Harlem Globetrotters wont go in attract

[kamalackarie]

Hi all
while working on the sound board i managed to short my multi meter on the Ground but touching it with the red probe.. some sparks followed

Now the game boots - i get 7 flashges of the MPU and at the point where it should go into attract mode nothing happens - I have Gi thats all - all fiuses work . I am assuming i have blown something on the MPU - but where to start?

 

[kamalackarie]

MPU is the Altek

 

[Paul]

not familiar with th Altek, however on the original boards if you are getting 7 flashes however then nothing...

if your getting all flashes and it sits idle your missing the 21+v input from the SDB to the mpu check TP3 for the 21v on the mpu

I would check all voltages first to make sure you are getting what you expect into the MPU..

 

[AlanJ]

Double check all fuses

Btw The 21v comes from the 43v it’s derived on the mpu board itself.

Remove the connector to the sound board, see what happens.

 

[kamalackarie]

Double check all fuses

Btw The 21v comes from the 43v it’s derived on the mpu board itself.

Remove the connector to the sound board, see what happens.

Thank you Alan - that fixed it.......would you mind letting me know what i just did to fix this?

Glad to have gotten this as the last remaining cmponent arrives today and if im lucky i may hear some soiunds..

 

[AlanJ]

What fixed it ? Removing the connector to the sound board? If so it’s usually bad caps or voltage regs in the sound board.

 

[kamalackarie]

Yes removing the sound board connector fixed it . I ahve now been going over the sound board component by component to find the culprit
Prior to all of this happening i was not getting 12v from TP3 on the sound board - was more like 6v.
Noticed that R36 was burnt out- replacement arriving today i hope...have lots of caps here so hopefully can swap out the bad one

 

[Jay Walker]

aBtw, that quote "if you get all flashes and it sits idle.. 21v from solenoid board is absent" doesn't sound right - as Alan says, the solenoid voltage 43v is fed to the Mpu board, and cut down to 21v to supply the 'Zero Crossing' circuit. And if it was absent the Mpu test would fail at the Zero Crossing stage (shown by not making the 7th flash of the l.e.d. and halting there).

 

[kamalackarie]

so i tested the caps on the soundboard and C12 is dead.I have been searching on line find a substitute Cap as the one on the board is obselete. Is there any oline reference for substitutions? or can anyone advise on what to replace it with...

 

[drhex]

.1 uF 25v ceramic cap. You can go higher on voltage, would stick to capacity.

 

[kamalackarie]

Cheers i have them on order for delivery tomorrow. Can i check that a ceramic cap will do the job - the original was not ceramic ( see pic of C12)


I just tested with a 1uf 500v ceramic i had here - did not work - hoping the 25v ones tomorrow will solve this - if not back to the drawing board

 

[kamalackarie]

Evening all. after swapping out the Cap i found a dead diode that i replaced. Then after some research on line i learnt that in my situation (pins 12 onU4 and U5 not pulsing, `thst they needed to be replaced.
swapped them out and i have sound.

Thank you all for your help