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Old 3rd September 2009, 02:14 PM   #1
smitzk is offline smitzk  United States
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Default help figuring out the rating

A few days ago my bands PA blew at practice and kept blowing fuses. I took it apart and I found a Metal Oxide Varistor (MOV) was fried, or at least I think its a MOV. I took the part out and there aren't very many marking on it. The only thing it says is 'TL08' and below that '020'. I took it to a local part store and they said it was a varistor and gave me a replacement but said they weren't sure if they were the same rating; why they didn't check that I have no idea. Does anyone know of any website I can go to to check this? I can't test the part because the one is fried so I need to find out the rating from a data sheet.
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Old 4th September 2009, 08:23 PM   #2
mjf is offline mjf  Austria
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[ The only thing it says is 'TL08' and below that '020'. I took it to a local part store and they said it was a varistor and gave me a replacement but said they weren't sure if they were the same rating; why they didn't check that I have no idea. Does anyone know of any website I can go to to check this? I can't test the part because the one is fried so I need to find out the rating from a data sheet.[/QUOTE]

hello.
can you make a foto of the bad part?
where was it built in (at the primary side of the transformer,....or secondaries........or.......)?
greetings..........
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Old 6th September 2009, 08:22 PM   #3
smitzk is offline smitzk  United States
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The first image is the part. I know its chipped because when I saw it fry a spark shot out of it and it melted some of it so it became brittle.
The second image is where it is on the board the empty spot with the resistor symbol.
Third image is more of a wide view where it is on the board.
Fourth image is the whole board itself.
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File Type: jpg Image0025.jpg (87.4 KB, 61 views)
File Type: jpg Image0026.jpg (109.0 KB, 60 views)
File Type: jpg Image0027.jpg (116.9 KB, 58 views)
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Old 7th September 2009, 08:34 AM   #4
Elvee is offline Elvee  Belgium
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In my opinion, this is rather a NTC limiting the charging current of the the filter caps:
http://www.gesensing.com/downloads/d...s/920_325a.pdf
It is easy to know which category it belongs: if it's in series, , it is a NTC. If it's in parallel, it is a MOV.
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Old 7th September 2009, 11:02 AM   #5
pjp is offline pjp  India
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If your photographs weren't so awful...
You should take the part out in direct afternoon sunlight and photograph it there. Smaller aperture = greater depth of field.

It appears the damaged part is next to a relay, so I'll guess its an NTC for the switch-on surge limiting.
TL08 will be the size: 8mm (your part should measure 9mm diameter)
20 will be the cold resistance.

edit: a bad inrush limiter is not going to blow a fuse. So I guess you have another failed part further down the line.

Last edited by pjp; 7th September 2009 at 11:06 AM.
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Old 7th September 2009, 03:55 PM   #6
smitzk is offline smitzk  United States
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sorry about the pictures...I don't have a camera besides what is on my phone. I will take more in sunlight once these clouds go away.

so if this NTC is bad it wouldn't cause it to blow fuses? see what I did was I plugged the board is as shown in the pictures trying to narrow down where the short could be. when I did that and flipped the power a spark shot out of the NTC. I instantly knew that was a problem but does this mean that something else could be shorting out on the same board?
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Old 7th September 2009, 03:59 PM   #7
smitzk is offline smitzk  United States
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Edit:
I plugged the board in before I took out the NTC.
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Old 8th September 2009, 07:35 AM   #8
Elvee is offline Elvee  Belgium
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The filter caps and/or the rectifier bridge might be shorted, which in turn would destroy the NTC.
Checks those components, and any other you have the means to measure/control.
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Old 8th September 2009, 07:48 AM   #9
pjp is offline pjp  India
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Quote:
Originally Posted by Elvee View Post
if it's in series, , it is a NTC. If it's in parallel, it is a MOV.
This is probably the first thing you should do. (To definitively establish if its an NTC or a MOV.)

Because if its an MOV you'll be off on a wild goose chase checking the bridge and the caps.
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Old 8th September 2009, 03:27 PM   #10
smitzk is offline smitzk  United States
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well on the board itself the part is labeled NTCS1. My guess is it is an NTC. I am still waiting on a reply from the manufacture but that could be who knows how long.
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