M4 Input jack Problem. Advice ?

[Paul Secondino]

My front input on my M4 preamp is sketchy and since it is PCB mounted, I thought I would ask for any advice on how to deal with possible solder repair if necessary before I actually take it out of the chassis. Thanks

 

[bruce egnater]

Hey Paul. What is the jack doing? Probably just needs to be cleaned with the "right" spray contact cleaner. The very best contact cleaner for audio stuff is made by Caig Labs/Cramolin. It is available at GC. Get the one with the red label. Use it sparingly. Only takes a little bit to clean. Just spray a little bit directly into the jack from the outside and insert a plug in/out a bunch of times. Repeat is necessary. FYI, we have never had a solder connection break on a jack on any modular stuff.

 

[Paul Secondino]

Hi Bruce.
It was fine for about 1 month or so when I bought it and then one night it started sounding the way an amp sounds when the input jack gets weird. If you wiggle the jacks a little back and forth, the signal clears up. So at the moment , the signal can get sketchy when I play or cut out entirely .

I did try cleaning it with Deoxit first but physical manipulation is the only thing that seems to affect the signal. Also, if I plug into the rear input, which seems to be fine, I get similar noise and cut outs as the two inputs seem to share the same path.

 

[jlbaxe]

DId ya try a different cord?

 

[Deleted member 3860]

...

 

[jlbaxe]

Check for a dying main input tube.

And a loose mod or dirty contact. My mod50 would would sound like the reverb tank was being hit when I touched the top of the amp. I had it un plugged and changed all the tubes and I could tap my fingers on it and it would come through. It also would create a strange buzz feedback on certain notes being played at low or high vol. Was slot 2 mod loose even with the thumb screws in.

 

[Paul Secondino]

Tubes , cords and modules are fine.It's the input jack. I'm going to take it out and check all the solder points. If the solder hasn't failed then it's the jack itself and I'll have to replace it.

 

[jkdsteve]

For what it's worth, there a small signal cable goes from the front board to the backplane; it has white, PCB style connectors and carries the input signal.

This cable failed on mine (bad or broken connection near the header) with similar symptoms...although physical manipulation was obviously not a guaranteed fix for mine...it would work only 'sometimes.'

 

[Paul Secondino]

I'm looking that over right now and wondering if it is my issue. Thanks for the heads up though

 

[jkdsteve]

I'm looking that over right now and wondering if it is my issue. Thanks for the heads up though

Only thing I can't recall is if the back panel input jack routes it's signal through there also...

If it is this at fault...lemme know if you manage to get Egnater to send you a replacement..I think my PM got lossed in the masses

I pulled mine and replaced the length of wire with some dual core small headphone cable I had around..never been a problem since.

 

[Paul Secondino]

Solution

As soon as I loosened the nut that holds the input jack to the chassis , I noticed that the screw on the PCB that holds the jack to it was loose . Easy fix, just tighten it up with a screw driver. If any of you have issues with your input jack, check that screw on the PCB. If it gets loose, the jack can move a bit and loose good contact with your cable.