Using stepdown transformers without blowing things up


Old 12-28-11, 03:10 AM
Thread Starter
Join Date: Dec 2011
Location: New Zealand
Posts: 3
Using stepdown transformers without blowing things up

Recently I moved back to NZ where we use 240V AC and went about setting up my recording equipment from Japan which uses 100V. I have run some of the equipment here before without trouble. However, this time I managed to destroy two power converters and one powerbar (powerstrip).

Here's my step by step account, with photos.

The only thing I can find that may relate to my problem is this article, but I can't find anything else that substantiates the claims made here.
Never Use a Surge Protector with a Step-Down Transformer

Basically, my questions are ...
- What did I do wrong and what should I do to avoid doing it again?
- Is it possible to use any of my power bars at all?
- Is it worth purchasing another stepdown transformer or is it safe to run everything off my 1000W transformer?

I have developed a slight fear of electricity and would rather not destroy any of my more valuable equipment.

Here are some of the equipment ratings. Except the amplifier, most are relatively low.

This is what was plugged in when it blew.
Converter > powerbar > Mixer (100-240V/33W), SCSI drive (100V/10W), SCSI drive (100V/9.5W Max 29.5W)

Other equipment I need to be able to plug in are ..

- Amplifier 100V/100W
This in turn has the following plugged into it.
MD Player 9W, DVD 10W, Tape 25W

- 3 Synthesizers, all 100V and rated at 8W, 17W and 26W.

Other disk drives and CD players rated between 10-15W
Sponsored Links
Old 12-29-11, 04:57 AM
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Welcome to the forums. The article makes a good argument for not using surge protectors. However, what's to stop you from using a surge protector before the step-down -- one that is designed for 220v?

Add up the wattage from all of the devices and it totals much less than the 1,000 watts available from the transformer. Less than 300 watts, in fact. I wouldn't load the transformer to more than 80% (800 watts) to maintain a bit of headroom.
Old 12-29-11, 02:26 PM
Thread Starter
Join Date: Dec 2011
Location: New Zealand
Posts: 3
Thanks Rick,

Yes, the total Wattage isn't so high, so the transformer I have should be sufficient.

My main issue is having enough sockets to plug everything into. In total I need about 13, and there are only two on the transformer.

If possible, I would like to use the powerstrips I have, but before I try, I would like to know if there is any way to make absolutely sure they are plugged in with the correct orientation. Only one has prongs of different lengths on the plug.
Old 12-30-11, 03:50 PM
Join Date: Mar 2007
Location: Norway
Posts: 254
A lot of things to consider here.
Because of the risk with autotransformers this are not OK in Norway. The risk is reduced some in NZ with polarized outlets.
(some other countries use same plug but has switched neutral and live wires, so you have to test if its right.) You will at least need a real transformer, some traveling adapters works well for hair dryers, but not for electronics.
When you switch on/off the transformer you may get strange peak voltages so you should make a routine powering the transformer, and then plug in/turn on one by one load.
The transformer should be oversized by e.g. 20%
If the transformer is protected with fuse or circuit breaker, it should be on live side only, or a dual pole breaking both wires simultanously.

Remember the NZ 240 voltage is adjusted to 230 on the paper, but may vary, this will cause an unsecure voltage on the secondary side, it should be measured both with no lad, and full load to check if it is within the limits you decide as OK.
(e.g. 100V +/7 Volts)

Old 01-13-12, 12:01 AM
Thread Starter
Join Date: Dec 2011
Location: New Zealand
Posts: 3
Thanks for the responses. I took a risk and used the power bar that I had used before, the one with one prong slightly longer.

I have everything up and running. The power bar allowed me to plug in everything I needed to, with a couple of other double plugs and so on.

I daren't use the other power bars as there is no way of telling which orientation is correct.

Old 01-13-12, 03:48 AM
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Got a meter? Set it to ohms and see which prong on the other power bar goes to which slot. Label or mark it so it corresponds to the orientation of the working one. (Do this while it's unplugged ...)

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes