Mezmerize DCB1 Building Thread

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Ok, I'll go the lazy way :)
It was doing fine with the ACA, so probably/hopefully will behave with others...
In the meantime, I'll spend the time with mechanics (mounting the pots, heatsinks etc.)... instead of finally take the deep plunge and work on the AVC... which I still feel not confident/thought through.

:worship:
 
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Just another question:
I'm configuring my build with 2 led: a power-indicator, and channel-indicator. This will be done through the second channel of the rotary-switch (just like you laid out in the i-select docs...).
Is there a better way than feeding both leds from the power-indicator-led? Like, feed the pwr-indicator and channel-indicator-led with its own 2K2 resistor? ...
Thank you again!
 
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Yes, exactly!
Just like this:
 

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diyAudio Chief Moderator
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The 2k2 power LED feeder resistor on the DCB1 pcb gets voltage from the local 7812 reg rail. The input position LEDs if engaged are fed voltage from the 7812 reg on the I-Select pcb. Better don't use a common power on LED's feed and input position LEDs feed. Just adjust the 2k2 power LED limiting resistor value for equal brightness with the input position indicator LEDs.
 
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Dear Salas

I'm not sure wether I'm good:
DCB1 turn on, all LEDs are lit.
Can't hear the relays on power-on, switching channels is good, and some 3 seconds after turning it off it clearly clicks

I first measured a DC-offset 1.1VDC and 0.7VDC (*), but now—after a few measurement at TP / across the 18r it's 0.00 and doesn't move...

I'm measuring at TP 9.75V / 9.82V
Voltage drop at 18r 1.67V / 1.35V
...
What do you think?

*) [EDIT: I am really not sure about the DC-offset I was able to measure, as my first thinking was "a little highish but still ok", but I didn't write it down]
 

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Last edited:
diyAudio Chief Moderator
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DC offset you measure at each signal output RCA between center and barrel. It must not be more than 5mV is our spec. Use the DCmV range of your meter.
Rails look good nearing the 10V goal and close enough together. Drops across each 18R parallel pair suggest 185mA and 150mA i.e. certainly more than enough spare current is created in the master constant current sources.
To check if the output relay does its job see whether a couple of seconds are passing until DC offset appears i.e. it engages with a delay after power on. Since inputs are selected the other relays surely do their job.
 
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Joined 2017
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Dear Salas

I'm not sure wether I'm good:
DCB1 turn on, all LEDs are lit.
Can't hear the relays on power-on, switching channels is good, and some 3 seconds after turning it off it clearly clicks

I first measured a DC-offset 1.1VDC and 0.7VDC (*), but now—after a few measurement at TP / across the 18r it's 0.00 and doesn't move...

I'm measuring at TP 9.75V / 9.82V
Voltage drop at 18r 1.67V / 1.35V
...
What do you think?

*) [EDIT: I am really not sure about the DC-offset I was able to measure, as my first thinking was "a little highish but still ok", but I didn't write it down]
I repeated the measurements today, but with the uotput-wire disconnected:
Offset is
R ≈ 1.5mV
L ≈ 0.4mV
So it looks the switch or the connection switch to plugs is fishy (it was a struggle and it’s continuities are weird. Removing this now)

Here’s the drawing for the front-plate just because I like its „proportions study“ :)
 

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