Cocktail qbert machine

[Rush7200]

I have a qbert cocktail table and when i turn it on it blows the F11 fuse.   Everytime i replace it. I get 1 to 2 minutes outof it and then it blows again..... Anyone out that my know this problem.  Thanks

[matsadona]

In general troubleshooting, assuming there are several fuses, you need to find out what circuit that is on this specific fuse.

According to the schematics (http://pdf.textfiles.com/manuals/ARCADE/K-R/Q-Bert%20%2811x17%29%20%5BSchematics%5D%20%5BEnglish%5D.pdf) it seems to be 5Volt section of the power board.

If the 5V fuse blows, I guess there could be two reasons. Either you have the wrong value of the fuse. It should be a 6,25A slow blow fuse.
When a fuse blows after a while, it usually is because of a higher current than the fuse. If it is a shortcut it blows right away.
It can also be something wrong with your main board of course…

Have you measured that it is the correct voltage (5V)? I assume that you can change the voltage with VR1.

[boardjunkie]

A board causing the fuse to blow is unlikely. Its prob'ly regulator/cap/diode failure on the PS board.

I would keep the board disconnected to avoid damage while chasing this problem down.

http://arcarc.xmission.com/PDF_Arcade_Manuals_and_Schematics/Q-Bert_Addendum_Fuse_Correction_(2-18-83).pdf

The schematic shows F11 is right after the bridge rectifier/main filter cap and before the reg circuit.  Going by that I'd was the bridge/cap is fine and you need to look into what's goin' on in the regulator section.

[ed12]

hi
ya thats a boot-strap style reg circuit
u can tell by the :crow-bar-scr: on the final
scr11.
the pass transistor q11 >2n5679< chk for leaking,
also chk to make sure it has proper isolation from the heatsink
u can adjust the supply up/down via vr1
the best way to test this supply
is to unplug p4 and p3 and wait to see if it blows a fuse
if it dose not then take a #44 bulb and wire it to p4 :main 5volt to board:
jumper's here will do fine,again let it run,if it blow's the fuse have a good hard look at the :scr:,and easier way is just to replace the linear power supply with a switcher smp's,given the fact your ram are not bad

ed

[boardjunkie]

If he did that he's have to keep the original in place to run the audio amp and the knocker coil. So you'd use the switcher *only* for the 5v supply.

[ed12]

hi
correct
ya +5/+12 can come from a switcher
the -12 and +30 can come from the linear supply
this given the fact that his ram's are ok

ed