pacman WG 19k7901 no image, HV

pinnut

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first rodeo with a wg7000. ps- this unit has a remote board for adjustments. no image, no heater glow. when first turned on, there is a slight screen crackle, then no HV. chassis fuse good. my first suspicion is xray shutdown. i took the chassis home. i have a good tube from a pacman with a GO7. first can i use that tube with this chassis for testing? 2, there is a flow chart in the WG manual, but is there anything better? 3. where would you start with this? i checked the str3123 regulator. no pins shorted to each other, or to ground.pin 3 is to ground, as per schematic. it has 5 pins, but the 5th is cut off, and a blue wire comes from the pin 5 position on the PCB and goes to the large white ceramic resistor on the side . can i check B+ there, 123 v? there is a sticker says it was worked on in 1998. there is a rather crude hole in the pcb, see pic. if that a mod? thanks
 

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update. pulled the hot( which tests good), and checked the b+ voltage using a lamp as a load. dead nuts on at 122.5v. stays that way while dialing the variac up and down. dont see any bad solder joints. checked the tube cup HV. when you turn it on, goes to 14kv, then it drops from there quickly down to zero. off and back on, does the same thing. hard to say if it was ever recapped. does look like LA7831 was replaced. caps are all daewoo brand. any ideas? thanks
 
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