Soundcraft Ghost problem. Some channels with 0dB signal without input signal

[LightningP]

Hello all,

I have an Soundcraft Ghost 32 LE console with meterbridge and some problem with 2 channels.

While switching on the powersupply, as a test/check the console shortly puts all VU meters at the bridge on and then fast the VU meters at the bridge go off. Up to this point everything ok.

When the powersuply is switched off and a few minutes later on again, in about 50% of the cases 2 channels go to 0 dB level and remain at this level. Sometimes they fall back slowly to no signal. Everything without anything connected to the console.

Switching Channel/Mic, Rev and Phase does not influence it. The low cut filter (LCF) switch however does solve the problem. Switching LCF on off brings the particular channel to peak level and slowly in falls back to zero signal. plugging a jack plug in and out into the insert plug solves it as well. The time the console is switched on the problem does not araise again.

Note: I know it is known the insert chasis parts can be dirty and give intermittant signals at this console. However I cleaned them all with alcohol and resistance off all jack chasis parts is 0 Ohm. I am quite sure I excluded dirty inserts as the cause of the problem.

I tried to exchange the big channel circuitboard with another channel leaving the fader and I/O connection print at its place and then the problem moves to the new position. So I conclude the problem is inside the big channel circuit. Can it be a bad/dirty pot meter? The gain knob does not influence the problem at all. As well not at full gain. Can not find bad/broken solder points as far as seen/measured now.

A last observation. The 0dB signal that is present is only noise and can be routed to a subgroup e.g. When solving the problem by switching de LCF on and off the signal at the subgroupbus is gone immediately. While it at the channel meter is decreasing very slowly. Say about 5 seconds.

Somebody an idea to solve it? Is this a known problem? Maybe a problem in the LCF? I'm not the first owner so don't know if some input signal destroyed the input part of the print.

Long story but already thanks for a response.

Pascal