Front right speaker started with some noise a few weeks ago..only when no music was playing I could hear some slight electrical/crackling noise. It still sounded fine when played loud. Now the channel has fallen to heavy distortion. All other channels operate normally ( FL RR RL and SUB)
My diagnostic is as follows. DC voltage found on bad channel (about 0.8V), all others measure 0 volts. Someone told me to measure voltage on the outside legs of the mosfets/transistors. All measure 0.36V except for one on the bad channel, it measures zero. Does this sound like a bad transistor? It uses combination of two transistors on each channel, the bad one being a K D998 0302.
for now I have tested the resistance of the speakers in the car, all check out at about 4.5 ohm. I doubled the fronts and rears on the same channels, but I feel it runs too hot now even though it is a 2 ohm stable amp.
My diagnostic is as follows. DC voltage found on bad channel (about 0.8V), all others measure 0 volts. Someone told me to measure voltage on the outside legs of the mosfets/transistors. All measure 0.36V except for one on the bad channel, it measures zero. Does this sound like a bad transistor? It uses combination of two transistors on each channel, the bad one being a K D998 0302.
for now I have tested the resistance of the speakers in the car, all check out at about 4.5 ohm. I doubled the fronts and rears on the same channels, but I feel it runs too hot now even though it is a 2 ohm stable amp.
With no power applied, you should not read anything near 0 ohms between the terminal of any individual transistor.
Resistance is more reliable than voltage readings. 0v could mean it's shorted or that it simply has no voltage supplied to it.
Resistance is more reliable than voltage readings. 0v could mean it's shorted or that it simply has no voltage supplied to it.
if it were completely shorted would the channel not be completely dead, or go into protect mode? I'm not very savvy with diagnosis, but why would the distorted channel read 0 volts when powered up?
Shorted 1-3 isn't as bad as shorted 2-3. The former can cause distortion. The latter causes the amp to go into protect or causes the amp to draw excessive current.
it appears each channel has 2 transistors, K D998 and a K D778. Should I take a shot and replace the abnormal 998 on the bad channel?
What is the exact model number?
Did you check the resistance and find that it read 0 ohms from 1-3?
I'd replace both in that channel. The driver transistors may be damaged as well.
I'd replace both output transistors in that channel if one failed. it may be difficult to find the originals from a reliable source. The FJA4213 and FJA4313 are generally good substitutes.
Did you check the resistance and find that it read 0 ohms from 1-3?
I'd replace both in that channel. The driver transistors may be damaged as well.
I'd replace both output transistors in that channel if one failed. it may be difficult to find the originals from a reliable source. The FJA4213 and FJA4313 are generally good substitutes.
well, I contacted JBL (harman) and they agreed to send me a refurbished unit even though it is outside the 1 year warranty. I also contacted the online retailer I got it from, they cannot replace it because its no longer stocked, but they advertised a 2 year warranty so it can be repaired through them. I am going direct to manufacturer as I would think this would be the fastest replacement.
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