|Created||March 21, 2023|
|Last modified||April 25, 2023|
A simple schematic for your DOD 1222XL mixer.
A friend of mine that owned this mixer. Made in the mid 1990s & that DOD no longer exists I could find nothing as far as a schematic or service manual anywhere.I decided to make up a schematic to work with to make things easier for troubleshooting. The initial complaint was that this DOD was DOA! It turns out that he supplied an AC/DC power adapter with the mixer. The power LED on the main PCB lit up but nothing else worked so imagine my surprise when I opened it up & saw all these diodes & large electro-caps.It's a fairly simple bi-polar (+/- 15VDC) for all of the op amps but there are no buck or boost converters, just some general purpose linear 7815 & 7915s (insulated TO220FP cases). It didn't take long to see that incoming power was supposed to be an AC transformer that plugged in with a 2 pole barrel jack. Once I got that straightened out (with 10-12 VAC & 2A min) everything lit up as it should. The positive half of the AC cycle is filtered & sent to the 7815 while the negative half is filtered & sent to the 7915 regulator. A word of caution here is that if any regulators are to be replaced they must be the plastic covered case as their tabs are mounted to a steel heatsink. The heatsink is secured to the mixer chassis which becomes the circuit common for the whole mixer.The power plug mounted in the power supply & its center male pin (mates with the xfmr barrel jack) is also the circuit common. The DC power is exported to the main mixer PCB via a 5 conductor ribbon cable. This should work for you & good luck!
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