WG6100 258v at p900 pin 5

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Hey guys. I am working on a gravitar I just bought. It was dead when I bought it, plays blind. I replaced the flyback and got HV back and now have the birght dot in the center. While troubleshooting I checked pin 5 on the p900 and got 258v. Pin 1 is around 26v and pin 8 is around 15v (supposed to be -28?)

Any ideads?

-Ken
 
I have not tried to mess with that pot. If I do mess with it, how do I adjust it back to nominal? I ask because there is a new one in the kit of parts I ordered from Bob Roberts. I am about done installing bazillion parts in the kit but thought if anyone had seen that issue before I could be sure I replaced it before plugging it all back in.

-Ken
 
You stated you just bought this. You have no prior insight to who did what on that machine so seeing the voltages out of whack wouldn't suprise me in the least. Also the pots get crispy - you need to replace it.
Anytime you replace a flyback you need to adjust the b+
http://www.ataricade.com/WG_6100_FAQ.pdf <-- page 33
http://www.arcadeshop.com/wgxy-fb/wg_install.pdf
See page 8 - does your HV board have one? Some had the HV trip pot and some didn't
 
Turn the new pot all the way down (counterclockwise) then turn it up slowly while measuring it...
 
Ok, so a ton of parts later and countless hours and I have the same issue. When I turn the new pot I installed I can adjust out about 5v but still in the 250v range. Any ideas?

-Ken
 
there's a resistor on the deflection board, R612, that if it goes bad, it can cause this...
 
I'll give that a look after I get the problem I just caused fixed. I think I tried to discharg the anode while it was powered on, that or unpluging p100 while it was on did it. I cannot imagine how I had it on and tried to discharge it and did not hear a huge POP but I dont remember truning it back on before I put p100 back on while powered up. At any rate I have no more HV and only 25v and P900 pin 5 now... Oigh I am about done working on this silly thing!
 
At this point I have NO HV and I have a chassis short to Q103. I suspect i blew something when I hot pluged the p100 connector. Is there a common failure here I should pick up while I am out today? D104 and D105 look quite a bit different than the ones they replaced and I read somewhere that the ones in the bob roberts kit were not up to the task.
 
The difference in appearance of an item is highly likely but as long as it specs out the same (or higher in voltage in some instances) it doesn't matter. For instance if you have a 220ohm 16v cap you could replace it with a 220ohm 30v cap. Zanen and Bob Roberts kits are based on the old parts list which is too bad really. There is info out there that lists parts that should be upgraded. <-- that and adding a LV6100/LV2000 always come up for debate.
Q103 being in the LV section - can we assume the LED on the deflection board is on now?
 
Ah geez that sucks. I can check at home tonight and see if I have one laying around or you can call down to NORVAC and see if they have any. Me personally I now add a LV6100 or LV2000 to any K6100 I work on. It's cheap insurance.
Have you tested out the surface mount transistor to ensure that isn;t blown? I might have one of those in my crap pile ;)
 
I have another 3792 I can swap with, I am pretty sure I blew the diodes when I plugged p100 in hot.

What I would really like to know is what can cause pin 5 of p900 to be 250+v when I do have HV. I will be repalceing the parts to get HV back up soon then i'll be back to square 1. The condition of the board is unknown so maybe its a board issue.

-Ken
 
I don't know why the HV would be so far out of spec. All I can recommend that is you pull a leg on every component and meter them out. If they all check out.........

There are 3 things on that board that can't be easily checked. You already replaced the flyback so the next step is the 555 CMOS timer chip. Radioshack carries them.
And FWIW - the last time I went there they had the old part number superceded .... the new one works just the same
http://www.radioshack.com/product/index.jsp?productId=2062595
 
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Well, I got HV back, I tested all the diodes around the p100 connector, all checked good. Checked the 2n3792 it was good, but it all back together and have HV again but still spot killer light and 250v at pin 5 and 15v at pin 8. John will be down tomorrow and hopfully we can figure it out then.

-Ken
 
Unfortunatley Bob Roberts doesn't provide a breakdown list of the parts in the kit. Does it come with a C905 cap?
Double check on the HV board that you have installed MPS-A06's at Q901, Q902 and Q904 <-- usually you won't get the crackle or static sound when these are bad
Q903 requires 2N3904 <-- I've had some in hand that had a MPS-A06 instead

If everything checks out I think you should replace the 555.
Do you own a HV probe? It'd be helpful
HV Voltage Range Look at
??.?-12.0 kV Q902 (reversed)
7.0-10.0 kV ZD902 (bad)
7.0-17.0 kV ZD902 (bad)
7.0-22.0 kV Q903 (bad)
9.0-18.0 kV ZD902 (bad)
11.0-22.0 kV ZD902 (bad)
15.0-18.0 kV ZD901 (wrong value)
16.0-19.0 kV ZD902 (bad)
18.0-27.0 kV ZD902 (bad)
19.0-27.0 kV R912 (wrong value)
21.7-30.5 kV C916 (open)
28.0-20.0 kV C916 (bad)
 
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