Sometime ago the white smd leds that works as dB signage of my mastering AD/DA converter start to burn out. When only some few remains from 32, I decided to replace them.
I got the smd leds values from a source and found an equivalent, due the original part is not in production anymore.
I checked polarity and I was a bit confused at the beginning, but proceeded with soldering. When tested the unit, all leds, included the VU ones (green-yellow-red) lit without any sound signal. Not full bright but enough to realize something was not ok. Needed to buy a mignifier glass and analyzed the circuit with a better eye, and understood that I need to solder the leds the other way around. Desoldered all, and the white leds shine better, and the VU leds lit barely standing still. Injected signal and for my surprise the white leds lit but instead of permanently lit from 40dB to 0dB as it should, they act as an inverted VU, that saying that depending on the decibels the VU leds lit and increase in the scale, these white leds turn off in sync. Exactly as a negative mirror of the VU.
I asked for the schematics to the manufacturer of the unit, but they stated that disclosing schematics is forbidden. So I draw one myself the best I could.
Can you guys help me find out?
I got the smd leds values from a source and found an equivalent, due the original part is not in production anymore.
I checked polarity and I was a bit confused at the beginning, but proceeded with soldering. When tested the unit, all leds, included the VU ones (green-yellow-red) lit without any sound signal. Not full bright but enough to realize something was not ok. Needed to buy a mignifier glass and analyzed the circuit with a better eye, and understood that I need to solder the leds the other way around. Desoldered all, and the white leds shine better, and the VU leds lit barely standing still. Injected signal and for my surprise the white leds lit but instead of permanently lit from 40dB to 0dB as it should, they act as an inverted VU, that saying that depending on the decibels the VU leds lit and increase in the scale, these white leds turn off in sync. Exactly as a negative mirror of the VU.
I asked for the schematics to the manufacturer of the unit, but they stated that disclosing schematics is forbidden. So I draw one myself the best I could.
Can you guys help me find out?
Attachments
You probably had them the right way round the first time, but you used LEDs with too low a Vf so they came on before they should.
Are the new LEDs more efficient than the old ones? Oldschool LEDs were barely visible when checked with my Fluke 77 on the diode test range, but modern ones light brightly.
