9 times out of 10 if resoldering the ringed solder connections doesn't
give you a full picture then the vertical output chip is bad. With
Zeniths usually all you need to do is replace the VOUT chip (it doesn't
cost much) and that will do the trick. To the naked eye the vertical IC
may appear to be good but could be bad internally. It could also be a
case of the VOUT not getting the proper Vcc but you'd need a schematic
to look up the voltages. WHat is the number on the VOUT chip?
Mark

"The Vertical IC appears to be good. I touched up the solder joints just
to be sure also checked values of nearby components but everything
appears to check out. I think I'm missing something.
- Vince"