New to Pinball Info and looking for direction.

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Thehipster

Thehipster

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Joe
That's great. Repeat the check including pin8 once you have replaced the resistor then as it is important that the 170V is regulating correctly before the displays get connected.
Well I surpised myself with some neat soldering (considering I have never fitted anything onto a board before) and the resistor is on the board and number 8 pin reads 150v.
 

Zaccaria Keith

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Keith Withnall
Well done. That voltage is rather low so I think we need to investigate further as other components may have been damaged by the short circuit. Proceed carefully as these DC voltages can give you a nasty jolt if you touch them. Measure the voltage across C1 - the largish 100uF 350V capacitor below R6.
 
OP
Thehipster

Thehipster

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Joe
Well done. That voltage is rather low so I think we need to investigate further as other components may have been damaged by the short circuit. Proceed carefully as these DC voltages can give you a nasty jolt if you touch them. Measure the voltage across C1 - the largish 100uF 350V capacitor below R6.
So is that a probe on each leg and VAC?
 

Zaccaria Keith

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Keith Withnall
Also when you measured the voltage on Pin 8 of CN5 can you confirm that you had the meter set to measure DC voltage and not AC voltage
 
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Thehipster

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Joe
Also when you measured the voltage on Pin 8 of CN5 can you confirm that you had the meter set to measure DC voltage and not AC voltage
Yes the straight line above a dotted line. Not ac with a wavy line?
Also the capacitor is a replacement and is sitting to the right of the position it should be in and a wire goes from the capacitor to the other side of the position marker. I tried to photo it but my laptop is not allowing me to download it. I could mail it to you.
 

Zaccaria Keith

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Keith Withnall
That sounds correct for the DC meter position. If you can't get onto both leads of the replacement C1 easily, then put the negative probe lead onto one of the screw heads at the bottom of the board again and put the red lead onto the lead that goes across from the left side of the replacement capacitor. You are looking for about 230V
 
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Joe
That sounds correct for the DC meter position. If you can't get onto both leads of the replacement C1 easily, then put the negative probe lead onto one of the screw heads at the bottom of the board again and put the red lead onto the lead that goes across from the left side of the replacement capacitor. You are looking for about 230V
Yep. 223v
 

Zaccaria Keith

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Keith Withnall
OK it sounds like the rectifier bridge has survived. Now measure the DC voltage across the ends of R10 which is just below the 170V heatsink on the right side of the board
 

Zaccaria Keith

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Keith Withnall
That's rather low. Measure the voltage with a probe on each end of D21 and then D22 - we are expecting about 75V DC across each. They are just to the left of R10 and the end with the stripe will be positive.
 

Zaccaria Keith

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Keith Withnall
OK, one final measurement then. put the probes on each end of R9 - this will be a much lower voltage - we are expecting around 0.6V DC
 

Zaccaria Keith

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Keith Withnall
OK. Please could you try it again as the probes might not have been getting a good contact with the legs of the resistor. It doesn't make sense for that to be zero
 

Zaccaria Keith

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Keith Withnall
No it's black to the right definitely. Try with the black probe on the screw head at the bottom of the board and the red probe on the right hand end of D21 (the end without a stripe), must be D21 and not D22.
 
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Thehipster

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Joe
No it's black to the right definitely. Try with the black probe on the screw head at the bottom of the board and the red probe on the right hand end of D21 (the end without a stripe), must be D21 and not D22.
That reads 0.00 also. When I read it with the black on the left of the d21 and the red on the right it reads 65v dc.
 
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Zaccaria Keith

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Keith Withnall
That implies a base-emitter short in TR3 which would normally result in the output voltage being way too high, but your 170V regulator appears to be working but just a little bit low in voltage, and the actual output voltage agrees with the voltages across the zener diodes that provide the reference for the regulator. Please could you increase the voltage range on the meter again and measure the dc voltage between the screw head at the bottom of the board (black probe) and the top end of R3 (next to R6) with the red probe. Expecting about 153V DC
 
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Thehipster

Thehipster

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Joe
That implies a base-emitter short in TR3 which would normally result in the output voltage being way too high, but your 170V regulator appears to be working but just a little bit low in voltage, and the actual output voltage agrees with the voltages across the zener diodes that provide the reference for the regulator. Please could you increase the voltage range on the meter again and measure the dc voltage between the screw head at the bottom of the board (black probe) and the top end of R3 (next to R6) with the red probe. Expecting about 153V DC
It measures 1.88 vdc with the metre at 200v
 

Zaccaria Keith

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Keith Withnall
Up until those last two measurements I thought that your 170V supply was basically working, but now it looks like the transistors have been blown and we are just seeing enough current leakage with no load to develop voltage across the zener diodes. I think we need to measure it with some load on it.

With the power off unplug the bottom section of the CN6 connector on the sound card (it goes on pins 1 to 4). This will remove all power from the sound board as that may have been damaged by the original problem. Reconnect CN5, making sure the alignment is right then power up and immediately measure the voltage between the screw head and pin 8 of CN5 again and see what it is. If more than 170V then switch off immediately, otherwise you can recheck the other voltages on CN5 like you did earlier to make sure they are still in the range I specified and see whether you have any displays and whether any of the game works before turning off and reporting back.