Replacing Rail Capacitors

[Bruce Graham]

Hi All;

I am at the beginning of replacing the "Rail Capacitors" on my older d8b consoles. Three (3) of them.

For clarity, I believe the ones in questions are 0.1uf, 25volt SMD (Surface Mount Device).

I have read through what I can find about these and have a couple of questions that hopefully someone can answer for me or point me to someone who can.

1- The "SMD" acronym (Surface Mount Device) is not used in the Mackie d8b manual. They call it an SMT (Surface Mount Technology?). Are these the same items?

2- There are many of these capacitors and some are not on the 16 volt supply rail. Do they need to be or should they be replaced as well?

3- Are the capacitors in questions only on the Brain Board, or is it all rail capacitors (the ones in question) on all boards? The reason I ask is the documentation that I have read refers to the Brain Board only but does refer to other boards but doesn't mention replacing those.

Thanks
Bruce

[munkustrap]

sorry for the late reply but maybe others are interested in that. therfor the answers more than half a year later.

SMD and SMT is the same for me, there are different sizes for SMD 0603, ....

the main troublemakers are the three caps on the brainboard (on the ADC).
why: blocking or rail caps are used to block high frequency pulses/disturbances away from the device. In Special the ADC is critical to those Peaks, as it runs with a clock and all faders/vpots are converted by this one ADC. They are switched through one by one in a high frequency. Spikes(Peaks can disturb the converstion and lead to wring digital values or bit Flips.
Same for all other digitla ICs on the brainboard, but they are more robust to that.

The blocking/rail caps on the other stuff are mainly for the OP-Amps in the Audio path. So if you have a deep Problem here you will hear it on your Speakers.

hopefully that describes everything

[Bruce Graham]

Thanks munkustrap;

Yes it explains things well enough for me.

I will start on the Brainboard.

Cheers
Bruce From Canada