68kMLA Classic Interface

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Classic II bomarc audio schematics
Posted by: marcelv on 2023-02-20 14:13:40 Can someone confirm the bomarc schematic for the classic II is wrong regarding pin 1 and 2 of the DFAC? wrong version (pin 1 connected to pin 2 and swapped) corrected version Second question where does the via next to C11 go
Posted by: marcelv on 2023-02-21 00:40:37 checklist I used for the audio repair on the classic II rev A board C3 47uF 16V - gnd + R2, R7, R15 C4 47uF 16V - phones switch + pin 5 U1 C5 10uF 16V - gnd + pin 8 U2 (78L08), R21 C6 10uF 16V - gnd + R6 (4k7 to R15) C7 10uF 16V - gnd + pin 7 U11 , R33 C8 10uF 16V - gnd + pin 3 U1 C9 1uF 50V - pin 10 DFAC + R29 C10 10uF 16V - mic in + pin 3 U11 , R7 C11 10uF 16V - gnd + pin 2 DFAC pin 1 DFAC is connected to R32 , R37 C12 10uF 16V - R35 , U11 pin 6 + pin 6 DFAC , R40 C13 47uF 16V - gnd + pin 1 U12 C14 10uF 16V - gnd + pin 1 U2 (78L08) C15 1uF 50V - pin 12 DFAC + pin 13 DFAC , R37
Posted by: smrieck511 on 2025-05-25 10:55:25 Incredibly helpful. Thank You!
Posted by: btb on 2025-05-25 15:00:29 Having just reverse-engineered the whole thing, I can confirm that error on the DFAC. The via next to C11 doesn't go anywhere, this board is littered with such dead-ends. Presumably test points.
Posted by: smrieck511 on 2025-05-27 16:38:51 Wait...I'm confused. Are we saying the C11+ to DFAC pin 2 on the schematic is incorrect or just that via? Sorry if I'm slow on this...I just double checked the continuity of all the caps...I didn't have continuity from C11+ to DFAC pin 2 (I checked it six times). No visual sign of a broken trace under a microscope. I do have audio but was wondering if it was perhaps a bit low. I ran a bodge wire but curious if anyone knows what that particular break might affect or if that's what we're talking about when we say the schematic is wrong? Should I remove the bodge?
Posted by: JC8080 on 2025-05-27 17:23:03 Wait...I'm confused. Are we saying the C11+ to DFAC pin 2 on the schematic is incorrect or just that via? Sorry if I'm slow on this...I just double checked the continuity of all the caps...I didn't have continuity from C11+ to DFAC pin 2 (I checked it six times). No visual sign of a broken trace under a microscope. I do have audio but was wondering if it was perhaps a bit low. I ran a bodge wire but curious if anyone knows what that particular break might affect or if that's what we're talking about when we say the schematic is wrong? Should I remove the bodge? If you haven't already, look at btbs other post where he links to his redrawn schematics.
Posted by: smrieck511 on 2025-05-27 18:33:24 Should be connected.
Posted by: btb on 2025-05-29 00:05:15 I just double-checked it and yes, it should definitely be connected.
Posted by: smrieck511 on 2025-05-29 08:51:20 I just double-checked it and yes, it should definitely be connected. View attachment 87191 excellent. Thanks.
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