Well, no, if you are measuring on the LED itself. The presence of R218 indicates the LED is a classic LED without internal resistor.
BTW, you are working on the tailight of an auto that doesn't run. Not very productive. Replacing the bad LED first will not keep this amp out of the trash can. As an auto that won't run goes to the scrap yard whether the taillight works or not.
You need to be checking points like collector of Q317 & emitter of Q319 to make sure they are somewhere near speaker ground and no more than 4.2 v apart. That is with the output transistors removed and the light bulb in series with the AC cord. Also with the input shorted.
Your assertation that "the output transistors are bad" might be correct, if the CE and BE junctions of those fail the .6 v forwards ---- backwards (open) diode test. A more stringent output transistor test is reverse Ice with base open is microamps with the junction back biased by 7 to 12 v dc. This is a Vceo test. Stressed output transistors sometimes pass the 2v DVM diode test and fail the Vceo test. I use the milliamp function of a DVM for this test, series a 12 v wall power supply series a 47k resistor to prevent avalanche. A wire with that source voltage and supply resistance would measure 255 microamps. Good transistors should measure a lot less current.
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Hello.
I replaced the output transistots, amplifier works fine.
Thank you.
But the question of dead red led is open.
I replaced the output transistots, amplifier works fine.
Thank you.
But the question of dead red led is open.
Congratulations on a working amp.
Well, if the protection led is dead, change it.
Of course if you are measuring the too high voltage at Q205 and R218 then a dirty contact on JP205 connector could cause the high voltage. In that case remove and replace JP205 to scrape any oxide off.
The plus of a new led is the long lead. Red Led's can usually be salvaged instead of bought. LED won't read on a dvm but the numbers will usually blink a reading one time before going to ---- when the red probe is on the plus lead.
Well, if the protection led is dead, change it.
Of course if you are measuring the too high voltage at Q205 and R218 then a dirty contact on JP205 connector could cause the high voltage. In that case remove and replace JP205 to scrape any oxide off.
The plus of a new led is the long lead. Red Led's can usually be salvaged instead of bought. LED won't read on a dvm but the numbers will usually blink a reading one time before going to ---- when the red probe is on the plus lead.