaporizer constantly going in the house. I noticed that also hurt my ears, as when disconnected, I felt relief as well. That is what gave me the idea that perhaps the Topaz was generating (or passing through) ultrasonic frequencies.

In the music itself, I audibly hear nothing. However, just turning on the transformer I can 'feel' it even from a distance. And with the headphones on, it hurts my ears. Perhaps I am sensitive to some form of EMI?

I've ordered some EMI/RF blocking cloth to wrap the transformer in, to test this. Though that would not help anything being passed through the headphone itself. Could EMI be passed through headphone drivers?

 

[alpovs]

That is what gave me the idea that perhaps the Topaz was generating (or passing through) ultrasonic frequencies.

It is unlikely that your headphones would emit those ultrasonic frequencies. What headphones do you have?

Transformers do vibrate, especially those with a number of metal plates. But they vibrate at the frequency that goes through them which would be 60 Hz. If you ever walk in a residential area and pass by a transformer (in my area a large green box) you can hear a hum.

 

[shyamwanne]

My headphones are Audio Technica ADX5000, which are fantastic by the way

The 60hz hum from the Topaz doesn't bother me. It's the electromagnetic field. For example, I get a headache if around those large transformers or large power lines on the street for very long too. Small ones don't seem to bother me though.