Audio signal tracing & schematic analysis on a Tascam 244 (I was WRONG about magnetic heads!)

I have made two videos about the playback circuit in the Tascam 244 before, but this is a more concise video showing me using the audio probe in a real workbench example, then showing the schematics for the circuit under test.

Spoiler alert - in the end the problem I was having (playback on tracks 2-3 was present but very quiet) wasn't anything to do with the playback circuits!

Instead I stumbled upon a fail condition of the magnetic head I hadn't seen before, that is goo from decomposed rubber in the transport getting ground into and blocking the apertures...or at least that is what I think happened?! I'd need to come across the same problem a few more times before I'm certain, and also find a way to recover a head which has become blocked like this: As I have said in other videos, the heads are pretty much the leats fungible component in these units. Maybe a bath in isopropyl would do the trick?

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CHAPTERS
0:00 Introduction
1:08 Signal tracing the 244's playback circuit with a DIY audio probe & test tape
3:36 Looking at the schematics for the circuit I just traced
8:57 The real cause of the problem- a new magnetic head fail condition!