Getting multiple pops when turning on this amp in vibrato or chorus mode.  Multiple pops signal first detected at last IC stage of vibrato prior to going to power amp stage.  Has anyone seen this?  Is this just a normal occurrence for this amp when powering up in this mode?  When in the normal mode, I only hear the normal turn-on pop.  Of course, the vibrato circuit is not connected to the power amp in this case.

I really need a JC-120 service manual.  I have searched online and all the standard sources have removed this document.  I an looking for some one that has this PDF file.  My Amp S/N:477562