Help with 19K4915

[Grauwulf]

Okay, I'm stumped with this monitor now. I have followed the troubleshooting flowchart from Randy Fromm's website and I still can't get this monitor working. Just a brief history on what I have found so far. Flyback was melted, and had melted some of the wiring going to the neckboard. Also the HOT was not the right one. Someone had put a D1398 in place of the D870 that was supposed to be in there. So I have swapped on a flyback from another 4900 series monitor I have (unknown if working or not, but visibly fine), installed the correct HOT (new) and replaced the melted wiring going to the neckboard. Powered it up and it sounds like a normal monitor powering up, but the heater does not glow. Checked B+ voltage and I have 165v at both ends of R503. Jumpers and traces going to the HOT are fine, and I have 165v at the case of the HOT. I have tested Q351 and swapped in another one that also tested good. Checked R363 and it is showing the correct resistance. I have also swapped IC301 for another one (unknown though) and I still have the same conditions, 165v across the board. What are the chances both of the IC301 chips are bad? Is there anything else I can check? Where do i go from here?

[Ken Layton]

Is IC501 (STR 360) voltage regulator bad?

[Grauwulf]

I wondered that (it lists a STR380 on my schematics) but following Randy's flowchart because I'm seeing 165v, it leads over to a horizontal deflection failure instead of a voltage regulator problem. That's why I'm confused.

[fredster]

Tube fried?
Blanking circuit dead?

[Ken Layton]

The regulator can short or go leaky and cause the B+ voltage to go way up which triggers the shutdown circuit.

[Grauwulf]

Well Ken, it looks like you win the prize! I put a new voltage regulator on the board tonight and I get that nice orange glow in the neck of the monitor. I'm still a little concerned that the input voltage into the regulator is a little higher than it should be. But we'll see if it is actually working properly when I put it back in the cab tomorrow. I'll let you guys know what the final result is.

[Grauwulf]

Well it looks like the monitor is fixed. Mow I get to fix the game board. All I'm getting is garbage, but if you coin up it makes the right noises. So now I get to dive into the game boards. Thanks for everyones help!