Multimode source (Agilent) issue

[Trishia]

We have an Agilent multimode source (APCI-ES, 6120b) on our HPLC/MS. Hadn't used the system in a while and we are currently experiencing a complete flatline when running samples in ES mode (both negative and positive), but we get a signal with APCI. We can tune in both modes and see the peaks/signals but when running a sample, it's a complete flatline with no noise whatsoever... Any idea what we should be checking?

Thanks

[Ian_R]

We had the exact same problem with ours. Tried taking the nebulizer assembly apart. The area around the charging electrode and reversing electrode was filthy.Tried cleaning it but no luck. Suspect that was the problem as these lenses are very close to each, and have a potential difference of several thousand volts between them.
Gave up with it in the end and bought an ESI only source on the basis a new source was probably not much more expensive than a service visit.
The MultiMode source is a nice idea, but in retrospect I prefer the simplicity of individual sources.