Yamaha Speaker Connection

[sebby]

Hi all,
I've really enjoyed looking at this forum in recent months while shopping around for a 70s stereo receiver as an upgrade from the 90s Kenwood I've been using for years.
For background, I am totally inexperienced with electrical repair.


Last week I bought a Yamaha CR-450 for 70$ from a thrift store, probably cheaper because the power line in had been severed. I soldered a new one in and last night got it working fine, as you can see in this pic it's on Speakers B and playing FM radio beautifully. I then rotated the piece sideways to screw the case back on at the bottom, and when I put it back down I could not get it to work again. It powers on fine and I can hear from a tiny sound inside that it is still getting FM signal, etc. I'm sure if I could find my headphone jack adapter it would play fine through the phones slot. My speaker wire still works on my other stereo.

As such, I'm pretty sure the connections to the terminal for the speaker wire got messed up somehow. I have no idea how, since I was not rough with the equipment at any point, but I can't see what else would be wrong. So, I'm hoping someone with more experience than me can look at these pictures and tell me if I should replace the terminals, and if so with what part, or if there's some more obvious fix I'm missing. I tried both terminals A + B, a mix of both, swapped left to right, etc.

Thank you in advance for your expertise, and I wish I could contribute something more useful here before asking for help. Maybe someday.

Sebastian

 

[ivandezande]

I really don't think there's anything wrong with the speaker terminals. It's wire....not much to go wrong.

Also A and B speakers go the exact same place. It's a two channel unit, not four.

Is it coming out of protection? Why is the fuse holder and the antenna connectors just dangling? What's with the blue tape?

 

[sebby]

Also A and B speakers go the exact same place. It's a two channel unit, not four.

I figured this much out. The A unit has one switch that doesn't open all the way, which is why I'm using B.

Is it coming out of protection? Why is the fuse holder and the antenna connectors just dangling? What's with the blue tape?

I'm afraid I don't know what you mean by the first part. I have tried maneuvering the fuse holder around, but it seems to want to hang right where it is based on tensions in the wires. I tightened up the antenna connectors to the back plate too.
Blue tape is gone now, relic of my power line replacement.

 

[spark1]

That unit has a protection relay, which should close shortly after the unit is powered up. You should hear it click when it closes. If not, try powering it up without the speakers connected.

The fuse holder is supposed to be mounted to the back panel. If not, it could short out to the chassis or another component while "floating" around.

Check that fuse, and the four fuses next to the big gray filter capacitors.

The relay is in the little clear plastic box next to the filter capacitors. It would be interesting to see its solder connections; you will have to remove the bottom panel to get a pic.

A clipped power wire is sometimes indicative of a unit determined to be not worth fixing, although sometimes it is done when a unit is dropped off at an electronics recycling facility (regardless of its operating status).

 

[sebby]

That unit has a protection relay, which should close shortly after the unit is powered up. You should hear it click when it closes.

The fuse holder is supposed to be mounted to the back panel. If not, it could short out to the chassis or another component while "floating" around.

Check that fuse, and the four fuses next to the big gray filter capacitors.

Hi, thanks for the explanation. I don't think I'm hearing a click, just a moment of silence and then the hissing (FM static playing very quietly inside the machine) starts.
Is there any way to reset that so that it will come out of protection?

Ok, I've mounted the fuse holder to the back again, I see now how it fits.
What should I be checking for? Should the fuses light up or something? Sorry again for my inexperience.

 

[spark1]

The best way to check a fuse is with a multimeter.

You can do a visual inspection to see if the filament (the fine wire inside the fuse, connecting one side to the other) is broken, and/or if the glass is cloudy or charred on the inside. Also, verify that they are of the correct amperage rating (it will be marked on one end of the fuse). The correct value should be on a tag or printed on the board in the unit.

The hissing sound is not likely to be radio static, since there is no speaker inside the unit to make sound. More likely to be a problematic electrical connection. Are you sure it is not coming from the power switch?

After checking fuses, disconnect speakers and try powering it up (assuming fuses are good).

 

[sebby]

I see... It looks to me that one of the filaments in the 4 parallel fuses is totally broken and another has a char in the middle of it.
I'm not sure why the receiver was working so beautifully last night, if I hadn't taken a video I would think I was imagining it. I'm guessing I need to replace these?

 

[spark1]

I would guess that they failed due to a short circuit resulting from fuse holder shorting out to the chassis, in turn occurring because it rested on the chassis after turning the unit on its side. If so, having the holder stabilized may resolve the issue. However, I suspect that there is another, deeper problem....as evidenced by someone removing the fuse holder in the first place.

Yes, the fuses must be replaced. If they blow again, the problem is definitely deeper. Don't replace them a second time until the underlying problem is addressed.

You will want to use fast-blow fuses with same amperage rating and equal or higher voltage rating. You can probably get them at a traditional hardware store. Make sure they are same physical size.

 

[sebby]

Thanks, I really appreciate it. That sounds like a reasonable explanation to me, except the part about the fuse holder being loose - I realized that was just something I had done while unnecessarily removing the back panel while trying to remove the unit from its case.
I'll try replacing those fuses and see what happens.

 

[cademan]

It could also have been a freak short when you put the bottom plate back on or the screws could have bit into a stray or close wire hanging too close to the plate and/or screws.

 

[spark1]

Thanks, I really appreciate it. That sounds like a reasonable explanation to me, except the part about the fuse holder being loose - I realized that was just something I had done while unnecessarily removing the back panel while trying to remove the unit from its case.
I'll try replacing those fuses and see what happens.

What part of my guess-splanation do you find unreasonable?

The loose fuse holder could have easily come into contact with something and caused a short circuit.

There are of course a wide range of other possibilities, but to me it makes sense to start with the most obvious, given the data at hand.

Have you assured that the power switch is not the source of the sizzling sound?

And now that we know you removed the back panel, or attempted to do so. it does raise the issue of damaged connections.