Asteroids G05-802 - Occasional Spiderwebs flareup - Man I'm tired of working on this - HELP!

gameroommedic

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Hey all. So my experience with CRT repair is not extensive but I HAVE enjoyed some successes. Picked up this asteroids last year. Good board, I recapped, and was serviced by Eugene Marsh. I also recapped the deflector board and installed the jumpers in place of the 2 wirewound resistors. All good there, so it seems.

In the HV cage I have replaced cleaned/reflowed the connector pins and the 2 transistor sockets. Replaced the caps, zeners and HV diode and the tropical fish capacitor.

Upon power up, I start out with +90v at pin 1 of P500... but after about 12 minutes it has risen to 91.8 volts, and this is when the spider webs begin intermittently appearing. Fiddling with the brightness pot makes this stop to a degree, however I had previously removed and cleaned both brightness and contrast pots. Seems to electrically function properly when connected to ohmmeter and turned.

I have to have brightness set lower than normal to eventually get ideal level after about 15 minutes. I KNOW this isn't right. And even after that I get occasional spider web flareups. I hesitate to let my friend have the game.

With all these associated parts I have replaced... what could be wrong?? Wayne Hamilton in Oz has made great efforts to help me during this.
 
Yes, this has been a struggle to get thy head around the problem,
typically it is only those few parts you have replaced..
i have a similar problem with a G05-801 cage & starting to think my problem could be the fly-back ?

i'll tap @andrewb in to your thread, he will know :)
 
I wouldn't suspect the flyback. A flyback issue would result in blooming, not brightness issues.

If fiddling with the pot changes anything, I'd be suspicious of something else on the deflection board. Possibly a cracked trace, which isn't uncommon on these, especially around the headers. (I'd also just replace those pots, if you suspect they could be the problem, as the old pots can be flaky sometimes.)

Easiest thing would be to swap the deflection board out with another known-good one, to really pinpoint where the issue is, as there are other things that can cause it. But if you can isolate the issue, you can save yourself a lot of time. See this thread for a list of other things it could be:


But in this case I'd closely inspect the area around the brightness can contrast pots, as that's the Z circuitry area. Also look for cracked traces where the traces meet the header pins, for the P500 header. (And note that traces can be cracked in ways you can't easily see with the naked eye, especially when the crack happens right where the trace meets the solder, which reflowing the solder alone won't fix.)

Also, pull the P500 header connector and look inside it, at the contacts. Shine a light inside. The contacts should all line up with each other, in a straight line. Make sure none are pressed in or bent at all.

Also, get some DeOxit D5S, and use it on every connector in the cabinet, including the tube socket. Dirty contacts can cause all sorts of issues.

And lastly, check to see if your deflection board has the R100/101 resistors. If so, they should be removed. And see this thread for other brightness-related issues that can result:


If all else fails, your tube might just be tired, or have an internal short. But there's a lot of other stuff it could be before that, and you have to rule them all out first.
 
I wouldn't suspect the flyback. A flyback issue would result in blooming, not brightness issues.

If fiddling with the pot changes anything, I'd be suspicious of something else on the deflection board. Possibly a cracked trace, which isn't uncommon on these, especially around the headers. (I'd also just replace those pots, if you suspect they could be the problem, as the old pots can be flaky sometimes.)

Easiest thing would be to swap the deflection board out with another known-good one, to really pinpoint where the issue is, as there are other things that can cause it. But if you can isolate the issue, you can save yourself a lot of time. See this thread for a list of other things it could be:


But in this case I'd closely inspect the area around the brightness can contrast pots, as that's the Z circuitry area. Also look for cracked traces where the traces meet the header pins, for the P500 header. (And note that traces can be cracked in ways you can't easily see with the naked eye, especially when the crack happens right where the trace meets the solder, which reflowing the solder alone won't fix.)

Also, pull the P500 header connector and look inside it, at the contacts. Shine a light inside. The contacts should all line up with each other, in a straight line. Make sure none are pressed in or bent at all.

Also, get some DeOxit D5S, and use it on every connector in the cabinet, including the tube socket. Dirty contacts can cause all sorts of issues.

And lastly, check to see if your deflection board has the R100/101 resistors. If so, they should be removed. And see this thread for other brightness-related issues that can result:


If all else fails, your tube might just be tired, or have an internal short. But there's a lot of other stuff it could be before that, and you have to rule them all out first.
Thank you Andrew. The resistors HAVE been removed and jumpered. I had also replaced the associated transistors on the deflection board during this journey. I'll perform the inspections/cleanings you suggest. WHERE can I get those larger style pots for brightness/contrast? Everything I find is way too small.
 
Thank you Andrew. The resistors HAVE been removed and jumpered. I had also replaced the associated transistors on the deflection board during this journey. I'll perform the inspections/cleanings you suggest. WHERE can I get those larger style pots for brightness/contrast? Everything I find is way too small.


APAR.


 
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