I acquired a Yamaha yg15 amp. The power transformer is toast. I'm looking for a schematic for it. I've been all over the internet without any luck. What I'm mainly looking for is the output  voltage on the rectifier circuit. Thinking about battery operated.

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Have you tried Yamaha website?

If the power transformer is bad, it will cost more to fix it than to buy another.

I had a Behringer 10watt guitar amp that did the same thing. I removed all the old electronics(leaving the speaker and metal chassis) and made a 1watt 9volt Ruby amp and installed it. Works great and is the perfect little practice amp. It actually sounds better than the amp I replaced.

You could buy one of those 2.5watt amps and a Psycho Kob from Gitty and wire them up using that cabinet and speaker. I use a walwart instead of battery.

You may also find a similar small amp at a local pawn shop for little money.

I'm mainly looking for the rectified voltage. Yamaha can't or won't help. I have a couple salvaged transformers that possibly could work. Not a big deal!

photo of the dead transformer? are there any markings on it? are you sure it is the transformer and not the diode bridge in the rectifier?

No photos or markings(first thing I looked for, only qc sticker). I gutted the transformer to make a pick up. The transformer's primary side was fried. The rectifier bridge is fine(tested with ohm meter). In hindsight I'm thinking I should have rewound the transformer pita but doable. I may hook a 9v a.c. wall adapter up and see what happens, at this point nothing to loose. Really would like to use a 12 v gel battery for portability.

Get the model number off the main chip and google it for specs. That way you find out the operating voltage, it could be 9volts, 12volts or 18volts DC.

Its a tda2030a, from what I've read 6- 36 volts. So I think I'll split the difference and go with 12 volts and keep it on the safe side. What's your thoughts?

TDA2030A  data sheet here https://www.st.com/resource/en/datasheet/cd00000129.pdf

says 18W output into 4 ohm load with +- 16V  . were there 2 windings on the secondary?  it looks like it can be hooked up to a single supply but the chart of output power to supply voltage suggests yoy will need around 30V DC to get 15W into a 4 ohm load. or around 36 V if it is an 8 ohm load.. chart starts at 24V with 10W into a 4 ohm load. so you could series 2 gel cells for 24 volt it would work but not push the amp

I could do 3 gel cells for 36 v, I don't plan on cranking up the amp and grinding away!

good ideas

When my amp went out, it also fried some output caps along with the overheated chip. So have a good look at all the components and check them with a voltmeter if you have one.

Damn good idea about the specs for the chip, didn't even think about that. Thanks all other components check out. If it had been the secondary side I would probably scraped the unit.

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