Dragon's Lair Fans - Arcade Lifestyle

General Chat => Technical Area => Topic started by: rogerxy on February 19, 2017, 04:52:09 PM

Title: G07 low B+
Post by: rogerxy on February 19, 2017, 04:52:09 PM

Hi!
Bought a G07 who seem to be completely dead. Recapped it as well as change of the flyback & the parts kit from Ian Kellog.

Now it's alive! However, the B+ is too low (should be 120)

First it was 113,7 when the G+ pot was turned all the way. I got a few tips & checked the resistors R908, R912 & FR901, they are all good.
The filter cap shows 612uF. Should be 680uF but I guess that's fine(?)

I also changed the B+ pot with a pot from a spare G07.

Now it shows 118,2V so quite an improvement. But is it good enough? Since I'm kinda new to all this I'm not quite sure what a low B+ can lead too & what the accepted error range is.

Title: Re: G07 low B+
Post by: Pinge on February 19, 2017, 05:52:17 PM

On Klov I found this info about B+

Quote

It's important that the B+ be set correctly. Running it too high will result in a picture that's too large, and could cause the monitor to go into shutdown to prevent the HV from going high enough to generate X-rays through the picture tube. Too low can cause a small picture, waves of distortion in the screen, or image instability.

https://forums.arcade-museum.com/showthread.php?t=143645

So I guess if you dont get a small picture, waves of distortion or image instability your B+ is not to low.
But I understand you want to dial it in exactly

Title: Re: G07 low B+
Post by: level42 on February 19, 2017, 06:41:45 PM

0,8V on a value of 120V is nothing. If the picture is fine I don't see a problem.