@Gaspardeden
Ah. This explains a lot. I appreciate the additional background info and I’m sorry if I was quick to judge. Like you I too did some ugly looking work…and it still happens sometimes…sometimes it’s unavoidable…and it took me a long time to understand better technique and good equipment…trial and error. And yes the ugly work accelerated my skill-building with repairing my own damage lol!
I wish I had a desoldering gun…not in the budget. I do have a nice spring-loaded vacuum sucker, and honestly the thousands of solder joints I’ve desoldered with that type of tool I don’t know if I could get used to a desoldering gun, but I think it would be helpful when working on double-sided glass fiber PCBs…and that’s the only thing that’s in my Studer console. I kind of dread the day I really have to recap it.
Okay, fair enough. If you do get a chance to retrace your steps on that do post what you determine here. We can at least do a little forensics to establish the scope of what might have happened when that was done. Maybe it was inconsequential to any of your ongoing issues and you can put that behind you.
Your transport issue I’m sure is really annoying. I’m sure you want to have reliable operation. You’ve worked really hard to get there, and my goal isn’t to discourage you, but to offer an opinion that maybe will help save you from long term aggravation. Servo transport issues are difficult to resolve when they are intermittent like that. And what you have to do is start working through how the servo system works and checking that each part of the system is doing what it’s supposed to do. The problem is by the time of the 388 Teac stopped including any operational theory in their service manuals. You look at a manual for a 244, 234, 58…dozens of pages of detailed walk through of how the thing actually works…how the circuitry does what it does and it references each component…”leg bone connected to the hip bone” style. You can go to the Theory of Operation section with schematics in-hand and literally walk through what’s happening in the circuits and how it works. And there is detail of “you should see this happen or measure X-Y-Z when you press such and such a button” or “when the transport is in mode X you should see a square wave of X frequency on your scope when you measure between test points X” and you can actually understand why you should see that square wave. And then when you don’t see that you already have an idea of what might be in a failure state and you can check it out. It’s extremely valuable. It’s like the ultimate troubleshooting section. The 388 manual has none of this. It’s one reason I prefer the original first generation 122 cassette deck over the mkII or mkIII generations…original 122 service manual? 122 pages…mkII service manual? 52 pages. What’s missing? Allll the “here’s HOW it works and WHY it works” stuff. And for me, an unschooled untrained hobbyist electronics technician, I don’t have a hope or a prayer to fix stuff like what you’re struggling with on my own stuff if I don’t have that information…and even if I do it’s often times too much. So trying to do that over messaging when I don’t have the machine in front of me? That’s really hard. This is why I like mixers more than tape machines, lol! No motors or servos. And also why I like my old relay logic discrete component machines with no servos like my Ampex MM-1000 or 3M M64. They’re just easier to understand.
I will say though often times intermittent problems or problems that crop up with increasing frequency the longer a machine is being used or is powered have to do with heat and poor continuity. Poor continuity in a relatively high current circuit like with motors and servo systems can create a lot of heat through high impedance problem areas…cracked traces, solder joints that got super-heated during an event and need reinforced and reflowed…you said you got a replacement reel servo board…so maybe that’s not it…but you talked about smoke and such…have you inspected the joint PCBs? And sure it could be a control PCB issue too. So maybe it’s worth looking closely at those, under good light and magnification. Also running the transport with the machine tipped on its side and the bottom cover removed, gently probing or manipulating PCB assemblies and connections to see if you can either make the problem happen or make it stop. There’s also freeze spray to super chill a component. If you study the circuit and there are components that seem like they are getting hot you can chill them in operation and see if that temporarily resolves the issue, and that tells you maybe the component is at the end of its service life and/or you need to improve the continuity of the component to the board or neighboring components. So there’s a couple ideas.
