Hook - ouhole coil firing continually

[robm]

I am helping out a guy with a Hook that was had no high power for the solenoids - turned out the problem was the outhole coil (ie: the one that kicks from the centre drain to the end of the trough) was melted. The tip122, and 2N4401 (Q46) and matching resistor were all blown to pieces - in fact theres a decent scorch mark that may have caused further complications. I replaced these and the f5 fuse has stopped blowing, but now the 8A fuse in the backbox for the Bridge Rectifier for the 30V AC circuit blows continually.

To try to further isolate the problem, i put a Rocky and Bullwinkle CPU board in hook (put in the Hook PROM and RAM)

1. Can i do this, do i need to change anything else, or may this lead to other problems?

After i did this, the game seemed to run OK, but then it was firing extra balls out and trying to reset the drop targets continually at one stage. I noticed that whenever a switch that drives a solenoid is hit (ie: drop target, slings etc) that the outhole coil also fires at the same time - EVERY time. I'm starting to think that if this was happening before, it may have fired many more times than it is designed and may have heated up and melted....

2. Is this logical or way off track? And where can i start looking to rectify the problem

The last thing i did was test all the coils - all resistances are around 4 - 4.5, although the diverter coil is about 15....but as this is only turning a small diverter does it have greater resistance so it doesn't slam into the side of the ramp???

I've now brought the CPU, PPB and power supply boards home for further testing.

3. I replaced the 7408 IC as well in case it got fried, but am wondering if the PIA got damaged - can i test this, or is it very unlikely?

4. Any other help....

[dj10555]

Hi Rob,
On Data East games if the outhole coil is firing when a switch is triggering, this is normally caused by a fault on the PPB board. This board shares transistors between flashers and coils and the relay selects between the two. If the relay is not working then coils will firing instead of flashers being triggered. The relay can go faulty but the most common cause is dry joints on the relay or dry joints on the headers pins which lead to the relay. The Tip36C also tend to fail if there was a faulty coil in the game.  Also worth checking the GI connectors on the PPB and PSU while you have them out.

Also quite common for the 6821 to fail in this game. The easiest way to test these are to burn a copy of Leon's DE Test Rom from www.pinrepair.com With this Rom installed it will toggle all the inputs/outputs of the 6 PIAs so you can test these with a logic probe. Make sure the board does is not connected in the game while running the Test Rom.

regards Derek

[robm]

YYIPPPPEEEE finally sorted this out.

Worked on it from 8:30 till 3:30  - ended up being the relay on the PPB board was stuck on one side - from what i understand this meant it wasn't switching from left to right but rather switching left AND right at the same time (ie: firing two switches - the outhole coil every time another switch on the bottom half of the playfield was triggered in this case).  Ended up scabbing a relay off another game and it worked fine

For interests sake and reference i found a few other interesting things....one of the small relay assemblies was testing strange on one of the legs - it turned out that once i replaced the IC  that was further 'downstream', the resistor assembly all tested OK - i assume this was because there was an internal short in the IC causing the strange readings.

Anyway, learned a heap more about these beasts today and was a great feeling once i got it sorted.