Trying to match small AC transformer - 240V primary 12.8V secondary

Hi all,

Having found an open primary in the small transformer providing standby power to a Yamaha home theatre receiver, I want to source a replacement of course.

The transformer is marked on the side:

XW608 AO TAM M 0118

and has no voltage or power specs on it. On the schematic there is a voltage shown across the secondary of 12.8V AC; the primary is 240VAC since this is an Australian unit.

The transformer is physically small (about 30x30x30 mm, or roughly an inch and a bit on each side) so I am guessing it has a rating in the milliamp range for the standby switch, IR receiver and a relay to switch on the main PSU.

Can anyone offer me guidance on sourcing a replacement? Searching for the markings via Google hasn't turned up anything useful.

Thanks for any help,

Matthew.

Reply to
Matthew Kirkcaldie
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Matthew Kirkcaldie wrote in news: snipped-for-privacy@news.sydney.pipenetworks.com:

That's strange. Transformer primaries don't open very often. I would be inclined to dig deeper to find out why there's an open circuit (internal fuse open? Bad connection? Melted wire?) and whether there is any fault downstream of the transformer (shorted component?).

Reply to
Jim Land

Don't know the reason, but I have removed it from the board and there is infinite resistance across the primary terminals and no visible damage to the transformer or the board it's on. Fuse is intact. The unit would be about 5-6 years old I reckon.

Reply to
Matthew Kirkcaldie

Any small transformer with an approximately 12V output should be fine.

Reply to
James Sweet

Small transformers are impedance protected, the windings can be damaged by power surges or an overloaded secondary. If the unit works after replacing the transformer, it was probably just a surge that popped it.

Reply to
James Sweet

Mebbe it has a faulty or tripped thermal protector ?

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Cheers .......... Rheilly P
Reply to
Rheilly Phoull

Thermal protectors are fitted to prevent overheating etc. Usaully you can by pass same, and "fix" them, but as theyre fitted for a reason( not used to our extreme heat?) they often fail. The tranny suggested is probly close enough.

Reply to
Jonno

The markings will be house numbering, either from Yamaha or their chinese part supplier. The 0118 will be a date code - week (probably) 18 of 2001, and googling that will not uncover anything helpful.

As others have said, any comparable unit with a 12v6 secondary will be fine. Any downstream elctronics which are voltage sensitive will have some supply regulation, to guard against mains input variation.

Apart from the Jaycar unit mentioned, Altronics have one which has dimensional info at

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'tis a tad weightier, implying to me that it has more iron or copper - both good things.

Even Trickie Dickie has one

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Which one is for you depends on how critical size is, and how near you are to the supplier.

Reply to
rebel

In my professional repair life, I replace trannies in hifi units all the time, that have primaries that have gone open for no apparent reason. Yes, sometimes there is a thermal fuse in the primary, and yes, sometimes it's connected across a couple of external pins so can be temporarily bridged for test purposes, but I find it rare to then come across a fault downstream, that has caused a genuine overheat that has led to the failure.

Arfa

Reply to
Arfa Daily

**Yamaha are usually pretty helpful and not stupidly priced for spare parts. Try them. The part will fit like a glove.
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Trevor Wilson
www.rageaudio.com.au
Reply to
Trevor Wilson

I've not had cause to use them for audio parts, but their computer side is one of the worst I've ever come across and put me off them as a company.

--
*Can fat people go skinny-dipping?

    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

**Your lack of local knowledge is duly noted. Matthew posts from Australia. The local Yamaha distributor provides an excellent backup for their products.
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Trevor Wilson
www.rageaudio.com.au
Reply to
Trevor Wilson

very small 50/60Hz transformers can be a right pain, as the wire gauge is so damn fine. Its extremely hard NOT to slightly damage, say, 44AWG magnet wire when winding such a transformer.

Low power transformers must have extremely high magnetising inductance AND low volume, so require silly numbers of turns of astonishingly (vanishingly more like) fine wire.

One I used in an OEM UPS' had, IIRC, 11,000 primary turns, of (again, IIRC) 44AWG. Now 41AWG is about 0.09mm outer diameter; 11k turns is thus around 70mm^2, ie 8.4 x 8.4mm, which is about the cross-sectional area ISTR for the primary winding.

And we had quite a bit of trouble with those - although they were made in Mexico, for a very low price - all of which was related to the termination.

Cheers Terry

Reply to
Terry Given

**Again: The Yamaha distributor in Australia is pretty good.
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Trevor Wilson
www.rageaudio.com.au
Reply to
Trevor Wilson

Is there just the one for all Yamaha products? In the UK I found the one which dealt with their pro audio fine but not the one for computer stuff. It was some time ago when CDW was newish and expensive. But I've got a long memory. ;-)

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*If God had wanted me to touch my toes, he would have put them on my knees

    Dave Plowman        dave@davenoise.co.uk           London SW
 Click to see the full signature
Reply to
Dave Plowman (News)

**Yep. Hi fi, computer and instruments. One big company. Japanese owned. Good service and reasonable prices.
--
Trevor Wilson
www.rageaudio.com.au
Reply to
Trevor Wilson

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