Electrohome G05-802 Battlezone - No picture

chessiv

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I've have on of these monitors that worked fine and then just went black, not dot etc. Spot killer is not on. Neck board is glowing. Checked all fuses, good. Chassis transistors are good. Pulled D904, which was covered in some stick goop and it appears to be open. I've been through all of the troubleshooting guides and one mentioned you can't actually test these diodes as their reverse voltage is too high.

Thoughts on this? I ordered a cap kit and a replacement diode JIC. The board actually looks pretty clean.

Thanks
 

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Are you hearing any deflection chatter?

The Sticky suggests the following:

Spotkiller is off, I can hear deflection chatter, but have no static on tube face
HV problem. Reflow headers, check F102, replace HV diode.

Monitor has glow, spotkiller off, no deflection chatter
Monitor power problem. Check input power, fuses F100/F101, DB100.
 
I tested the bridge and it's fine. I did find info on how to test a high voltage diode. Supposedly you can check resistance across the diode. The diode read open both ways. So assuming that actually works it's probably the diode.
 
If the spot killer LED is off, and turns back on when you press the reset button on the game board (and stays lit until you release the button), then you have deflection. Chatter is a little harder to hear on these b/w vector monitors, compared to the color ones.

So if you have deflection and neck glow but no picture, the most likely culprit is no HV. You can usually confirm by holding your hand up to the front of the tube. If there is HV, you should feel the static.

If no HV, recap the HV cage and replace the diode. Be sure to clean the 'goop' off of the diode boots (use Goof Off and a bunch of Q-tips). Also make sure the springs and contacts are not rusty, else you'll have a bad connection when you reassemble everything, and the boots will burn up. If they are rusty, you'll need to oak the springs in vinegar overnight and clean them up. Or you can toss the springs and contacts, and solder the diode directly to the wires. (Though you still need the boots to insulate the joints.)
 
Installed the new cap kit and diode. I have high voltage back and an image on the screen. I did have an issue when I re-installed the power transistors on the chassis. One of the mica insulator wasn't in great shape and it shorted the power transistor to the chassis blowing fuse 100+101. Replaced all the mica insulators, checked the transistors to make sure none of them failed and it powers back up. The picture isn't right (see attachments.)

I'm going to take the main board back out and start troubleshooting tonight. Any ideas of where to start based on the pictures?
 

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Did it look any better/different before you blew the fuses?

It souls be game board or monitor. Hard to tell with just that pic. You really need a scope or other good boards to narrow it down.
 
The fuses blew on startup so I didn't get a chance to see a picture. The game worked fine before the monitor went on the fritz.
 
You most likely have blown transistors and possibly other parts as well on the deflection board. You'll have to go through it, as it could be any number of things.

How did you test the bottlecaps?

You can also just trade your dead one in for a rebuilt one, if interested. I have them available. PM for details.
 
I reflowed the connector pins and cleaned the pins themselves and that resolved the issue.

Thanks for the advise.
 
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