Old Amplifier reeks a burned smell and smokes after being turned on

Thread Starter

CobraL0rd

Joined Jan 18, 2017
42
My mom has an old ~40 year old audio amplifier LUXMAN L-210, that hasn't been turned on for about a decade.
I found some time the other day and turned it on to see whether it's working and how it's performing.
So it did turn on and seemed to work (I have radio tuner, cassette player and disk player peripherals running as well).
I didn't stress test it or anything.
However soon after, about ~3 minutes after turning it on I noticed a very bad smell.
After about 10 minutes slight smoke was billowing.
So I tracked it down, localized the issue and it was the amplifier.
At first I thought it was a problem with the transformer.
But if that was the problem it wouldn't be running at all right?
At any rate, I opened up the cage and first off I dusted it off, it was a mess.
I plugged it in again and watched as it was operating all alone (no other peripherals attached).
True enough the smell was apparent almost immediately.
I have a laser thermometer and I run it across all the parts (at least every one I could) and noticed the temperature on all of them.
So everything was fine, room temperature, except a single capacitor which was reaching 150 degrees Celsius after 10 minutes of operation and slowly growing!
After leaving it on for about 20 minutes no smoke had come out though and I realized the smoke was due to the huge amount of dust that must have been burning up around the capacitor and as such causing it.
The circuits and components next to it were also at high temperature (highest was ~40 max) but I think this was just the heat buildup from that single capacitor.
You can see what capacitor I'm telling you about in image No1 (amp_luxman_1_.JPG).
It's located around the middle, It's greenish, just above two fuses and to the left of two smaller greenish caps and another huge cap. I made a black mark/dots with a marker on top of it (you can't miss it).

So my question is, can I conclude that this capacitor is the sole problem of this setup?
Would it be enough if I replaced it with another same capacitance capacitor? I have a multimeter that tests capacitance, I could check it out. My soldering skills are rusty but I'll give it a go.
Can you spot other problems or do you suspect something else to be out of place?
Any suggestions and thoughts are welcome.
 

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AlbertHall

Joined Jun 4, 2014
11,309
Yes, this is the sort of thing that electrolytic capacitors do, especially after a period without being used.
BUT that component looks more like a resistor to me. Does it have any readable markings or coulour bands on it?
 

schmitt trigger

Joined Jul 12, 2010
438
If the only troubleshooting information you can provide are photos, then you should really take good pictures.

“Good” meaning focused, properly lit, high resolution, close-up and un-blurred images.
 

MrChips

Joined Oct 2, 2009
23,515
With very old equipment the first thing for you to do is to remove the cover and vacuum out the dust. Too late for that.
The next thing to do is apply power and look and smell. Too late for that too.

I would go ahead and replace the capacitor, assuming it is a capacitor.
If it is a power resistor then yes, you were burning off the dust that settled on the amplifier. Clean out the dust with a brush and vacuum.
 

djsfantasi

Joined Apr 11, 2010
7,689
I’d remove the suspect component. Try removing just one end first. It looks like there are identifying marks on the reverse, and once it’s free from the PCB, see if you can read the marks and post them here. Include a clear, focused picture of the marks if you can.*

Note *: What did you take the picture with? On an iPhone, before taking the picture, you can tap on the desired object and the phone will automatically adjust lighting and focus of the object. This may work with other phones.
 

atferrari

Joined Jan 6, 2004
4,322
If the only troubleshooting information you can provide are photos, then you should really take good pictures.
“Good” meaning focused, properly lit, high resolution, close-up and un-blurred images.
With daylight but no sun light shining directly on it.
Make many, a bunch, and then select the best ones.
 

Thread Starter

CobraL0rd

Joined Jan 18, 2017
42
Yes, this is the sort of thing that electrolytic capacitors do, especially after a period without being used.
BUT that component looks more like a resistor to me. Does it have any readable markings or coulour bands on it?
Thanks for response. You were right. It's a power resistor. I was hasty didn't even notice. I measured resistance to around ~300 Ohms. It has no color bands but by closer inspection I was surprised to see that the resistors have their resistance value as well as tolerance written on top. On most of the other resistors it's clearly visible but this one not that much. I did make out the "3[2|3?]0" numbers though. Anyway. I looked at the schematic but its so worn off I can't see a thing. So what does it mean that the resistance value is almost nominal. If it was malfunctioning shouldn't its resistance been very low or very high and very fluctuating. By measuring the nearby resistors I did notice that their resistance value was not fluctuating however this one was with values ranging from 280 to 400Ohms. I suppose that is a sign that its quality is fading right? So basically what I have to do now is order a new one? Resistors are cheap, but what I'm worried about is:

1. brushing up my soldering skills but oh well I'll do it
2. whether the problem lies with another component and it's transferring to that one resistor instead. Probably I'm overworried about it I know..
 

AlbertHall

Joined Jun 4, 2014
11,309
Resistors only exceedingly rarely burn up because of a fault with the resistor. It is much motr likely that some other fault is overloading the resistor so replacing the resistor will just result in another burnt resistor. I would be leaving the resitor alone and be trying to find the main fault. That is going to be difficult without a schematic to work from.
 
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