Asteroids G05-801 troubleshoot

Kalamath

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Here's where I am. I have an older Asteroids cab that is:
-New to me
-Plays blind, full sound, and graphics display on oscilloscope.
-I've pulled and checked the G05 boards & installed Bob's cap & transistor kit.
-C100/101 tested out good on the ESR meter.
-New Big Blue
-No neck glow
-No spotkiller
-Chatter from the tube

Voltages on the AR board are good. 5 is spot on, 10.3 is 11. something.

Voltages on the fuse block are:
1 = 5.73 VAC
2 /3 = 18.70 VAC
4/5 = 10.33 VAC

Voltages at the regulator board on P101:
1/2 = 26.73 VDC
3/4 = GND
5 = -26.35 VDC
6 = ----------
7/8 = 7.09 VAC

Before replacing caps & transistors, I had some on screen display, but it was totally garbled, vectors flying all over.

I'm looking for some guidance on where to go, what to test from here.
 
There's your problem. It'll never produce a picture without a working heater.

Find the fault in the 6.3VAC.

Remove connector P5 from the power brick.
Set your meter for 20vac
Red lead to pin 6
Black lead to pin 7
6.3vac is expected

If 6.3vac is present, plug P5 back into power brick.

Pull deflection board out of monitor and test F100 & F101 to see if either of them is open.
 
Ok, after a unavoidable delay last night, I'm back at this today. Thanks for the feedback guys. Also, if a mod reads this I guess it should be moved to Monitors.

Testing where Dok suggested I get 37.5v on pins 6/7 and 7.1v on 8/9. This is a bit high (it calls for 28VAC+/- 15% on 6/7), but where I'd expect from the schematics.

I also measured 7.1v at P100 on the regulator board. Both fuses are good.

If the 7.1v is too high, how do I get that down? The voltage selection plug on the power supply is the yellow one, marked for 120v. so that should be correct. Aside from the big blue (new black one from Bob Roberts), I see nothing else I can mess with here. There's no voltage regulator like on later power supply assemblies.

ps. Remember this is a G05-801 and an older Asteroids setup.
 
7.1v on 8/9. This is a bit high (it calls for 28VAC+/- 15% on 6/7), but where I'd expect from the schematics.

I also measured 7.1v at P100 on the regulator board.

If the 7.1v is too high, how do I get that down? The voltage selection plug on the power supply is the yellow one, marked for 120v. so that should be correct. Aside from the big blue (new black one from Bob Roberts), I see nothing else I can mess with here. There's no voltage regulator like on later power supply assemblies.

No, it can't be adjusted.

Are you sure there's no neck glow? Check in a dark room.
 
Reading through the G05 manual and Asteroids schematics trying to understand how this all goes together.

Since my voltages are in range, and getting TO the monitor, my problem lies somewhere on one or more of the three monitor boards. I had neck glow prior to recapping. Since I recapped, I will pull the boards and re-verify the caps again. I was careful though, and all went well on first power up, so I'm hopeful my work so far is not the issue.

It seems the heater voltage is strictly contained on the regulator board, so I should just focus on this component until I find the issue and get neck glow. Is this a safe assumption?


Also assuming my PCB is fine since it plays blind and gives me this:
12%2B-%2B1
 
Yeah, it seems clear that the game board is fine. Problem is in the monitor boards or connections.

The 6.3VAC "circuit" is pretty simple; it does into the board, one leg goes thru a resistor, then back out of the board. Did you re-solder the headers joints when you re-capped the monitor?? They're often cracked.
 
It's definitely not the 6.3v circuit. I've traced that all the way to the neck. I'm not sure if this signifies anything, but voltage is getting to the CRT. I get a solid ZAP when discharging the anode before pulling the boards.

I checked all the header joints and saw no signs of cold solder but I'm going to reflow everything right now and then re-test.

Of note: the boards looked mostly original when I recapped them. They only signs of work that I can see is Q504 on the deflection board was replaced at some point, with re-work on the joints there and R516 (brightness pot).
 
You really should be using a HV probe or a resistor to gnd when discharging the second anode on any vector montor with the inline diode on the HV wire. The screwdriver method can wreck the HV diode...and those ain't gettin' any easier to find.
 
I'm not sure if this signifies anything, but voltage is getting to the CRT. I get a solid ZAP when discharging the anode before pulling the boards.

There are numerous voltages required by the CRT. Getting a "zap" when you discharge it means that the high voltage generation circuit is working, which is necessary, but not sufficient, to make it work. And it has nothing to do with the heater (aka filament) voltage... on a B&W vector monitor.

It's definitely not the 6.3v circuit. I've traced that all the way to the neck.

If you're CERTAIN that 6.3VAC is making it to the neck. AND you are CERTAIN that you DO NOT have ANY "neck glow", that's bad news. It sounds like the heater filiment may be burned out. On the CRT neck, with it unplugged, check the resistance between the two filament pins (the ones that the 6.3VAC connect to). If you get infinite resistance (open circuit, out of range) then the CRT is toast. If you get a reading (not sure what normal is; maybe less than a thousand ohms?) then things just don't add up...
 
Pulled all the boards, verified my caps (all good) cleaned up each and every pin joint and re-flowed them all with just a touch of new solder. Cleaned the pins again, everything looked good, so I reassembled & tested and am rewarded by a fully working monitor.

Geometry is a little off, but otherwise it's solid. So perhaps it was a bad solder joint somewhere. VISUALLY, they looked fine. No classic cold solder joints anywhere (I checked them all under a magnifying glass even!), but still...that's what it had to be.

After this, I'm really encouraged to buy a first class desolder station and make re-soldering pinouts a SOP when working old boards with fresh new solder.
 
Pulled all the boards, verified my caps (all good) cleaned up each and every pin joint and re-flowed them all with just a touch of new solder. Cleaned the pins again, everything looked good, so I reassembled & tested and am rewarded by a fully working monitor.

Geometry is a little off, but otherwise it's solid. So perhaps it was a bad solder joint somewhere. VISUALLY, they looked fine. No classic cold solder joints anywhere (I checked them all under a magnifying glass even!), but still...that's what it had to be.

Not sure if the 801 has these, but there are four pots on the 802 for controlling the horizontal & vertical linearity. They're all labeled "linearity," but really there's one size & one linearity for the X & Y axes.
 
Some folks missed this but....it's fixed. Works great, in fact. =) Came to life after I reflowed all the headers, even though they looked fine.
 
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