AGAweb Tech Tips
Vox Cambridge 30 V9310/9320 Tremolo
|by Robert M. Braught|
As some of you techs know by now, the tremolo 'assembly' (opto-coupler p/n LT9914) has a reputation for failure... causing distortion in clean channel operation, poor/no tremolo... one on the frizz can make the amp sound like the output IC's blown...
Word from Korg USA last week, no 'recall' in the near future, no substitute part recommended, etc. From my field experience it appears the LDR portion fails, possibly linked to voltage/current (? customers have reported after 'blasting' signal through their amp, it 'quit'.) List price on the 'original' Vox(Korg USA) part $24 :(
I've successfully tested a 'regular' Vactrol, ala Fender p/n 16282, OEM # VTL5C3/2 as a suitable replacement. Use both LDR elements in series (leave the center wire unconnected / clipped.) The circuit will require 'recalibration', twiddle ref VR11 and VR12 (on the main board) 'til tremolo sounds right ('normal' full depth) and signal pass is good with tremolo 'off'. No harm will come from the adjustments being dimed or turned back full CCW. This sub is less than half the part cost of the orig Vox part, and my experience with the Vactrol units (as in Fenders, etc) is that they are a very high reliability part, with long life expectancy. FWIW this will not change your tone. :)