Arcade game monitor problem

rec.games.video.arcade.collecting is the correct newsgroup.

On Wed, 22 Oct 2008 08:22:07 -0600, snipped-for-privacy@webtv.net (Ken G.) put finger to keyboard and composed:

The "blooming" does sound to me like a low EHT problem. I'd check the B+ going to the FBT, and the base drive to the LOP transistor. Make sure the duty cycle doesn't change. I've seen this happen in an old IBM monitor as a ceramic capacitor in the horizontal oscillator warmed up. However, in my case the EHT gradually increased until the HV protection shut down the monitor.

- Franc Zabkar

Thanks Franc .. I dont know which conection is B+ on this . It seems to be a Wells Gardner monitor according to a website provided i an arcade newsgroup .

This is an XY monitor, the scan is very different compared to a normal tv.

Try this Page

The fault sounds like b+ is going low, maybe a bad cap in power supply. I think from memory its 123v to HT Generator Board.

On Fri, 24 Oct 2008 08:33:20 -0600, snipped-for-privacy@webtv.net (Ken G.) put finger to keyboard and composed:

I would think that one end of the primary winding would be connected to the collector of the switching transistor, the other to the B+.

If the FBT has any part numbers, try locating a substitute here:

The HR substitute will have a wiring diagram with voltages.

I notice that the Wells Gardner Quadrascan colour monitor at the Atari link provided by Dean uses a HV regulator circuit that senses a 180V pulse from a tap on the primary winding and uses this feedback to vary the B+ to the FBT, and thereby control the EHT.

- Franc Zabkar

Sounds to me, more like the Filament Voltage is dropping, cold solder joint in filament circuit ?

This describes what happens to the image when I reduce the filament Voltage on my Transmission Electron Microscope !

Yukio YANO

Your _own_ TEM? Really! Do you have photos of it on a site somewhere?

Michael