[GreenKeys] Powering an ASR 33 Teletype in the UK

[Rob Jarratt]

Thanks for the information. I notice that the ASR 33 is labelled 115V, but when I looked more closely at the transformer it seems to have a 110V output. I can’t find many transformers from 220V/240V down to 115V, but there are plenty around that go down to 110V, how critical is the extra 5V likely to be? If I get a new transformer, will one with 110V output do?

 

Regards

 

Rob

 

From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of gil at baudot.net
Sent: 08 December 2012 14:49
To: r.jarratt at computer.org; greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Powering an ASR 33 Teletype in the UK

 

Hi Rob:

 

Well if you used it with a transformer before, the 33 must be a model designed for 50 Hz, but at 115V.

 

All you need is a good-old iron-core isolation transformer, with a 230V strap option on one side and 115V on the other.  They often have two identical windings on one side, so you can parallel them for a 1:1 voltage ratio, or put them in series for a 2:1 step-down (or 1:2 step up) ratio.  Pay attention to the phase of those windings on the strap side.

 

If 50 Hz goes into the transformer, 50 Hz will come out the other side.  Make sure the core is rated for 50 Hz.  The most important ting is to get one that can handle the load.  Look for a volt-amp (VA) rating on the nameplate of the 33 and get a transformer that size or larger.  Undersized transformers get hot, melt, and so on.

 

gil smith
greenkeys moderator
gil at baudot.net
www.baudot.net
Vaux Electronics: 480-354-5556




-------- Original Message --------
Subject: [GreenKeys] Powering an ASR 33 Teletype in the UK
From: "Rob Jarratt" <robert.jarratt at ntlworld.com>
Date: Sat, December 08, 2012 3:06 am
To: <greenkeys at mailman.qth.net>

In the UK our power supply is 220/240V at 50Hz, and I believe the US is 110V at 60Hz. I noticed the plate on the back of the ASR 33 I have it says 115V at 50Hz, which rather puzzles me as it is a US voltage at a UK frequency.

I did get some kind of transformer that I think went with the ASR but I am not sure I want to trust it, can anyone suggest a safe way to test it? I am tempted however to buy something new for this. There are a number of voltage converters on the market which convert UK to US, but they output at 60Hz. Am I going to be able to use one of these converters for my Teletype or do I need something different?

Regards

Rob


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