Weird fuses in Pioneer SA-510

[Cr3ator]

After buying an old Pioneer SA-510 from an Ebay like website in Holland, I was very happy to hear some nice music in my room again. After a while the left channel broke down. So, I opened up the amplifier and checked the fuses. Two of them were dead. After replacing both of them, I fired the amp up with an variac to see one fuse die again immediately.

Nevertheless the amp was functioning as expected. All the lights went on, and both channels were playing music again. With one dead fuse, this is not the behaviour you would expect. I replaced this fuse once again, and saw the other one burn out! WTF?? Same thing, the amplifier was functioning. I left it as it was but would really like to know the function of this dual fuse. Anyone who has had the same experience?

See picture for more details on the particular fuses. Arrow indicates dead fuse.

ErikH.

[Netlist]

Maybe their purpose is to protect the AC-voltage outlets on the back of the amplifier.

/Hugo

[Cr3ator]

Originally posted by Netlist
Maybe their purpose is to protect the AC-voltage outlets on the back of the amplifier.

/Hugo

They aren't used, there are no shorts and it's not always the same one that blows if you replace them. But I'll check the outlets.

[Geek]

Speaker Z too low?

[Cr3ator]

Originally posted by Cr3ator


They aren't used, there are no shorts and it's not always the same one that blows if you replace them. But I'll check the outlets.

Checked: All work ok. So what we got is a perfectly working amplifier, but still one fuse missing

[Netlist]

Does the amp still work when you take out both fuses?
Where are the wires that come from the fuses lead to?

Time for a new Signature:
If it's broken and it works...don't fix it.

/Hugo

[Cr3ator]

Originally posted by Netlist
Does the amp still work when you take out both fuses?
Where are the wires that come from the fuses lead to?

Time for a new Signature:
If it's broken and it works...don't fix it.

/Hugo

With both fuses removed the amp doesn't work at all.

I like the signature I think I have to use that one for some time...

[Stocker]

That looks a bit nasty inside. Hit it with some compressed air and see how it does.

[Cr3ator]

Originally posted by Stocker
That looks a bit nasty inside. Hit it with some compressed air and see how it does.

It sure can use some cleaning, but it's a very sticky, grease like substance... Perhaps better leave it there. Even if that causes a short, how can the amp still work??

[raypsi]

I'm retired from Sears, but we used to repair lots of every brand of stereo. Stereo's of modern design used split supplies. the preamp mains would be +15vdc and -15vdc so guess what? They have a fuse for each main, plus and minus. Same goes for the outputs, that run off of split supplies a fuse for the plus and a fuse for the minus supply's

Make sure the fuse clips are clean and tight. Loose clips will cause fuse to overheat and even though you are nowhere near the current rating of the fuse the heat will blow them out.

Let nothing block the air vents on older units as they tend to draw more current with age. Capacitors become leaky, causing the supply to draw more current.