sweetbeats
Reel deep thoughts...
No extender card - I could fab one I'm sure.
No pink noise generator - but I'm sure I could run one off a computer and feed it into the MS-16 so no issue there.
I do have a scope meter - Fluke 123.
You may need to fab that extender card or even a set of extender cables.
If you can get your hands on some sort of audio generator software it would help.
Fluke 123, nice. Okay.
So we know recorded signal is getting to tape full-spectrum. We know that audio reproduced from tape (from either the repro or sync heads, correct?) is vastly diminished below 300Hz. Question (and maybe you answered this already): what happens if you monitor a full-spectrum input at the output (source set to "INPUT")? Is it diminished below 300Hz?
Just out of curiosity, what led you to change out C14 and the R203 (Repro EQ Low) pot? Just curious.