Tascam 424 Mk. 1 Buttons Stopped Responding

[Ziggy]

So… bit of a doozy. Got a 424 mk1 in good condition. A bit dusty, but everything seemed functional. After some time fiddling with my new toy, the motor seemed to start slipping. It was able to transport (play, rewind, FF) momentarily, and then suddenly it wasn’t. If I turned it on and off it would sometimes work, sometimes not. My first thought was to check the belts, so I opened her up and the capstan belt indeed was very stretchy and worn. The issue though, as stated above, lies in that when it was all put back together the buttons don’t respond at all. Everything lights up except the buttons. Is it possible I was too rough with the connectors? Or is it possibly a matter of some shoddy soldering that gave out after being exposed to fresh air? Any and all input would be very appreciated as it has been a bummer only getting to use it for a couple of minutes before it fizzed out on me.
-Z

 

[-mjk-]

@Ziggy there are a couple of things to consider. Perfectly formed solder joints will go bad over time due to the intermetallic bond growing inside. They can be susceptible to cracking if the PCB is stressed. The air has nothing to do with it and the joints don't have to be "shoddy" to begin with. Many techs working on vintage gear will often touch up solder joints to refresh the intermetallic bond.

In situations you describe, the issue is almost always with the interfacing. Connectors on cables, sockets where PCBs are plugged in, etc.. When you took the unit apart you had to disconnect modules. That is most likely where the issue lies. Something is either not put back together with the connectors fully seated, or those inter-connections may have been stressed and have broken. You'll have to go through it connector-by-connector.

 

[Ziggy]

Well that’s all good info but if you solder like a goon then presumably the connection will go bad quicker than it should… I was just throwing that out there in case it’s a common issue, I’m new to these devices. My tascam is from an estate sale, and I don’t think it’s been touched up by anybody since it was manufactured. I replaced both belts today, making extra effort to carefully review each clip’s connections to make sure nothing was bent or that none of the wires were damaged/disconnected since it stopped working after I initially did some troubleshooting. There’s no visible issues as far as I can see, and all the modules seem steady enough, which is why I was hoping there’s a common problem with the soldering being notoriously shoddy or something. Are you at least able to tell me which components the transport buttons are connected to or point me towards a manual of some sort? I’m aware of how electronics function, it’s the proprietary nature of the device I need info on. Especially since there’s seemingly no other threads with this issue.