Help with board work

[mickthepin]

I have been trying to figure out a problem with my STTNG. Its the old restart when you flip the flippers problem. I have done what I can do and now its probably going to need some board work. The DC voltage at TP2 on the Power/Driver board is 3.64, DC voltage at the CPU board is 3.64 So there doesn't seem to be any voltage loss across the connectors but this is low. So maybe replacing the LM323K but alot of people say this is a sledge hammer approach, could be the rectifiers or something to do with the caps.
I had just noticed today that the C 3 was detached at one end but i pushed it down so that it was making contact with the board and it doesn't seem to make a difference but.... could this be it?
Any help will be much appreciated.    

[Marty Machine]

What voltage did you measure once C3 was pushed in place?

[pinball god]

You may laugh but I solved the problem via replacing the connector. Can't remember which one that resides on the right vertical side of the power driver. I noticed burn marks on the connector. So check these and if the same replace and see if this solves your problem.

[Marty Machine]

You may laugh but I solved the problem via replacing the connector. Can't remember which one that resides on the right vertical side of the power driver. I noticed burn marks on the connector. So check these and if the same replace and see if this solves your problem.

Yep, burns & corrosion on any pin is a great way to LOSE voltages  ;-(

[mickthepin]

Reset all the cables and no burns or corrosion, the boards are actually in pretty good nic. When C 3 was pushed in place it didn't change the voltage at all. Is this possible?

[Marty Machine]

C3 probably has nothing to do with the +5v supply, hence no change if its in or out, but it's there for another reason either way...

[mickthepin]

Yep I will put it back on but I want to know what I am after before I go taking the board off. Probably beyond me and will have to get a guy in. Any recommendations for someone reliable and not too expensive for western suburbs of Brisbane? 

[wiredoug]

ask http://beakyspinballrepairs.moonfruit.com/

[Crashramp]

ask http://beakyspinballrepairs.moonfruit.com/

+1

[Homepin]

ask http://beakyspinballrepairs.moonfruit.com/

+2

[mickthepin]

Talked to Beaky today and he is going to have a look at the tread. FYI I tested the thermistor in the line filter box between the fuse and the line filter and it read 0.4 Dont know if this means anything. I tried to learn about voltage drop but alot of it is greek to me. I just keep my DMM on the setting that beeps at me and it said  0.4 

[Homepin]

Will Beaky check the "tread" depth to make sure the tyres are legal? 

"beep" is for testing semiconductors (diodes etc) not thermistors.

Just select "ohms" and read what it says BUT it probably won't read correctly as the part needs to be out of circuit to read properly.

[mickthepin]

3.7 I get on 200 ohms setting but like you say still in circuit.
And yes Thread not Tread  

[DSB]

Yep ohms is what you want to measure resistance. Looks like an upside down U. The resistance to current flow with voltage being the pump or pushing force. Simplified a high resistance joint etc. in the circuit will cause a low voltage where you need it. I doubt if the thermistor is faulty. The whole power train needs to be looked at from the 12 volts ac out of the transformer which plugs into the power driver board at j101 and then through the rectification circuit to give you the 5 volts DC and then on to the CPU board. Your problem could be one thing or several things any where along the train contributing to the low voltage. As others have said beaky is your man but you could do some minor testing yourself for interest. Be carefully though as you can cause more trouble for yourself and more expense if you short something on the boards when powered.

[mickthepin]

Yeh I think I will just work on the board when the machine is not on as suggested DBS. Could do more harm than good.