Mystery Castle fuse blow

[scottnds]

Hi just wondering if any can help.I have a Mystery castle that keeps blowing the fuse to the 'eject to playfield' coil.I have tried 2 different coils and it does the same thing.I have tried continuity to earth off both terminals and both sides of fuse holder and seems OK.Any help would be much appreciated got visitors keen to play.
Thanks
Scott

[Homepin]

shorted driver transistor?? It's a mystery 

[benpin]

Have you replaced the chip (IC) that drive the transistor that fires the coil for the eject hole

[scottnds]

I have not.Would need to know what I was doing.I dont mind giving it a go though.Are there any links or tutorials on it.

[beaky]

make sure the diode is not shorted with your multi meter (you will have to remove 1 Leg of the diode from the coil to test this). also make sure you have the wires on the coil and diode the right way around.
the red and orange wire should be at the end of the diode with the line and the blue and red wire should be at the end without the line.

make sure the fuse that you install is a 250ma SLOW BLOW fuse.

if the above is all fine then check if transistor (mosfet) Q50 on the cpu / driver board is shorted.

(the schematic I have is not very clear so i hope I have all of the above right)

[scottnds]

Thanks Beaky.I suppose what Im thinking is ...should I be mucking around with circuit boards only having had pinball machines since may.Having read a few sites on boards they do warn that experience is esential and send your board to professionals.I am assuming coil diodes are ok as I have tried 3 different coils and all blow fuse.I have been using 500ma slow blow fuse as I am in Portland Vic and that is the lowest I can get around town(will get some on line)I also saw on one site that a new board is only $30 would this be a better way to go considering my inexperience at soldering and fault finding.On the plus side the cricket is on .Cheers Scott.

[Homepin]

Thanks Beaky.I suppose what Im thinking is ...should I be mucking around with circuit boards only having had pinball machines since may.Having read a few sites on boards they do warn that experience is esential and send your board to professionals.I am assuming coil diodes are ok as I have tried 3 different coils and all blow fuse.I have been using 500ma slow blow fuse as I am in Portland Vic and that is the lowest I can get around town(will get some on line)I also saw on one site that a new board is only $30 would this be a better way to go considering my inexperience at soldering and fault finding.On the plus side the cricket is on .Cheers Scott.

I think you might be mistaken thinking a new driver board is $30????

More like $300.....maybe you are looking at the wrong board or we are thinking different things??

[scottnds]

They are at PSPA for 30 bucks but out of stock.

[Homepin]

They are at PSPA for 30 bucks but out of stock.

I have 1oz gold ingots for only $10 including express post but alas I am out of stock!

[scottnds]

Ha .Good to know.
Do I have to remove transister from board before testing.If so I probably should just replace it anyway.
Thanks
Scott.

[beaky]

you can test it on the board.

[scottnds]

Sent board to Beaky.Replaeced mosfet, driver ic and cap for mosfet and much advise along the way.Just put board back in and fired up straight away.Thanks for all the help Beaky I think I actually learned a little .Legend.And good advise from Nick not  to stuff around with boards myself.Cheers.

[pinnies4me]

Great to hear it's up and running .

[beaky]

your welcome.

The strange thing was when I bench tested the board I could not find a fault.
I replaced the mosfet with one that has a higher amp rating, the i.c. that controls it and the cap that is across it in case one of them was failing under load.

the desc ription of the fault was the coil would fire when it was supposed to but it would then blow the fuse yet the coil and diode were testing fine

I also supplied a couple of good quality 250ma slow blow fuses in case it was a batch of bad fuses. (but I wonder what blew the original fuse? I assume the coil was firing then locking on)

I am glad you have learned how to check for some faults your self also