greetings to you guys, happy new year and merry Christmas. need help on thisYamaha p4500 burned toroidal, can't find proper replacement part, it has 3 primary leads 2 brown one black , two secondary outputs first ( 2 orange wires , one violet ) second ( 2 red wires one black ) have the schematic only but don't have the voltage output values AC, any kind of help will be highly appreciated, thanks in advance.
Post the schematic and we car reasonably guess AC voltages.
We can also do without, but in that case it's a wild guess 😉
We can also do without, but in that case it's a wild guess 😉
If the transformer is burned up, I won't even dare thinking about what the power amp section might look like...
Anyway, it looks like there is an aux supply of +/- 27 Vdc, so going by Rod Elliott we may be looking at 2x 21 Vac or so for that?
As for power amp supplies, those would have to be high enough to support 460 W into 8 ohms. That's almost +/- 90 V, loaded, and probably closer to 100-110 unloaded. AC should be somewhere in the 2x 65-70 V vicinity then.
In terms of transformer sizing, the size of the original should be a good indication if you don't have it rewound in the first place.
Anyway, it looks like there is an aux supply of +/- 27 Vdc, so going by Rod Elliott we may be looking at 2x 21 Vac or so for that?
As for power amp supplies, those would have to be high enough to support 460 W into 8 ohms. That's almost +/- 90 V, loaded, and probably closer to 100-110 unloaded. AC should be somewhere in the 2x 65-70 V vicinity then.
In terms of transformer sizing, the size of the original should be a good indication if you don't have it rewound in the first place.
amplifier section is ok al ready check each one power transistors and drivers, the toroid blown because an electrical failure, the main ground collapses on circuit breaker house, the fuse didn't blew (don't know why) main rectifier diode shorts, now both primary wires are open.
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Pretty close. You may have to put some dissipation resistors in series with the 25-0-25 though, in order to get back down to +/-27 V. I'm not at all sure what sort of current is being drawn there, so I'd just start at like 47 ohms 3..5 W and see what the voltages are like.
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