Need some technical advice

[necroscope]

Got the day off due to the rain so i have been busy trying to sort out a display problem,the machine is a sega showcase model with a whitestar board system circa 1997,the problem is when i turn it on the dmd works fine for a while and then goes blank after anywhere between 3mins and 10mins of being turned on,after reseating all the plugs and connections on the dmd ect it was still doing it anyway eventually i worked out the problem is coming from the little board in the top left corner of the backbox and if i wiggle the connector marked ch2 i can get the display to flicker back on,there is also a loud hum coming from this board and some blackened brown things,i have read on a pin repair site that the problem maybe the molex connector,would this be correct and is the hum from the board and the blackened resistor/diode thingys normal? any help and advice will be greatly appreciated.

[MartyJ]

Its a bit hard to see from the photos, but the black stuff is normal for any pinball.

Just take care if poking around the display whilst its on.  Most operate on high voltage and will give you a nasty shock.

I would first look for dry solder joints on the connectors.

Disconnect power, wait for a bit then remove the board.  On the underside of the molex connectors, where they are soldered to the board.  The solder will be dull grey colour if its gone dry and if you wiggle the actual connector, you may see the solder where its broken away from the tracks.

[ddstoys]

Beat me to it Marty  was going to suggest the same.    The buzz noise is most likely to much voltage getting to the display but as marty suggest keep away when it turned on until your confident with what your doin

[necroscope]

Thanks marty,will give it a try,so is the loud hum coming from the board just the high voltage running through it?also i have some solder wick for removing solder would you advise completly removing the old solder and re-soldering or would it be best just to reflow the original,i havent used a soldering iron in years and have never worked on a circut board.

Thanks dd you answered my question while i was posting

[MartyJ]

Thanks marty,will give it a try,so is the loud hum coming from the board just the high voltage running through it?also i have some solder wick for removing solder would you advise completly removing the old solder and re-soldering or would it be best just to reflow the original,i havent used a soldering iron in years and have never worked on a circut board.

Thanks dd you answered my question while i was posting

I am not a big fan of the wick, but I know some others who like it.

For me, I will flow some new solder into it, just to get it flowing nicely, then remove the lot.  Resolder with all new stuff.

[necroscope]

Thanks marty will leave off using the wick as i'm not sure if it would remove any of the track on the board,as i havent had any experience using it before,only got it in case i needed it one day.

[beaky]

if you still have problems after resoldering the pins and when you move the connector it flashes on and off then replace the connector (the one with the wires) and replace the pins or give them a light sand with very fine sand paper.

it could be dry / cracked solder joints or it could be the pins inside the socket that the wires are connected to (some times they loose their grip on the pins that are soldered to the board so they become hot due to the resistance and expand more), or it could be a problem with the connection between wires and the socket. The wires are pushed onto the pins inside the plug when they are made which cuts through the insulation on the wire and contacts the conductor inside the wire.

if you replace the plug on the wires use the molex plugs with the pins that are crimped to the wires not the ones that are pushed on like the one that is on there (use the one on the left in the picture. the one on the right is the original type of connector used from factory)

[necroscope]

Thanks beaky,i'm going to remove the board once i get the wood heater raging,it's so bloody cold here today my fingers are going numb.

[beaky]

Thanks beaky,i'm going to remove the board once i get the wood heater raging,it's so bloody cold here today my fingers are going numb.

try the resoldering first as the other guys have suggested and if it doesn't work then try my suggestion.
And as per what what marty said about the high voltage, he is very right so be careful

[necroscope]

Update,well i removed the board and three of the pins had the solder cracked around the base,so i kind-of heated it up and added a touch more solder as i am a bit scared of going overboard with things like this anyway i replaced the board and so far the displays been running no probs for 20mins,just like to thank you all for the advice and knowledge.

[ddstoys]

Another good result 

[MartyJ]

Very common problem on pinballs and transport never helps!

Just FYI - as mentioned earlier always take super care poking around a machine whilst its on.  Sometimes you can getaway with a small zap, other times cop a big whack or worse.
Not only can you damage yourself, but worse can sometimes the machine!  All you need to do is drop a screw, have a wire exposed and can short lots of stuff...

Good your well on your way to having the machine back up and running.

[necroscope]

I will take that on board marty,i try to always disconnect the power cord before opening the machine and lifting the playfield but i havent been that carefull with the backbox so your advice is well timed,and thanks once again for taking the time to help.

[ddstoys]

A great idea is to get a power cord with a built in safety switch just when working on a machine just a little bit of extra safety

[pinball god]

I've been zapped with the machines off but not disconnected from the wall. Small zaps when accidentally hitting around coil areas. No big deal though