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cooked resistors

moebuster said:
doesn't the schematic show 2 10 Ohm?
Click to expand...

No, it shows R3 as 20 ohms @ 10W rating. It doesn't indicate how the 20 ohms is obtained other than with something having 10W rated dissipation.

I think the two resistors you have are someone else's (incorrect) handiwork.

Myself, I'd probably rewire them in series and put them back in. They don't look heat damaged at all, and 5.2 ohms would be expected from two 10 ohm resistors in parallel. Putting them in series should give you 20 watts dissipation capability.
 
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what is in the other speaker ?
i agree they do appear to be incorrect values .. i would expect less heat though .
check the other resistors ..they look the same so may have been changed
 
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petehall347 said:
what is in the other speaker ?
i agree they do appear to be incorrect values .. i would expect less heat though .
check the other resistors ..they look the same so may have been changed
Click to expand...

I think the damage was done previously and what you see is an ill attempt at fixing it. IMO, the scorch mark resembles that of a single resistor moreso than of those two side by side.
 
Board looks cooked but not the resistor? :scratch2: Maybe these have already been replaced previously.

edit: LOL! looks like everyone was thinking the same.
 
moebuster said:
so I got the board out and connected a meter to the resistors and they appear to be in spec-
the two paralled 10 ohm pair read 5.2 ohms.
IMG_1742xs_zpshurdfphx.jpg
Click to expand...

Were the two resistors that are paired, mounted any closer to the board than the others?
 
I'm rather surprised that any resistors (current or previous) have got quite that hot. I used Jantzen 10W MOX resistors to replace the L-Pads in my NS-1000Ms (mid and treble) and they don't even get warm even with heavy use. Perhaps i'm just not driving them hard enough!
 
glen65 said:
Were the two resistors that are paired, mounted any closer to the board than the others?
Click to expand...

they were in the space you see above them and not really to answer the query about the air gap.

I need to dig out another L-96 and compare.
 
this pic is from another pair of 96's I have so it would appear that somewhere in the past there was some monkey business-
IMG_1749f_zpsgpercqv7.jpg
 
so- do I need a 20 ohm at 10 watt resistor?



whoaru99 said:
No, it shows R3 as 20 ohms @ 10W rating. It doesn't indicate how the 20 ohms is obtained other than with something having 10W rated dissipation.

I think the two resistors you have are someone else's (incorrect) handiwork.

Myself, I'd probably rewire them in series and put them back in. They don't look heat damaged at all, and 5.2 ohms would be expected from two 10 ohm resistors in parallel. Putting them in series should give you 20 watts dissipation capability.
Click to expand...
 
the other board-

IMG_1751l_zpsb4nz2goz.jpg

IMG_1752o_zpsafcqolar.jpg

yikes-
still having trouble getting my head around just how this happens without frying drivers first.
 
one of the L-pads in one of these has a couple of "detent" sections and probably need attention.looks like the second foilcal is going to be coming off!
 
:headscrat I'd love to know how those puppies got smoked. It's almost as if someone got in there and did something deliberately...weird.
Is it possible JBL got a bad batch of resistors that just happened to wind up in there?
 
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