Xenon
Bally, 1980All -
Putting the finishing touches on Xenon resto. Have the rectifier back in and checking voltages before putting brand new boards in (so want to make sure everything is spot on).
Everything looks good except for TP3 - I am getting a rock solid 34.6vdc on what should read 11.9 or thereabouts (from what I have read 14v is actually good). R1 and R2 are fine. This is a stock board. There is no load on the output.
ideas? This seems very high to me even though it is unregulated.
Thanks -
-scott
Also, the diodes seem to be in spec with each other...
CR5 measures .482
CR6 = .485
CR7 = .486
CR8 = .482
-scott
Those measurements look ok.
And TP3 is still measuring high?
It doesn't make any sense that the DC output can be more than twice the voltage coming in. Did you do any repair work on the rectifier board? A leakage short to the 43V line maybe??
Nothing done at all. The game would not boot when I got it, and J5 was burned in two at pin 12 for the SDB (orange wire). All that has been replaced and I have new boards, but have not plugged anything in beyond the primary from the transformer.
All other voltages seem dead on on the rectifier - if it were "leaking" to the 43v bus would that not show up there as well?
I did read somewhere that it has been noted that unloaded that voltage can read very high - just makes me nervous plugging a brand new board it. I tried to look up specs on the Alltek to see what the max input voltage for the 12v line would be but no luck.
-scott
I presume you only have J5 and J6 connected on the rectifier board? i.e. J1, J2, J3 and J4 are not connected?
In this condition on my game with a -54 board (but not a Xenon), I get 13.9VAC at the points circled in the above diagram out of the transformer, and 13.8VDC at TP3 (i.e. unloaded) with the black meter lead on the "GND" TP terminal on the rectifier board.
With J1, J2, J3 and J4 disconnected, you may not have a proper ground reference in the chassis with respect to the rectifier board. So if you're putting the black meter lead somewhere on the metal chassis your ground reference might be out.
Quoted from drscottsmith:Have the rectifier back in and checking voltages before putting brand new boards in (so want to make sure everything is spot on). Everything looks good except for TP3
Quoted from drscottsmith:All other voltages seem dead on on the rectifier
These two comments seem contradictory. Are the other voltages on the rectifier board ok or not?
I was using the GND TP on the rectifier board as the ground point. Board is in the machine (e.g. not on bench) with grounding braid installed.
J1-J4 are disconnected. I suppose I could plug them in to the rectifier board and leave them unplugged in the backbox.
I did not check the voltage at the connector that sends power to the backbox (I believe its J3). I cant imagine there would be any chnge between the TP and the output line.
To clarify the contradiction (I can't remember the exact numbers):
TP1 ~ 8vdc
TP2 ~ 185vdc
TP3 ~ 34.6 vdc
TP4 ~ 7.6vdc
TP5 ~ 46vdc
Everything looks good to me except TP3...thanks for all of your help on this, btw.
-scott
There is not resistor at all to add load. The VDC reading will probably shoot up. Check out the hv section. There is a resistor in series with the test point. Other voltages have power resistors to add load and keep vdc stable.
You are probably fine to plug in the top right connector of the SDB.
Unloaded, I measure 13.8VDC with my multimeter. And unloaded using my oscilloscope, I measure a *peak* voltage of 20VDC.
I can't see any way it can go up to 34VDC in this simple DC rectifier setup - especially since the other unloaded voltages are somewhere within range.
BTW at TP4 you should be measuring 0VDC. It is an AC circuit and there is no DC rectification, so you should measure ~6.5VAC
Put a load on that 11.9VDC line. Connect something like a 12V small car lamp between GND and TP3, then measure the DC voltage at TP3.
Quoted from Quench:Unloaded, I measure 13.8VDC with my multimeter. And unloaded using my oscilloscope, I measure a *peak* voltage of 20VDC.
I can't see any way it can go up to 34VDC in this simple DC rectifier setup - especially since the other unloaded voltages are somewhere within range.
BTW at TP4 you should be measuring 0VDC. It is an AC circuit and there is no DC rectification, so you should measure ~6.5VAC
Put a load on that 11.9VDC line. Connect something like a 12V small car lamp between GND and TP3, then measure the DC voltage at TP3.
low end meters can have trouble when there is no load.
Scott,
I had the same problem on my Stern except I was reading 57 VDC. Barakandl told me once it was loaded it will stabilize. He was right. It worked fine.
See this thread:
https://pinside.com/pinball/forum/topic/bad-meter-%E2%80%93-bad-voltage-%E2%80%93-or-bad-technician
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Duncan, SC