Hitachi VT-6500A Audio Playback

[ThePlague]

Hello all,

I am currently working on a Hitachi VT-6500A that had all but the loading belts turn to goop. I have replaced the capstan belt, take up reel belt, and pinch roller. I didn't change out the idler wheel as it feels fine and looks to be a pain to replace, though I did manage to find a NOS assembly.

The only belt I wasn't aware of was the counter pulley belt which of course also turned to goop. While I am waiting on a replacement belt, I am trying to determine the source of my issue.

The issue: Video plays back perfectly with all the new rubber, but there is no audio out of the line out, earphone, or RF circuits. I can hear amplifier noise so I don't think that is the issue.
I have been digging through the circuit diagrams and traced the counter/memory switch to the flip-flop circuit that is handling the memory control. One of the outputs of this circuit is OSC STOP. Looking in the service manual, that signal is described as "Stops bias oscillation of audio circuit in modes other than REC, Audio dubbing modes" (when HIGH). This sounds to me that if this signal is high, there will be no playback audio out.

Is it possible that without the counter belt attached, the system is not producing audio? It seems like an odd connection, but it is all I can think of right now.