G05-802 Develops "Ring and Dot" at center after a few minutes.

tta583

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G05-802 Develops "Ring and Dot" at center after a few minutes.

I am putting together 2 Asteroids back to back. Both have a G05-802. Both re-caped, diodes cleaned, new deflection transistors. More or less, the works. Both have great displays. One, however, develops a slight dot in the center after a minute or two. Very faint. About 4 minutes in or so it becomes a ring, about 3/4 the size of a dime, with the original dot in the middle. It's pretty apparent its the beam crossing through the center. No amount of brightness or contrast adjustment prevents it from occurring. I thought it may be in the Z amp so I swapped in the the other deflection board. Same thing. Not sure if it could be anything in the HV can. I did look at the voltage at the anode cup. Solid on 12KV. It was getting late so I did not look at the other monitor yet or go much father in looking things over.

Anyone ran into this? Some Google searches earlier turned up other instances but no good leads. At least none I found.
 
Forgot, I did swap game boards thinking I may have something odd going on in the Z section there. No luck. Same deal.
 
The couple times I've ran in to this........it was the tube. Got a space you could swap to confirm?

Edward
 
Yeah, I have space. Are you suggesting yokes swap or stay with the frame? If I move the high voltage can over I have almost made a swap save for the yoke and deflection transistors.
 
I am putting together 2 Asteroids back to back. Both have a G05-802. Both re-caped, diodes cleaned, new deflection transistors. More or less, the works. Both have great displays. One, however, develops a slight dot in the center after a minute or two. Very faint. About 4 minutes in or so it becomes a ring, about 3/4 the size of a dime, with the original dot in the middle. It's pretty apparent its the beam crossing through the center. No amount of brightness or contrast adjustment prevents it from occurring. I thought it may be in the Z amp so I swapped in the the other deflection board. Same thing. Not sure if it could be anything in the HV can. I did look at the voltage at the anode cup. Solid on 12KV. It was getting late so I did not look at the other monitor yet or go much father in looking things over.

Anyone ran into this? Some Google searches earlier turned up other instances but no good leads. At least none I found.

I have the same issue and so far is unresolved. Is your Spot Killer light on? I have an issue with mine as well that even though I have 100% deflection, the Spot Killer light is on.

Was trying to fix that before the dot issue as I didn't want to be chasing something that wasn't an issue if it was related to that issue.
 
I have the same issue and so far is unresolved. Is your Spot Killer light on? I have an issue with mine as well that even though I have 100% deflection, the Spot Killer light is on.

Was trying to fix that before the dot issue as I didn't want to be chasing something that wasn't an issue if it was related to that issue.

Is your spot killer always on?.....or does it go on and off?

Edward
 
One, however, develops a slight dot in the center after a minute or two. Very faint. About 4 minutes in or so it becomes a ring, about 3/4 the size of a dime, with the original dot in the middle. It's pretty apparent its the beam crossing through the center. No amount of brightness or contrast adjustment prevents it from occurring. I thought it may be in the Z amp so I swapped in the the other deflection board. Same thing. Not sure if it could be anything in the HV can. I did look at the voltage at the anode cup. Solid on 12KV. It was getting late so I did not look at the other monitor yet or go much father in looking things over.

You're there!

The portal is opening!

Increase the power and stand RIGHT IN FRONT!!
 
It's always on. I've replaced pretty much everything in the Spot Killer section, minus the silver cap (don't remember it's value right off hand).

This will happen if Q502 is installed backwards. Everything will be prefectly normal and operate 100%......but the spot killer LED will stay lit.

Edward
 
This will happen if Q502 is installed backwards. Everything will be prefectly normal and operate 100%......but the spot killer LED will stay lit.

Edward

My board doesn't seem to have a Q502... :confused:

EDIT: Ok, the G05-802 has a Q502, however mine is a G05-801, which does not have a Q502.
 
Last edited:
My board doesn't seem to have a Q502... :confused:

EDIT: Ok, the G05-802 has a Q502, however mine is a G05-801, which does not have a Q502.

Oh, sorry.....the -801 is a little different. I'd double check the three transistorts in the spot killer circuit for proper orientation (Q503, Q504, Q506). Might get lucky.

Edward
 
You're there!

The portal is opening!

Increase the power and stand RIGHT IN FRONT!!

Will do...upping the high voltage.....have to get it big enough to crawl through....
 
This will happen if Q502 is installed backwards. Everything will be prefectly normal and operate 100%......but the spot killer LED will stay lit.

Edward

That was it. In this case it was Q503 and Q506. The E and C are backwards on the PN3569 compared to the TIS98 that was in there before.

Thanks!
 
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