OK Baby: DDS-Credit PCB Mystery...

[Amesho]

After a few years the credit PCB in my OK Baby cab stopped working. The red LED wouldn't come on any longer, and it did not accept any coins at all. So i swapped the voltage regulator, the 100uf cap, and the 2.4v accu. With limited success. Now the cab accepts 1DM coins again, but refuses 2DM, and 5DM coins. LED stays dark now. When i try to re-program the attached RM4G00 coin accept unit, the 2DM and 5DM coins just fall through the unit, with no programming for the channels 2 & 3 possible.

Questions: What does the red square button and the blue dial on the DDS-Credit v1.3c PCB do exactly? Does anyone have more infos or a PDF on this DDS-Credit pcb?
What is channel 4: E1/1 for? Does anyone know how to fix this? Thanks in advance.

 

[stj]

obvious problem, corrosion
replace the rom,ram and cpu sockets,
clean the pins on those chips, and dump the rom.
i want to see it.
i'v never seen a credit board like that - is it doing VDAI book-keeping for use with a serial printer??

i think there is another chip hiding under a socket btw, something like a 74hc273
the c31 cpu cant directly read the memory without an 8bit latch for the lower address byte

 

[Amesho]

Seems you are onto something. When i push the bottom LGS chip down, the red LED comes back to life. Gonna take the whole thing apart later and report back. Thanks so far!

 

[Amesho]

So i took it all apart. And yes four chips are hiding underneath the sockets. Very nice prediction there. And yes there was some light corrosion, which i scraped off. I also did reflow all the socket solder points.

NOW... the red LED comes on permanently. The cab takes 1DM coins every single time, same as before. But refuses 2DM and 5DM coins, same as before. The RM4 coin dispenser unit seems to working, mechanically. But i cannot program it. Shall mean the double click indicating that the program has been accepted never happens for any of its 6 channels.

Next step gonna buy a new 10 pin ribbon cable, the one that connects the DDS-Credit PCB with the RM4 unit to see if that makes any difference here.

Alas i cannot dump the contents of the DDS rom. I don't have the gear for that. Also i cannot find any online info on this PCB at all. Its like it never existed. So no idea what the serial port does. Maybe its for rom flashing via PC or something.

 

[stj]

if you have the pinout of the mech you can just jump the pins on the credit board to test the inputs.
i'v never seen an RM4, i only have an RM5 here.
maybe the pinout is the same?
that must be a very old mech!

 

[Amesho]

I think my RM4 is from 97 or so. Its definitely pre €/Euro. Pinout seems to be the same. Gonna try a few more things and report back in a bit!