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It is currently 16 Dec 2018, 13:53

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PostPosted: 09 Nov 2018, 09:21 
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Joined: 09 Nov 2018, 09:09
Posts: 1
Hi,

This is my first post here. I am trying to repair a Yamaha RX-V2400 receiver and brush up on my electronics skills. First of all, please let me know if this fits in this forum.

Here is what is happening:
- the receiver blew the main fuse. (blows right away with new fuse)
- did a lot of general troubleshooting
- ended up disconnecting all secondary on the transformer, still fuse blows.
- the only way not to blow a fuse is by also disconnecting the primary.

I measured the resistance on the primary: 0.8 Ohm. It seemed low given the type of transformer. But I am looking for some general guidance.


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PostPosted: 13 Dec 2018, 17:00 
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Joined: 23 Feb 2017, 02:02
Posts: 243
Your best off to just abandon the amp and try easier projects to brush up your skills.

Fixing a amp is harder than building one from scratch.

Brushing up skills goes from easy and builds up slowly step by step. Try skipping steps to a higher then not only you don't learn things and fail but you also waste your time.

Even professional dudes reparing sometimes can take months or never able to fix amps not easy job.


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PostPosted: 13 Dec 2018, 23:07 
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Joined: 26 Dec 2016, 03:46
Posts: 180
Location: Bayarea
OK, first all, you can do a "dead bulb" test.

Do you know electricity well enough. This can be dangerous. Do not proceed if you are not.

You make a box, put a light bulb socket in SERIES with the H wire ( in US, it's usually black color). This is to put a light bulb in series with your amp. Use a 100W light bulb.

Now if you turn it on, even if the primary side is shorted, the current is limited by the light bulb to about 1A. The light will light up bright. For normal amp, it's not a short, the bulb will just light up dim.

With the bulb, you can measure the voltage drop across the primary of the transformer and see is it really shorted. This dead bulb at least give you a chance to look at the voltage drop in the fault condition instead of blowing the fuse right away.

Now be careful, don't blame us if you hurt yourself as this is live wire.


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PostPosted: 13 Dec 2018, 23:10 
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Joined: 26 Dec 2016, 03:46
Posts: 180
Location: Bayarea
If you really see a short across the power transformer, AND if you are sure the secondary is open, that's not good news. Are you sure there's nothing that short out the primary. But you did say if you disconnect the primary, it won't blow the fuse. That's not good news if what you described is accurate.

But it's hard to believe the power transformer just shorted. You sure you disconnect ALL the secondaries? there might be multiple secondaries, all it takes is one of them being shorted, you can blow the fuse.

BTW, you cannot measure the resistance across the primary to determine whether it's shorted, they always read low. I am not surprised it's 0.8ohm DC.


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PostPosted: 14 Dec 2018, 02:08 
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Joined: 23 Feb 2017, 02:02
Posts: 243
I imagine probally something on secondary shorted eletronics maybe power transitors blew or its been overbiased to a short.


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PostPosted: 14 Dec 2018, 04:11 
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Joined: 26 Dec 2016, 03:46
Posts: 180
Location: Bayarea
BTW, in case you don't have the schematic. This is the service manual from Hifi Engine. Just sign up, it's free and download it.
https://www.hifiengine.com/manual_library/yamaha/rx-v2400.shtml


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