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Old 23rd October 2007, 02:49 PM   #1
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Default How to convert a 220v Chinese amp to 110v for US use

Greetings

I bid and won an 110volt 85watt per channel amp on a Chinese sellers list on eBay, however when they shipped it, I rec'd a 220. Multiple attempts to open discussion with the seller have failed, so it looks like returning it is out of the question.

Other than using a voltage converter, can any of you help me understand the basics of how to rewire this for 110? I am fairly savvy but not an electronics wizard.

Secondly, I wont hold you responsible if the house burns down.
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Old 23rd October 2007, 03:26 PM   #2
Svein_B is offline Svein_B  Norway
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You will most probably need to either use a step-up transformer, or replace the power transformer.

Why not open it up and post a picture of the internals.

SveinB.
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Old 23rd October 2007, 06:05 PM   #3
dre7 is offline dre7  United States
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SvienB is right. Post a pic. You might get lucky and the power transformer might have multiple taps on the primary.
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Old 23rd October 2007, 07:05 PM   #4
EC8010 is offline EC8010  United Kingdom
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Don't you use 220V for your washing machines and cookers?
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Old 23rd October 2007, 07:14 PM   #5
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Quote:
Originally posted by EC8010
Don't you use 220V for your washing machines and cookers?
Yup!

Dryer and oven outlets here are 240V

Heckuva lot better balanced for hum too than the 120V line.

Cheers!
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Old 23rd October 2007, 07:49 PM   #6
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Most power transformers I have seen fall into two categories:

1. Primaries only for ~115V

2. Primaries for ~115V (parallel) and for ~130V (series)

You hardly ever see ones where the primaries can only be wired for ~130V. That said, it is from China, so most anything is possible....

I hope you understand what parallel and series wiring means. If not then please read the SAFETY thread at the top of this forum. Your life may depend on it.
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Old 23rd October 2007, 08:04 PM   #7
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I would guess that your transformer is only capable of 220V or otherwise there would be a switch or something to accommodate either 110 or 220V. That's my guess. We'll never know until we see under the hood.

I would be careful strapping this to a 240V mains. Some things may a shortened life unless the power supply can take it. I'm sure the dryer would make a nice equipment stand though!

Hopefully the transformer is labeled so you can determine the secondary voltages. If not carefully make a reading with a multimeter. You should be able to find something to replace it from Hammond Mfg. I personally recommend something with 117V primaries.

My understanding the ideal transformers are:
EI = tube amps
toroid or R-Core = transistor amps
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Old 23rd October 2007, 08:29 PM   #8
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Quote:
Originally posted by whitelabrat
I would guess that your transformer is only capable of 220V or otherwise there would be a switch or something
Most often there is no switch. I would suspect it is possible to rewire the primaries because they have 100-110V mains in Japan... That is a market the Chinese can't afford to neglect.

It isn't that easy to replace the power transformer. You will need all the specs on the existing transformer to match up all the secondaries - heaters included.

A step-up transformer would be wiser than trying to replace the existing power transformer in my opinion.
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Old 24th October 2007, 01:52 AM   #9
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Hi

Working the other way in OZ, I ran my
Eico HF30s and Dyna Mk4s, both
110/117v primaries via well filtered
transformers 250v down to 110v and
it all worked well. The Eicos ran a bit hot
as they were designed for 60hz. Going
the other way and running 50hz designs
at 60hz will I believe be less strain.
Try and find a good isolation transformer then
add some additional filtering and you
may have a very smooth US supply 110v/60hz
or run it off the washer/dryer supply. I wish
the whole world would settle on 220v/60hz!

regards

AnthonyPT
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Old 24th October 2007, 03:16 AM   #10
wa2ise is offline wa2ise  United States
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Quote:
Originally posted by whitelabrat


I would be careful strapping this to a 240V mains. Some things may a shortened life unless the power supply can take it. I'm sure the dryer would make a nice equipment stand though!


Be careful with the dryer outlet, as those are usually fed by a 30 amp circuit breaker. If a short happens on the amp's power cord (likely just 18 guage wire) it would literally burn up. You'd need some form of fusing, on both hots, ahead of the thin wire power cord.

If you own the place, you could have a 220V 15 amp circuit installed. These are usually used for bigger window air conditioners. While you're at it, run a 3 wire (2 hots, and a neutral) plus ground line, so you can also power 120V equipment from this new circuit as well.
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