WG6100: Bob Roberts cap kit done, now ZD902 blown open!

MajorHavoc

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WG6100: Bob Roberts cap kit done, now ZD902 blown open!

Did not read this warning in 6100 FAQ until after I applied power! :-(

R918 25k Pot
Do not install unless necessary: pre-
adjust to 5.5k ohms on the upper 2
contacts

So, I will order replacement ZD902. What else should I check/replace?
 
Can someone illuminate what the FAQ means by "when testing the upper two contacts of the three" in the following statement? Upper relative to what? Or just tell me what test points to use when measuring for 5.5K?

Thanks!

R918 needs to start out adjusted to an in-circuit resistance of 5.5K when testing the upper two contacts of the three.
 
Can someone illuminate what the FAQ means by "when testing the upper two contacts of the three" in the following statement? Upper relative to what? Or just tell me what test points to use when measuring for 5.5K?

Thanks!

R918 needs to start out adjusted to an in-circuit resistance of 5.5K when testing the upper two contacts of the three.
I had a hard time adjusting my R918 pot as well. Here's a thread where I got some pointers on pre-setting it. Was yours cranked way high? It doesn't seem like having it low would kill anything.

http://forums.arcade-museum.com/showthread.php?t=222106
 
Replaced ZD902 and C902. Dialed in R918 measuring the two points closest to Q903 (base of Q903 to R911).

Power up, and no HV. :( Spot killer off, both LEDs lit on LV2000, and I hear vector chatter.

Any short-cut methods to find the problem?
 
Do you have a scope with X-Y inputs? Could be a board issue. Have you adjusted the brightness?
 
Do you have a scope with X-Y inputs? Could be a board issue. Have you adjusted the brightness?

1) I do. Was using it to display some Atari vectors this evening.
2) No. It's definitely in the HV cage because I can swap in a known working and the monitor works.
3) Yes.

Thanks for the response!
 
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