Taito cocktail cab no Sound

[Retroman839]

Picked up a taito cocktail cab yesterday.
Guy told me that it has had no sound for many years now ..

So …
I just thought I would pull the pcb and check it in my test rig .

Finalizer sound works

Pcb is all working ..
So what’s wrong with sound on my cab then ?

Hmmmm I’m suspecting maybe a bad 12v+ from psu ..

Time to check the 12v+ on psu…

Cab is wired electrocoin standerd .
So time to make a electrocoin to jamma converter also ..

Finished loom
Only 1p for now just to test

Utilised some bits I had

 

[Lurch666]

Or connection between PCB and speaker.
Or bad speaker.

 

[Retroman839]

Or connection between PCB and speaker.
Or bad speaker.

next stop take multi meter to the cab check out the 12v
And continuity to speaker ..

I can’t find the 5v adjust pot yet ..

I have found the -5 and -12 pots ..
I’m hoping +5 isn’t under the cage ..

Unless in reading where it says -5 wrong and they is the 5v

 

[Retroman839]

Yeh so my 5v is

5.46v

My 12v

4.05v

And my -5v

2.44v I’m guessing that’s -2.44v?
As my meter is on 20v dc

 

[Retroman839]

Super cobra in now runs fine no sound


Tried pots all way clock wise and anti clock wise I’m not even getting 1 volt swing either way ?
Bad caps ?

My loom is ok unpopulated


I don’t know where to find the 5v+ to dial it down a bit though ?

 

[Retroman839]

12v+ under load is 1.2v

 

[Retroman839]

Tried power spikes ..
My adaptor is old and power spikes board is really thin ..
So contacts are not making great contact but all controls work..
And got a full colour picture with a little persuasion .
So far so good ..

I guess the psu is I need of som tlc

 

[Retroman839]

+5 cunningly hiding underneath the output connector B making it impossible to see and adjust with it in cabinet. ( oversite on design ,perhaps
Psu was designed to lay flat but due to cabinets small size they stood it up?). I may try to do something here as I most likely will need to be able to adjust my 5v+ to suit different pcb and it is not convenient .

5.4v+ now dialed down to 4.8v+ for now

And super cobra running happily

So .. 5v+ rail is fine …

Issue is on the 12v+ & -5v only