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.
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?).
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.
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.
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.
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.
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.
That tranny will work just fine. The only thing that I would say is that power transformers in domestic equipment are usually what's known as a "designated safety component". This means that they formed part of the original design approval which declared the unit physically safe - it won't set fire to your house in the event of it failing - and electrically safe - it won't make the equipment live in the event of a breakdown of the insulation on the winding wire or terminations. You can identify components which form part of a safety spec, and are thus "designated", because they have an exclamation mark inside a triangle, marked by them on the schematic.
If you do substitute a non-Yamaha transformer for the original, this would almost certainly compromise the original safety approvals for the equipment, and if there were any unforseen unfortunate consequences down the line, Yamaha would have no liability at all.
Almost certainly, replacing this tranny with a substitute, will cause no problems at all, but I think that you should be aware of exactly what you are doing for your own peace of mind. For what its worth, as a professional repairer with a legal duty of care to the public, I would never substitute a transformer that is going to run 24 hours a day, as a standby tranny is, nor would I recommend others to do so. At the very least, I would try to check, through the suppliers or even directly with the manufacturers, that any tranny you intend to use is rated for continuous operation. I would also contact a Yamaha spares agent to check the price and availability of a genuine replacement, after you have proven that all is well by checking with your substitute in place. Not trying to put you off or anything, just advice ...
Just killfile him Arfa. His signal to noise is about the highest of any newsgroup contributor so really not worth wading through for the 1% of useful stuff he posts.
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