Ideas on trouble shooting mute/phase switch and input cable noise on vp25

Hey there,

I've been trying to track down the cause of pops in one of my vp25 channels, and haven't been able to figure it out. Here are the symptoms:

Unlike my other three CAPI VP25 channels, this one had audible pop when engaging/disengaging the mute and phase switches. Has since I got done with assembly. Also, there is noise that is audible whenever you tough the input cable coming into the channel. I've switched it to numerous 500 rack positions, just to make sure it is the unit (not raack connector), which it definitely has to be, after trying different spots.

I've reflowed solder joints and replaced the switches with new ones, but the problem has remained.Everything else works about the channel, Passes signal, phantom, etc. Just every time you hit one of those switches there is a pop and touching the xlr in makes crackles, but in every position in the 500 rack.

I'm not really sure where to look and it bugs me that this one channel isn't working right. Any tips or direction appreciated.

Look for a discharge resistance that may be open (poor solder connection). Without the resistor discharging voltage build up, it can pop when selected.

JR

Can you measure for DC on switch?

The noise or pop is DC or could be HF oscillation. If you are moving the cable and you get noise it could be either type of the problem. As John & Pucho  said look for open resistor , DC volts on the cable connector.
Check it against another working module
Duke.

Thanks for the responses. I have a multimeter, so I should be able to measure voltage.

Seems like I should go ahead and reflow solder on the resistors' pads, just to make sure that I didn't miss a cold solder on previous tries. I have a "test jig" and can pull the module out to check voltages, but I don't have a second one, to be able to compare "in real time" or without checking each point and then pulling a second module out to do the same.