pioneer a 777

The 230/240v unit has pairs of fuses (2A) for each primary and they go into the matching 230 or 240 volt fuse clips. Check they are intact and installed correctly.

The multivoltage units can have problems with the rotary voltage switch on the back, but it's not wired in such a way that would allow two different primary voltages to be applied. That said, rotate it carefully and check it anyway.

I'd be checking the primary applied voltages to each transformer, the bridge rectifier etc.

I'd also be putting a DBT in line.
Of course, a dim bulb tester. :) Anyone poking around inside an amplifier testing secondary voltages should know what one is.

If one were to type "DBT Diyaudio" into Google, one would find this quite informative thread:

Here's one I made up the other day for a friend who buys old gear and just plugs it in!

He got a stern talking to and he is now running a DBT (Dim Bulb Tester) and an RCD/ELCB (Residual Current Device/Earth Leakage Circuit Breaker) in line when powering up vintage 'finds'. :)


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I've been advocating for dim bulb testers for about 30yrs now and have discussed it widely here and elsewhere. I refer to it as a ballast lamp. (Well that is the function it performs and I am an EE lol) My comment was about the use of the acronym DBT which to most audio folk (16yrs in the industry before I bailed) has the specific meaning: "Double Blind Testing" and there are at least 30 other common usages for the acronym. I try to avoid undefined acronyms particularly around non native English speakers, that's really all I was trying to say.

I am not sure your good message about the lamp was received in any case judging from the question just asked.

RCD/ELCB in the U.S. and Canada are called GFCI or GFI for ground fault (circuit) interruptor.


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u take out a two transformers frome amplifier.and one give on secondary 42 volts ac.another give 32volts ac.i put on 220 volts.
did one trafo its wrong???

If the transformers are supposed to be identical it could indicate that the load on the two transformers is vastly different (higher current on the lower reading transformer) that there is a partial short in one of the windings (if that is the case it will get hot very quickly and should result in a blown fuse) or the voltage selector or some aspect of primary wiring is messed up. It should be fairly obvious.
Just picked one of these up today with the voltage selector damaged. The trnasformers have two, centre tapped windings. One side is 110V and the other is 10V. With a pair of transformers and the voltage selector, they are wired and combined in a number of ways to "absorb the input voltage. For example, for 240V they are all wired together and the voltage selector jumpers the two transformers together. so, 110 + 10 + 100 +10 = 240.

Hope the helps.