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Re: YAMAHA TX81Z Fried transformer.


 

Ross,
?
Usually the transformer will smell like burnt laquer if it's pooched
?from overvoltage, as sounds like the case here.
Since the power supply needs to produce +5VDC and +/- 12VDC for logic and analog rails,?you should be able to measure the output of the transformer input side and output. The input should be whatever the local line voltage is ( 120 or 240) and the output of the transformer should be 6 to 8 VAC on one tap and maybe 15 to 20 VAC on another output tap which may be center-tapped ( divided into two sections) If both are good or even close then the problem is further "downstream" , maybe bridge rectifier or regulators or look for electrolytic capacitors with swollen tops ( another sign of overvoltage) all the components, aside from the transformer are relatively cheap, if you can identify the failed ones.

Cheers,
Gregg


--- On Thu, 8/4/11, Ross Clement wrote:

From: Ross Clement
Subject: [YamahaDX] Re: YAMAHA TX81Z Fried transformer.
To: YamahaDX@...
Received: Thursday, August 4, 2011, 5:43 AM

?


--- In , "michaelcairns2011" >
> Hey, I'm new to the hardware synthesizer game and recently purchased a YAMAHA TX81Z from the us, overcome by excitement i impatiently threw on a cheap plug converter and plugged it in, at first the unit started to physically hum then within 8 seconds died.
>
> I've opened up the unit and its quite clear to me that i have fried the transformer (everything else appears fine)
>
> Would i have to contact Yamaha directly to get a new transformer ?

I'm not an electronics person, and I pass on some semi-relevant information.

It's possible that other components have gone even if they look OK. I've seen a very skilled electronics academic investigating a device which had also had some power supply related carnage. From the schematic, he was quickly able to work out what voltages should be present in which parts of the circuit, and to pipe these in directly. And in this case, the unit then fired up properly, meaning that the fault was only in the power supply. Not knowing much about electronics I found this fascinating because I presumed that replacing components would be the way to find out what works and what doesn't. He did say, before we managed to fire it up, that power supply carnage might have fried the digital electronics on the board, which would then make it a write-off.

Someone similarly skilled and equipped, even if they don't know the TX81Z, might be able to quickly work out whether it's just the transformer or not, before you try to buy a transformer which might be expensive, and may not be the only fault. In my case, it was a Roland Guitar/MIDI converter, and emailing Roland UK and asking for the schematic resulted in a PDF being sent by email the same day.

Of course, if you don't know someone who can have a poke around (safely), then it may cost more to get the unit debugged electronically. But, I pass this on in case it's a vague approximation of useful information.

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