G05-801 questions and curiosities

PumRibby

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This is the first 801 I am working on out of a Lunar Lander. It's on loan to our Arcade if I can get it fixed. The fuses at F100 and F101 were blown when I got it so I decided to do a cap kit and check the bottle cap transistors first before I just put the fuses back in and powered it up. After I finished, powered it up and F101 blew instantly. I checked the bridge rectifier at DB100, after seeing a post about it and watching dokert's video on testing one to make sure I was doing it right, and there is a short in one of the directions. So my main question is:

Would something else cause the bridge rectifier to go that I should look at too, or is it usually the culprit?

Also the curiosities. The cap at C506. The kit and everywhere I look it up, people say it should be 45uf-47uf. The markings on the side of this old one says 45MF. Which my Asteroids has as well. What's the reason for the difference or is there one?
2bc272e570019c1e9cebcf4d6c36ace4.jpg


The other thing is someone had repaired this in the past at some point or attempted to and the transistors at Q704 and Q604 should be U57. These are JE253 with their legs crossed. Is this acceptable and that's all they had at the time or should I just replace them with U57?
40d627b8b1d773e7f769193c2d6f78b4.jpg


Thanks for the help.
 
Test all transistors, and especially the diodes. There are several diodes that often blow on these, as well as the Zeners that can go as well, which are under the two large resistors on the deflection board (there are four of them, however some versions of the board don't have them).

Basically you need to test everything.

And yes, that cap can be replaced with a 47uF. (MF = microfarads = uF, in old cap lingo).
 
Test all transistors, and especially the diodes. There are several diodes that often blow on these, as well as the Zeners that can go as well, which are under the two large resistors on the deflection board (there are four of them, however some versions of the board don't have them).



Basically you need to test everything.



And yes, that cap can be replaced with a 47uF. (MF = microfarads = uF, in old cap lingo).



Okay. Cool. How about those crossed legged transistors, should I just replace them with the correct ones or are they okay like that?
 
They're fine like that as long as they're ok. They were installed that way at the factory, due to not having the proper pinout ones, as they were making these so fast they often couldn't get all of the ideal parts for them, so subs were sometimes made.
 
They're fine like that as long as they're ok. They were installed that way at the factory, due to not having the proper pinout ones, as they were making these so fast they often couldn't get all of the ideal parts for them, so subs were sometimes made.



Thanks. Good to know. They tested okay. I'll get to work on all testing all these diodes.
 
And yes, if the bridge rectifier is bad, you will need to replace it, however you'll need to check everything else on the power supply as well, as the Zeners and bottlecaps on it can also be taken out too.

FYI, I have refurbed and warrantied 801 boardsets available, if you get fed up and want to trade yours in at any point.
 
And yes, if the bridge rectifier is bad, you will need to replace it, however you'll need to check everything else on the power supply as well, as the Zeners and bottlecaps on it can also be taken out too.



FYI, I have refurbed and warrantied 801 boardsets available, if you get fed up and want to trade yours in at any point.



Good to know. I've already tested the bottle caps. They're good and those 4 Zeners you mentioned. I still need to check all the others.

I'll keep it in mind about the boards. I'll give it my best shot to fix it myself. This game came from a local space museum and it's a project for them that they want to advertise in my arcade when it's done and the first time I'll get paid to fix a game. I already got the game itself to play blind. The monitor is all I have left to do, so your help is very appreciated.
 
I replaced the bridge rectifier and checked the other diodes. The monitor has come back to life! However, every once and a while the whole screen will partially collapse like the power has been flicked off then back on. Is this problem most likely in the HV section or somewhere else, maybe even the Lunar Lander board itself?
 
Realistically it could be any of them. Hard to say without doing some measurements.

You can put a DMM on the XOUT and YOUT test points on the game board, and see if they go to zero when the screen blanks, which would tell you it's the game board.

Or post a video.
 
Realistically it could be any of them. Hard to say without doing some measurements.



You can put a DMM on the XOUT and YOUT test points on the game board, and see if they go to zero when the screen blanks, which would tell you it's the game board.



Or post a video.



Okay. I'll see if I can post a video.
 
That's an issue with your HV cage. Cap and reflow it.

Something looks like it may be arcing in the cage. Make sure (after capping and reflowing it) that no components are too close to each other, and/or that there are no other signs of shorting anywhere in the cage. Though the recapping will likely cure it, if it hasn't been done, as the caps are usually toast if they are original.

You should also get an HV probe in order to properly measure and adjust your HV, as we don't know where it is currently set. You can get a used Fluke 80k-40 on ebay for 50-80 bucks.
 
Cool. I have already recapped it when I first got it in, but I'll check them again. I just bought a HV probe last week to work on these monitors (Tenma 72-6530). I've never used it for that purpose yet just to discharge. First time for everything. A little training would be useful.
 
Who did you get the cap kit from?

Also, check to make sure the anode wire is fully seated in the hole of the tube, and make sure it's making good contact. It looks like you're getting arcing somewhere, which is killing the HV momentarily, then it builds back up again, and repeats, hence the blooming. It could theoretically also just be happening because it's too high, so you want to measure it first. See the 801 manual for what it should be.

As for the HV probe, google up some vids. I think John's Arcade has some where he uses his probe.
 
Who did you get the cap kit from?



Also, check to make sure the anode wire is fully seated in the hole of the tube, and make sure it's making good contact. It looks like you're getting arcing somewhere, which is killing the HV momentarily, then it builds back up again, and repeats, hence the blooming. It could theoretically also just be happening because it's too high, so you want to measure it first. See the 801 manual for what it should be.



As for the HV probe, google up some vids. I think John's Arcade has some where he uses his probe.



I got the kit from arcadepartsandrepair.com

I'll look into the rest shortly. Thanks.
 
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