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  #1  
Old 02-14-2016, 07:27 AM
nwkadm nwkadm is offline
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Default Eight Ball Deluxe - High Voltage Issue

I have an EBD LE machine that I was working with to solve a Flickering Display issue. Someone posted that I should check the High Voltage Regulator section for C26 with bad solder joints and to check the voltage at TP2 and TP4. When I check the voltage at TP2, it is 230-240v and the same at TP4 (which I understand is correct). I am being told that TP2 should be around 190v or so and should be adjustable via the Pot on the board. I cannot adjust via the Pot as nothing happens when I turn it right or left.

After resoldering the posts of C26, my flickering display problem was solved but now I still have high voltage at TP2 - any ideas on what to replace would be appreciated.
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Old 02-14-2016, 09:53 AM
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If Q21 or diode CR21 was shorted the regulator might do that. It sounds like the regulator is just passing the rectified and filtered 240V. Does the brightness of the displays dim the more segments are lit? A bad ground back to transformer bridge rectifier might make the regulator float at that high voltage. The voltage divider formed by R54. the 25K Pot. RT1 and R56 is supposed to feed a variable 140 V to the Zener cathode. That is something to check a prove it is varying with the Pot.
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  #3  
Old 02-14-2016, 09:56 AM
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i have repaired the high voltage section on a bally lost world for a friend. it was doing the same thing running wide open with no regulation. it turned out all 3 transistors Q21-Q23 were shorted and they burned out a resistor. when checking transistors for junctions , opens , and shorts you get more accurate readings with the transistors unsoldered from the board. when trying to test transistors in circuit or still soldered in you may get false readings from other parts in the circuit. im not sure what resistor burns up when this happens , but it should be obvious. a pic of the high voltage section may help if you cant find it. after i got the board repaired and installed in the game. i tried to adjust the voltage control pot , only to see the wiper part of the pot fall off. so you may want to change the pot along with your repair. and the little high voltage fuse. the fuse will still hold even if the output does go to 240-250v. it seems like the fuse will blow only when a display short happens.
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Old 02-14-2016, 12:38 PM
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Quote:
Originally Posted by pinballdaveh View Post
i have repaired the high voltage section on a bally lost world for a friend. it was doing the same thing running wide open with no regulation. it turned out all 3 transistors Q21-Q23 were shorted and they burned out a resistor. when checking transistors for junctions , opens , and shorts you get more accurate readings with the transistors unsoldered from the board. when trying to test transistors in circuit or still soldered in you may get false readings from other parts in the circuit. im not sure what resistor burns up when this happens , but it should be obvious. a pic of the high voltage section may help if you cant find it. after i got the board repaired and installed in the game. i tried to adjust the voltage control pot , only to see the wiper part of the pot fall off. so you may want to change the pot along with your repair. and the little high voltage fuse. the fuse will still hold even if the output does go to 240-250v. it seems like the fuse will blow only when a display short happens.

I have taken some measurements and they are as follows (I am an amateur at this):

R35 - .4M
R51 - 200k
R52 - 383
R54 - 8k
R55 - 1200
R56 - 84k
VRi - .6 one direction and OL the other
CR20 - .55 one direction and OL the other
C23 - Beeps in both directions
C26 - .95 one direction and OL the other
C27 - 1.2 one direction and OL the other

Does this tell anybody anything?
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Old 02-14-2016, 02:26 PM
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of what i read on the schematic. R35 should be 100k , R51 should be 22k , the other resistances seem correct. C23 i think should be called C28. testing C28 should not beep in either direction. i see that C28 is across 2 legs of Q23. once Q23 is unsoldered and removed C28 should not beep and when you test Q23 you will see the short. did you unsolder and test the 3 transistors like i asked?
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Old 02-14-2016, 03:39 PM
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Quote:
Originally Posted by pinballdaveh View Post
of what i read on the schematic. R35 should be 100k , R51 should be 22k , the other resistances seem correct. C23 i think should be called C28. testing C28 should not beep in either direction. i see that C28 is across 2 legs of Q23. once Q23 is unsoldered and removed C28 should not beep and when you test Q23 you will see the short. did you unsolder and test the 3 transistors like i asked?



I have not unsoldered those yet - it will be next week before I get to that.
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Old 02-15-2016, 05:06 PM
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I have not unsoldered those yet - it will be next week before I get to that.

Pinballdaveh - I have obtained a list of parts that I have ordered and will replace all of the below:

Q21, Q22, Q23
VR1
CR21
RT1
F1
C26, C27, C28
R35, R51, R52, R54, R55, R56

Thoughts?
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Old 02-17-2016, 04:18 PM
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good picks. that list should cover the problem.
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Old 02-21-2016, 07:15 PM
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Quote:
Originally Posted by pinballdaveh View Post
good picks. that list should cover the problem.

I have replaced all of the components on the above list and my voltage is no what it is supposed to be on TP2 - 190v (I turned it down to 170V per some previous recommendations).

I now see the segments on the 4th players display having a little flickering and the 1st digit goes on and off after it warms up - thoughts on this?
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Old 02-22-2016, 04:17 PM
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Congratulations. Getting that regulator working is very fine indeed. Displays do "Go South" as they age. Their exposure to the excess voltage my have hastened their decline a little. Is that the reason for running them at lower volts, to help them last longer? Do they look better at +190 V's ?
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Old 02-23-2016, 09:55 AM
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Quote:
Originally Posted by Coil_Smoke View Post
Congratulations. Getting that regulator working is very fine indeed. Displays do "Go South" as they age. Their exposure to the excess voltage my have hastened their decline a little. Is that the reason for running them at lower volts, to help them last longer? Do they look better at +190 V's ?

Coil_Smoke - Thanks for the reply - I was told by another source to lower the voltage to prolong the life of the displays. I did not think to raise the voltage to 190v to see how that affects the 4th player display - will try that this weekend.
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Old 02-27-2016, 06:31 AM
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Quote:
Originally Posted by nwkadm View Post
Coil_Smoke - Thanks for the reply - I was told by another source to lower the voltage to prolong the life of the displays. I did not think to raise the voltage to 190v to see how that affects the 4th player display - will try that this weekend.

Coil_Smoke - Raised the voltage to 190v and still have the same issue with the 4th player display - only starts to flicker after 10 or so minutes of play.
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Old 02-28-2016, 06:37 AM
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There is a chance it's a connector issue. Try re-seating the display strobe connectors at both ends. Maybe a little De-Oxit on the headers? I had to fiddle with the ribbon connectors on my Dr. Dude machine. I thought my display was failing. Flickering segments and such. I had to leave a connector cocked sideways to get every segment going.
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Old 02-28-2016, 07:12 AM
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Quote:
Originally Posted by Coil_Smoke View Post
There is a chance it's a connector issue. Try re-seating the display strobe connectors at both ends. Maybe a little De-Oxit on the headers? I had to fiddle with the ribbon connectors on my Dr. Dude machine. I thought my display was failing. Flickering segments and such. I had to leave a connector cocked sideways to get every segment going.

Last night I lowered the voltage to 165v and it took it about an hour to see a slight flicker. I am going to lower it to about 160v today to see what that does.

Thanks Coil_Smoke!
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Old 07-10-2019, 08:46 AM
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Thanks for this thread guys, was having an issue with flickering displays on my Eight Ball Champ game and managed to find out what the issue was with the help of this thread.
Thought I'd leave my issue here for anyone else who manages to find this thread in the future.

Started with measuring the voltage at TP2 which was at 148V, tried adjusting the pot at VR1 but voltage only varied between 144-148V and nowhere near the 190V that was supposed to be there.
Started measuring the components around this circuit and found that the resistor R10 was not letting anything through, replaced R10 and all displays immediately started working again.
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