250W KRK 10s Active Sub Monitor Unable to Power On despite Intact Fuses

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You can check that your meter is working by connecting the leads together. It show show near zero or beep or both. With the leads apart, it should show overload somehow. A blown thermal fuse will be an open circuit, and the meter will behave like the leads are apart. A good thermal fuse will behave like the meter leads shorted together.

Just buy the thermal fuse. Measure the new one and compare with the old one. If they are the same, you've wasted $2.90. If not, then replace the thermal fuse, or get someone who knows how to solder to do it.

Make sure that you disconnect the mains lead before any of that.
 
Yes there was more than 1k (10k?) ohm's of resistance on high ohm settings and infinite resistance on low settings, so that would mean that the circuit is broken? there was still a measurable amount though, but obviously not a lot. If I'm supposed to get a strong connection of like 10 ohm's then that's not the case in this situation.
To clarify, the reading was taken from the left and right prongs on the ac power input with the switch in the on position.

I'm honestly pretty proud of myself for getting this far with the help of this forum. I'm going to buy a soldering gun... I got this.. I will experiment on other things a bit first hah
 
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There are thousands of types of multimeter. I don't know which one you have, or what the readings mean without seeing it.

It sounds like it is the fuse, but to make sure, could you post pictures of the meter in the following conditions:-
1) low Ohms, no connection
2) low Ohms, meter leads connected together
3) low Ohms, meter leads connected left and right prongs of power lead with the switch on, selector set to 110 V
4) low Ohms, meter leads connected left and right prongs of power lead with the switch on, selector set to 240 V
5) high Ohms, no connection
6) high Ohms, meter leads connected together
7) high Ohms, meter leads connected left and right prongs of power lead with the switch on, selector set to 110 V
8) high Ohms, meter leads connected left and right prongs of power lead with the switch on, selector set to 240 V

(please make sure you say which photo is which)

and make sure you don't touch the meter leads, especially in the high Ohms range, as many meters will measure your body resistance.
 

this should cover everything better than photos would. Im quite exhaused and am done testing for today but will be back tomorrow to continue if this isnt conclusive
 
I'm a little concerned about opening the plastic insulation on the transformer to get at the fuse. it appears to be right on the outside of the coil, i guess i wont know till I crack it open..
 
Wow. An analogue meter. I haven't used one of those for 30 years.

Anyhow, it seems clear that there's no connection in the subwoofer in any condition, and it does look like the meter works fine. The tiny bit of defection on the meter could be the capacitors on the input charging up. It's not important.

You might be able to get away without opening up the transformer. Can you get to the wires marked with the arrows on this?

If you can, you just connect the new thermal fuse between those two points, and fix the thermal fuse to the outside of the transformer. Leave the old one where it is.

Just make sure you have the correct fuse in place. If you've wired it up wrong, that would most likely protect you transformer.

Once you have the new thermal fuse in place, run tests 3, 4, 7 and 8, so and show us the results.
 
I am late to the discussion, but looking at your pictures and video, there may be a fuse hiding in the mains connector.

Look at this one:



There is a little drawer on the front, which can be opened up by levering it GENTLY with a screwdriver:


A little drawer will pop open to reveal a fuse:


This connector of mine has two fuses, one is there as a spare.
(I cannot remember ever seeing two fuses in one of these things before).

If you have a fuse in there, check to see if it is blown.

JimB
 
I'm not going to lie, I don't trust myself enough yet not to destroy the very valuable to me piece of machinery by bridging power connectors. I think I would feel more comfortable at this point making an incision, replacing the fuse, soldering it and taping it. But I really do not know if that will compromise the expensive transformer.

JimB, if you're using the same amp as me I believe that is a misconception and the second fuse is for the 240v power. One of them is 3A, one is 4A. I read that in the manual but it always gets called a spare and KRK has never corrected that so beats me *shrugs*
 
I am not using any amp, the connector in the picture is just something out of my "parts archive" which I am using to show the fuse drawer.

Does your mains connector have that drawer, and is the fuse OK?
That is all that I am saying.

If the fuse in the mains connector is blown, then the thermal fuse may be OK, save you doing "wiring butchery".

JimB
 
they're good, checked both of them. The evidence appears to be pretty strong that its the thermal fuse, i haven't tested any connections beyond that point but since we found the short, i dont believe that is necessary?
 
As long as the transformer itself has not failed & it just temporarily got too hot, it will probably be possible to get to the fuse by removing some insulation on the transformer.

Just be careful not to let anything dig in to the windings while taking the insulation off.
 
Fix the thermal fuse and hope for the best!

It's almost certainly OK, that's what the thermal fuse is for - to stop it self-destructing..
 
Transformers like that usually only fail by overheating, and then you can see and smell the burned insulation.

You can also test that the windings conduct electricity. The primary will be around 10 Ohms. That is very approximate. The secondary windings will have a very low resistance. It will be too low for your meter to measure, and it will read the same as putting the leads together.
 
I've got a week to wait till the fuse gets here. I'll have a status update on Hamboo then and If there's anything else you think I should do in the meantime I'll still be online. thanks everyone for the help.
 
i got the fuse, openmed the transformer, its really hard to find, coated with as metal sheith and layered upon layers of plastic
.
 
I don't think it's ruined. However you should stop trying to remove the old thermal fuse. Just work out which wire is which and connect the new thermal fuse between the appropriate wires. Look at my post #28
 
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