Vox AC 30 Voltage and popping problem.

[Rockstar Okan]

Hi guys,

Are these voltages normal for VOX AC30? I rebuilt this amp with new board and parts to original ac 30 chassis.

32V DC at PI grids when working, -550mV at 2 of EL84's grids when standy by.

In addition to these, amp is popping when i hit the cabinet. And also harshness sound at high volumes (vibrating cabinet).

Could you help me please? Could you show me the way? I can post photo or video, make voltage or scope readings as you want.

Thanks. Okan

[gearhead63]

So you have -550mv only on V5 and V7? not on the V4 and V6?
What kind of voltage are you looking at on all four EL84 grids when out of standby mode?
Maybe you should look at this:
http://www.ampbooks.com/home/classic...c30-power-amp/

[g1]

Please post the complete schematic of your build, including the standby arrangement.

[Dave H]

32V DC at PI grids when working

You often get silly readings when measuring the PI grids. Try measuring the the common PI cathode connection. I measure 60V there which is similar to the voltage marked on the AC30 schematic.