424 mk iii with bad XLR input

[ciemnika]

Hello, I just bought a mk iii 424 to replace my mk ii, and the guy I bought it from thought it was fully working (he’s the original owner but hasn’t used it for a long time), but it turns out XLR input 3 isn’t working. Line in 3 is fine and the trim knob is fully functional on line in 3. This leads me to assume that the actual XLR socket is dead. I hit it with some DeoxIt to see if that would resuscitate it, but it didn’t help.

The XLR inputs aren’t of much importance to me but I would like the machine to function fully. I’m totally comfortable replacing the Neutrik connector myself, but I don’t want to go to the effort if that’s unlikely to be the culprit. I’m not familiar with the guts of these things, so I don’t want to get in and just start doing exploratory surgery.

Is there anything I’ve overlooked? What would someone who knows more than I do suggest here?

 

[ciemnika]

Closing the loop with an update. I opened up the 424 and it could use some love. I’m taking it to a well regarded company near me called Music Technology, in Springfield, VA in a few months (their backlog for work is currently +/- 4 months, which I’m taking as a good omen like a busy restaurant) for a full restoration to “good as new” status. It’ll be a little costly but I’d like to hang onto the unit forever, so I think it’s worth it. Hoping to have it repaired by end of year.

 

[SkywaveTDR]

For such a low end product I would not take it there. They are known for charging a fortune and then breaking other stuff on a unit- I have talked to their customers. I am working on a Mk III unit now and XLR connectors never fail- it is either solder joints or bad circuits. Being the one I have here was made in China I can say that the build quality is even worse than those cheap products made in Japan. To think you are moving up from an older unit to a newer one is always a mistake and I have seen it many times. For instance a 122 Mk II is a better unit than a Mk III and the Mk III has half or less the pots for adjustments in them so what they do have is a compromise. A single bias pot for Chrome and Metal tapes is NOT an improvement. I am a past Lead Tech from a Factory service facility so I have worked on these kinds of things a long time and it may be near 47 years now. I am still working on them now.

 

[SkywaveTDR]

XLR wise I would look for broken- cracked solder joints on the PCB's as the build quality in these boards and really even less than consumer grade. In other equipment I often resolder a lot of joint to insure reliability- my solder joints with Kester 44 are as good as you can get. I had further training at Hughes as well as a NASA solder training course. The only reason to use XLR inputs are for Mics. If you are not worried about that then I would leave that alone and not spend a fortune getting something fixed that even a high school kid could do with a good soldering Iron. In my work of 14 years in Radio we never had any XLR connector fail- it was always a broken off wire or some other reason. They are kind of too robust to break. Solder joints that connect them is another matter. Have a look at that board first.

 

[SkywaveTDR]

Strange that one came in that I had to fix. Gads what a transport from China. I will have to look at the XLR input. The3 XLT inputs are very easy to get at. There is a board they are soldered into and that is where the cracked joint will be. The fact that Cannon, Switchcraft or Neutrik connectors are long they allow for the torque to upset the solder joints- the plastic they are mounted in offers no support at all. You might have to disconnect a bunch of connector to the top section to be able to turn it around to work on it. Heck I had a broken solder joint on the line out RCA and I fixed that plus did a lot of other resoldering of bad joints. Now I just have to calibrate this. It might be ready to go out tomorrow. I already fixed an X10 that came in today- trying to get stuff out of here.