Capacitor overheating

Thread Starter

luckycatt

Joined May 15, 2024
8
Hi! im kinda new to electronics, currently studying automation engineering

I've got an old pedal board for my guitar, and it used to work fine, but after it was left unused it just wont turn on, so i opened it up and discovered that a resistor (18 Ω 5%) is getting really hot, and the pedal board isn't even turning on, so i wanted to come here and see if i could learn more about this and maybe even fix it up myself

I'll attach an image pointing to the capacitor in questionWhatsApp Image 2024-05-15 at 8.42.27 PM.jpeg
 

Thread Starter

luckycatt

Joined May 15, 2024
8
Hi! im kinda new to electronics, currently studying automation engineering

I've got an old pedal board for my guitar, and it used to work fine, but after it was left unused it just wont turn on, so i opened it up and discovered that a resistor (18 Ω 5%) is getting really hot, and the pedal board isn't even turning on, so i wanted to come here and see if i could learn more about this and maybe even fix it up myself

I'll attach an image pointing to the capacitor in questionView attachment 322414
i thought so too, but looks like the other side is very well soldered
 

dovo

Joined Dec 12, 2019
72
That is a resistor, not a capacitor. The resistor shows no signs of being too hot and the board doesn't either because it is not discolored. It does look like the solder pad has been pulled off. Did someone repair that location at some time?
 

MrChips

Joined Oct 2, 2009
31,076
R54 is a resistor, not a capacitor. It was anticipated that it would dissipate a lot of power. That is why they specified 18Ω 2W resistor.

Before jumping the gun, you need to get out your DVM and take some voltage measurements. There are ample test points on the board. Measure the voltages at TP14, TP16, TP27, TP30, TP19.
 

Thread Starter

luckycatt

Joined May 15, 2024
8
That is a resistor, not a capacitor. The resistor shows no signs of being too hot and the board doesn't either because it is not discolored. It does look like the solder pad has been pulled off. Did someone repair that location at some time?
I'm sorry for the misinformation, indeed it is a resistor, but I don't think there were any repairs made, also I apologize for the late reply.
 

Thread Starter

luckycatt

Joined May 15, 2024
8
R54 is a resistor, not a capacitor. It was anticipated that it would dissipate a lot of power. That is why they specified 18Ω 2W resistor.

Before jumping the gun, you need to get out your DVM and take some voltage measurements. There are ample test points on the board. Measure the voltages at TP14, TP16, TP27, TP30, TP19.
R54 is a resistor, not a capacitor. It was anticipated that it would dissipate a lot of power. That is why they specified 18Ω 2W resistor.

Before jumping the gun, you need to get out your DVM and take some voltage measurements. There are ample test points on the board. Measure the voltages at TP14, TP16, TP27, TP30, TP19.
I will try testing the voltage, but seeing as this is a non-trivial problem I don't think I will be able to do this with the tools I have at my disposal.
 

Ian0

Joined Aug 7, 2020
10,269
Just a thought. . .
Is the supply you are using the correct polarity?
Most guitar pedals (though not all) have the centre pin negative.
Most power supplies have the centre pin positive.
If the resistor and a reverse-diode form a reverse polarity protection circuit, then the resistor will get hot.
 

MrChips

Joined Oct 2, 2009
31,076
If you have a basic voltmeter we can guide you through with trouble-shooting step-by-step. I will post the schematics when you are ready.
 

Thread Starter

luckycatt

Joined May 15, 2024
8
Just a thought. . .
Is the supply you are using the correct polarity?
Most guitar pedals (though not all) have the centre pin negative.
Most power supplies have the centre pin positive.
If the resistor and a reverse-diode form a reverse polarity protection circuit, then the resistor will get hot.
Yes, it's the same power supply I used previously with this pedal (9V 3A) also, I'm positive that the polarity is correct.
 

MrChips

Joined Oct 2, 2009
31,076
I got my DVM, I'm going to plug the pedalboard and measure each test pad to a common ground, correct?
There are a large number of test points. Don’t do them all. Let’s do them in a methodical functional order.

I will post the schematics so that you can learn something from the experience.
 

MrChips

Joined Oct 2, 2009
31,076
Here is a clearer diagram of the power input circuit (click on the diagram for a larger view).
TP30 and TP19 should both be at +3.3VDC.

G1X Power Input.jpg
 
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