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Game is restricted to the lower right corner of the Screen.
Repair of: Monitor (Wells Gardner WG6100)
Repair Type: Part
Status: Fixed
Contributed by: Arcadenut
Symptom:
After rebuilding my 6100 for Tempest, I encountered this new issue where the you could see the full game, but it was in the lower right corner of the monitor.  It appears to have full deflection, but it doesn't fill the entire screen.
   
Solution:
Had a bad LV2000.  The nice thing about the LV2000 is they will replace it for free if it ever goes bad.  Just luck of the draw that I had a bad one.  Still highly recommended.
 
The main problem was is it wasn't putting out the proper voltage to the HV section.  The HV section needs +26V DC and -26V DC,  the the LV2000 was only putting out the +26V DC so the monitor was drawing the entire image in the lower right corner.
 
So if you don't have an LV2000 installed, then the problem is in the Low Voltage section and either fixing the low voltage section, or by upgrading to an LV2000 it will fix this issue.
 
 

Diagnostic/Repair Steps

 
The following steps were taken to either diagnose or to repair the PCB/Part/Game: 
Checking the LV2000
3/4/2013 4:19:33 PM
I upgrade the monitor with an LV2000.  The LV2000 has two LED's on it that should be lit when the monitor is functioning correctly (at least for the power section).  In this case only the left one is lit. 
Testing Voltages at P100
3/4/2013 4:21:16 PM
Yes, it makes me nervous sticking my hand in a live monitor... but you have to do it.
 
P100 connects the Deflection board to two of the four transistors under the frame.  According to the manual for the LV2000, pin 6 should have around -26VDC and pin 3 should have around +26VDC.  As long as you're close, it should be ok.
 
In this case, I had the -26VDC on pin 6, but had close to 0 on pin 3.   So something is pulling that voltage down and I need to track that down.   That will be the next step.
More Testing
3/9/2013 4:34:52 PM
Ok, Started by Disconnecting P600 to see if it affected the LV2000.  It did not.
Now P700
3/9/2013 4:38:35 PM
Then I reconnected P600 and disconnected P700.  Same Results.  Right hand light on the LV2000 goes out.
 
Currently they both stay on if I disconnect P100, but I've replaced both of those transistors TWICE and no luck.
Voltage Readings
3/9/2013 5:07:15 PM
Ok, decided to go back and recheck all my voltages and document them here a little better.
 
With P100 disconnected, and everything else connected:
Pin   Expected  Actual
 1 +33V DC +33V DC
 2 Not Connected Not Connected
 3 ~ +25V DC +26V DC
 4 ~ +25V DC +26V DC 
 5 ~ -25V DC  +8V DC
 6 ~ -25V DC  -26V DC 
 7 -33V DC  -33V DC
 
As you can see Pin 5 is WAY wrong.  What's even stranger is, that Pin 5 should be a NEGATIVE voltage, but it's Positive!
 
After disconnecting P700 and P600, here are the results I got: 
Pin   Expected  Actual
 1 +33V DC +33V DC
 2 Not Connected Not Connected
 3 ~ +25V DC +26V DC
 4 ~ +25V DC +26V DC 
 5 ~ -25V DC  +15V DC
 6 ~ -25V DC  -26V DC 
 7 -33V DC  -33V DC
 
We're getting closer, so something else further down in that circuit appears to be pulling the voltage down. 
 
Now I disconnected P101 and the voltage dropped to 0! 
Pin   Expected  Actual
 1 +33V DC +33V DC
 2 Not Connected Not Connected
 3 ~ +25V DC +26V DC
 4 ~ +25V DC +26V DC 
 5 ~ -25V DC  +0V DC
 6 ~ -25V DC  -26V DC 
 7 -33V DC  -33V DC
 
Not what I would have expected to happen... but it could be related to the +/- Voltage issue too.  Will have to look at the HV section and see what that is connected to.
 
 
P900 Connector (and B+)
3/9/2013 5:59:23 PM
Time to check the B+ and other voltages related to that.
 
With everything connected:
Pin   Expected  Actual
 1 +27V DC 0V DC
 2 +27V DC 0V DC
 3 GND GND
 4 Not Connected Not Connected
 5 181V DC +80V DC
 6 Not Connected
Not Connected
 7 -27V DC -24V DC
 8Not ConnectedNot Connected
Since Pins 1 & 2 are 0V, I don't want to mess with the B+ until I figure out why that is. 
It's fixed!
3/17/2013 3:37:19 PM
Replaced the LV2000 with a new one I received and it now works!  Woohoo!
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