424 MK1 transport keys do nothing

[Joshua]

So I bought a used 424 MK1, everything powers on quite nicely and lights up, except for all the transport keys (Play, Pause...) . They don't light up and don't do anything. I'd like to do more testing and get the thing to work fully, do you have any ideas how to fix this?

Josh

 

[Borchmore]

Have you checked the connections on the transport keys? I believe they should be on the SW PCB, which attaches to the bottom PCB with a cable connector. That would be my first guess after making sure the cassette works and cleaning the buttons

 

[Joshua]

I have checked all the switches from the SW PCB, and they work fine. Also the ribbon cable to the BOTTOM PCB looks normal. I have noticed however, that my 424 looks different to others. It has an additional PCB which says "POETTER", that is connected to the SW PCB via 4 wires. Plus it has a SYCHRO Connector on the side of the chassis, which is connected to the POETTER PCB. Also it has an additional LED on the front which says "NORMAL". I'm thinking that maybe I need to connect something to the SYNCHRO connector to get the transport keys to work? Anybody familiar with this 424 variation?

 

[Borchmore]

Yeah, that looks like some sort of mod someone threw in there. I'm guessing it was used to sync multiple Portastudios; maybe the transport keys are disabled so that multiple Portastudios could be controlled with one set of keys? I would just remove that POETTER board, though that might mess something else up so IDK

 

[Joshua]

I did some research and it looks like this modded machine was invented to allow synchronization with film to record film sound. It's only in german, so I translated it:

As an alternative, Pötter has developed a cassette recorder called PÖTTER MIX 4 (10), which is based on the 4-channel recorder from TASCAM. Here, too, a synchronous controller, a perfoleselector and a pulse-reading head are effective, so that the mode of operation is similar to the above-mentioned UHER device. The presence -besides the synchronous track- of three other tracks and a mixer, allows with this device the multi-channel elaboration of complete dubbings. Special Perforex cassettes -which have a round hole on track 3- as well as impulse cassettes, which can be produced from normal sound cassettes, ensure cost-effective synchronous operation.
The normal functions of the first-class small studio are unrestrictedly preserved.​

(http://www.meinepatenkinder.de/poetter-Dateien/poetter.html)

It says the tascam should work normally also, but this is not the case. I think I'll try removing the mod to see if it works then.

 

[Borchmore]

Oh, that site is actually pretty interesting. Looks like they made film synchronization products back in the day? I could actually understand most of it lol, one of the rare times my German studies have helped me :^)

On second thought, I'd honestly keep that in just for novelty. Maybe just try disconnecting the wires connected to the SW board for now. Also bear in mind, I'm kinda new here and am not really an expert in electronics repair. Just throwing ideas out there

 

[Joshua]

So I removed the wires from the SW PCB, but still the same.

 

[Borchmore]

Whoops, sorry I made you do that then lol. I guess signal testing would be the next step, but I'm not sure where to start. Maybe start by making sure the SW PCB is properly grounded and the ribbon cable sockets are soldered okay. If the board itself didn't go bad, there's probably a bad connection somewhere making the whole thing malfunction. Or something like that