Tascam 424 buttons unresponsive

  • Thread starter Thread starter notbillcosby
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notbillcosby

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I just got a very very cheap 424! It didn’t power up at first, but after fixing the broken connections at the power jack it is doing fine. The capstan is spinning, but none of the transport buttons seem to do anything at all. It doesn’t even try, it’s like the board with the buttons is disconnected. But it’s not! I’ve opened it up and re-seated the ribbon cables that connect that board but nothing changed. Is ther a chip or cap(s) that tend to go out on these?
 
There's not much helpful info out there on this. It's definitely a common problem with these units.

There's a bit of info H E R E - scroll down to the post by TMOQuantity.
 
That post talks about the motor wearing out, but my motor is fine. My transport buttons do nothing... the heads don’t try to engage, the reels don’t twitch, nothing. Did I miss something on that page?
 
Probably not. The motor is one possibility. Some talk of drive belts, but everyone says theirs are fine - so a no-go there too. There aren't a lot of solutions other than to repair with very hard to find parts, or replace with a newer model.
 
I can’t imagine it’s an issue with the board that has the buttons on it- there’s nothing on that board but buttons and maybe LEDs, I don’t remember offhand. It’s gotta be either an issue with the ribbon cable or some component between there and the transport. Maybe a blown cap that my eyes didn’t spot? Maybe an IC that has gone out? I’ll do some further investigating. I guess the next step is to check continuity on all pins of the ribbon. I’ll report back.
 
Just wanted to ask if this problem was ever solved or if anyone else on here has any clues. I’ve got one with the same exact issue right now! Can’t figure it out.
 
I hope it can help somebody, I just got a unit with the very same problem. Turns out it was missing a cassette switch. There are two switches, one in the back that is activated once you first put cassette and the other one is on the bottom and it is activated when you push the cassette down in place. For me its the later that was missing, the little pin who push on the leaf switch on the bottom was missing. If one of those switches is not activated, a condition is not met so the logic in the uPD7566 (U502) is disable and therefore it doesn't send the appropriate voltage to the LC7800 (U501) chip pins SA SB SC SD. If those pins don't drop to 0V, then the associated input pins of the LC7800 (A0, A1 ...B0, B1...etc where the buttons are connected) cannot trigger the outputs O0, O1, O2, O3 of this chip.

This part is hard to find so I am printing it in 3D, the unit should be up and running in no time.
 
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