Gottlieb system 3 Flash lamp always on

[Martin.D]

Posted similar problem on my World Poker Tour (Still tracing that fault), so thanks to lukewells I have better understanding of where to look.

Cue Ball Wizard Red Flash Lamp (18) on Relay & Solenoid test remains on all the time, but also behaves odd when tested lights a little brighter and when machine turned off does not go out quickly (Specially if I install LED flash lamp).
So I check Q19 listed on schematics and test transistor, resistors & capacitors in this area. The all operating that same as one another apart from capacitor C30 who reads 1400 not 1900 in direction and 1000 not 1900 when swap the probes.

Is this the source of problem or should I be looking else where?

 

[drhex]

How do you test the cap?
Usually the driver shorted out. The coil power caps are discharging through the lamp when switched off which is why it stays lit.

 

[Martin.D]

How do you test the cap?
Usually the driver shorted out. The coil power caps are discharging through the lamp when switched off which is why it stays lit.

You are right. Was not testing transistor mosfet correctly. Thanks to YouTube video for that one. Sadly not much experience fixing or finding these types of faults. Still learning
Transistor mosfet Q19 appears to be faulty, test passing current between drain & source. BUT another test I learned can lead incorrect testing as possible activate without knowing.
Hoping capacitor C30 is not damaged. Planning to replace transistor mosfet and see if this fixes fault. Will put post results here.

BTW any idea where to get Capacitor 0.1uf 10_ 50v as listed in Gottlieb schematics? Can not seem to find anyone selling them.

 

[drhex]

All the big parts suppliers should carry them, eg https://uk.rs-online.com/web/c/?searchTerm=0.1+uf+100v

 

[Paul]

BTW any idea where to get Capacitor 0.1uf 10_ 50v as listed in Gottlieb schematics? Can not seem to find anyone selling them.

I'm pretty good at locating components. Got a pic of it anywhere?
Is there anything else listed in the parts list/cct diagram that gives any more info about the type (Tant, Elect etc)
0.1uf @ 50v sounds like a decoupling cap...

 

[Martin.D]

Just rechecked schematics lists Capacitor 0.1uf +80% -20% 50v, part number XO-229 Reference U1.
Few places in US but not in UK.

 

[Paul]

Drop me a PM Martin - i have hundreds of those - will throw a few in the post for you...

 

[Martin.D]

YES problem sorted. Removed old component tested new transistor mosfet attached using probes. Red flasher now working, not sure long term how capacitor not 100% will effect new part.
This brings me on to finding someone local to help with replacing components on PCB.
Have solder iron and ok with the basics. Removing & replacing components on pinball circuit board maybe little beyond my skill. Specially the down side of getting it wrong.

 

[drhex]

Good thing, why di you think the cap is gone? You can always send boards to me if you cant find help,more local.

 

[Martin.D]

Good thing, why di you think the cap is gone? You can always send boards to me if you cant find help,more local.

First test showed capacitor C30 not at correct capacity/level compared to others in same row. Will test again once install new transistor mosfet or just replace it anyway at same time.
Thanks for offer to look at board. Will drop you are line if can not sort locally.

 

[drhex]

How do you test the cap in circuit?

 

[Martin.D]

Resistance mode (have no capacitance setting) range 3000. First discharge capacitor, than connect probes get reading of 2556 (+/-). This same result on capacitors on both side of the one I am testing.
Think results list at start of topic not tested correctly. Likely not discharged and transistor mosfet broken.

 

[drhex]

You’re then measuring charging current essentially. This is mostly meaningless. You’d find a shorted one of course.

 

[Martin.D]

You’re then measuring charging current essentially. This is mostly meaningless. You’d find a shorted one of course.

Yep find one not work was goal, but harder to tell if damaged using this test?

 

[drhex]

Unlikely it is damaged. To figure that out you have to unsolder one leg and measure it separately with an LCR meter as the FET has a parallel capacity. Easier to change it out. This is there to limit the switching speed of the FET which shouldnt be an issue with a bulb anyway.