Topic: Fostex VF160 EX input jack weirdness

[cyfan]

This situation has me really puzzled so I thought I'd post it here and see if anybody has a clue as to what might be happening.

I have this Fostex VF160 EX unit I use for 8-channel recordings. It has 1/4 input jacks and I've generally used it with no trouble for several years.
When I have open channels to put mic feeds into the mix, I run the mics through a UA-5 preamp and go from  the RCA jacks on the back into two 1/4" inch inputs on the VF160. (the pres on the VF160 EX suck on their own). So this has never been an issue for years and saves a lot of time vs. synching mics up in post.

But a few months ago, when I was using this set up (tapouts in channels 1/2, some guitar directs in chanels 3-6, and the mics in channels 7/8) I noticed I was getting no signal from one of the mics (channel 7). After pissing around with it for awhile, pulled the 1/4" plug from channel 6 and moved the seemingly dead mic source into its place and it worked fine.

My assumption was that the channel 7 jack was crappy. Without having time to mess with it before my next time out, I set up to pull 8 channels of soundboard direct outs and discovered channel 7 was working just fine again. Hmm.

Move ahead a week and I"m preparing to record a solo acoustic act and set up with the soundboard tapeouts in channels 1/2 and the mics again thorugh the UA-5 into channels 6 and 8. I avoided channel 7 due to my problem before. This time, channel 6 did not have any signal. Shit. I pulled the jack from 6 and put it into channel 7 and it worked just fine.

This has been going on for some time and I"m really confused. Once this happens, where the mic channel appears not to work, I can't get anything to work in that jack for the rest of the evening, even by turning the machine on and off a few times. But it works just fine the next time out (provided I haven't run a mic signal into it).

None of my more tech'y friends can figure this out. It's like the initial signal from the UA-5 left mic zaps the channel for the rest of tthe night. I've tried different sequencing (turning on UA5 before putting int he 1/4 inch plugs, putting in 1/4" lugs before turning on UA5) with the same problem.

[yousef]

I've only had my VF160 for a couple of weeks but I think I've noticed something similar - on a couple of occassions a particular channel behaves as if there is no signal present. It seems to resolve after I whack the gain up to full a couple of times.

Looking through the VF16.com archives it seems that a few people have had similar problems from time to time and a similar "flushing the channel" approach seems to have worked for them. Which obviously isn't any sort of explanation of the underlying problem or an indication of if it is, as I fear, a warning of imminent channel death.