Electronics > Repair
KRK Rokit 5 RPG2 speakers (again)
waste:
shiiiit, you put so much effort to simulate it , I will bring out the oscilloscope and scope the mute pin.
Rokit's only have one channel but it has two amplifiers for twitter and woofer. They both get the same signal to mute but the twitter doesn't make a sound .
I'm bringing out the scope now, and report back (from my multimeter definately the whole oscillation to stable 6V (relative to Vs-) didn't take 4 seconds.
thanks again for the effort
waste:
I bear news :) I scoped the Vs- to the mute pin in 2 different Rokit5 .
The one has the optocoupler and the TL074 limiter on the amplifier board (that's my no pop rokit) , board revision 1.2
And the other one is the one that Pops. It has the limiter with the TL074 on a daughterboard but no optocoupler (does it use the transistors? there is no schematic for this board). Board revision 2.0 , probably they wanted to save money on the optocoupler? even though a seperate daughterboard doesn't sound a cheaper alternative.
Why am I talking about the limiter circuit? Because actually the mute pin behaves on both the same way and totally in spec according to the datasheet so probably the problem is not there. Check on the pictures. And yes your simulation was correct, it actually takes around 4 seconds to turn fully on (at 6V+ relative to Vs-) :)
waste:
As I have to confess I can´t follow how the limiter works, and have no schematics for rokit5 without optocoupler (only rokit 6 with optocoupler) I came across this article
https://windowpaneaudio.wordpress.com/2019/05/09/rokit-5-g3-limiter-and-stand-by-mute-removal/
where it actually states that the limiter circuit works all the time with just a transistor (no optocoupler) so I guess they eliminated the optocoupler in v2.0 and they passed this design on Generation 3 too. So If I get correctly the whole salad of opamps, the limiter limits the LowPass output in ver2.0 using only a transistor, so in my pop rokit the limiter doesn't limit anymore and is always on (dead transistor?). Is this train of thought any good, or am I just fantasizing like an AI?
cte:
Actually, I've never seen or repaired this device before, so without a schematic I will have to look into my crystal ball... :-DD
There might be a component named LCR-0202 on the PCB. Someone said, this was the culprit in his Gen2 device. Maybe this works for you.
Full datasheet: https://電子うさぎ.com/wp-content/uploads/2020/09/lcr0202.pdf
waste:
Thanks that's what the ver 1.2 board has with the optocoupler and the opamp on the board.
The ver 2.0 board unfortunately doesn't feature an optocoupler anymore, so that's why I fantasized that the same job was assigned to a lowly transistor as the guy in the article suggests about the rokit5 generation3 :)
Anyhow I will put the thing to rest for now and attack the issue some other future time.
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