Space Invaders-new tube. How to check B+ voltage?

philsfan64

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I put a NOS picture tube in my Space Invaders upright. Picture looks fantastic. It looks like a brand new game. Do I need to check the B+ voltage? I didn't touch it. I'm not sure how to check it. I just want to make sure I'm not overdriving anything. The chassis was completely recapped a few years ago by Chad at Arcadecup. The chassis is a 19V1001 and the tube is a Phillips M47EAA7WD. I have a schematic but it's difficult to read. The instructions mention a signal generator. I don't have one. I would appreciate any tips on how to do this. Thank you.
 
If you only replaced the picture tube and nothing else then odds are everything is fine, particularly if you had someone experienced rebuild the chassis.

If you want to check it yourself to be on the safe side it is pretty simple. You only need a multimeter and ideally an alligator clip so you don't accidentally short across two pins using just the multimeter leads (unless you have rock steady hands). Page 7 of the 19V1001 manual contains easy to follow instructions under "Regulator Adjustment". You are looking for 75 V at the indicated test point.

I would strongly recommend using one of the test points along the edge of the PCB rather than trying to clip directly onto the emitter of the regulator as the manual suggests. To determine which test point they are referring to, you need to first find the emitter of the regulator. The middle diagram on page 3 shows this clearly. The regulator is Q101 and the emitter is indicated by the outward facing arrow inside the circle. Follow that trace up and to the right and you'll see it labeled 75 V. The "2" with the downward arrow indicates a test point position on the board. Page 10 shows the image of the main PCB with test point "2" across the bottom edge. The PCB has these numbers silkscreened on them, so it should be easy to find. Clip on the metal stake at "2" and the other end goes to your red multimeter lead. Place the black multimeter lead somewhere on the metal frame or any convenient ground point. If you are at 75 V or really close to it all is good. If you need to adjust, use the large potentiometer R212 in the corner of the PCB. Move it slowly and double check until you get 75 V.
 
That is extremely helpful. Thank you very much. I will check it this weekend.
 
One more question. Should brightness and contrast just be at their normal position for this voltage reading? It doesn't say anything about that in the manual so I'm guessing it has no effect but I just want to be sure.
 
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I don't think brightness or contrast will impact the measurement. Just keep them where you think the picture looks best. The manual says to adjust the horizontal and vertical oscillator until the picture is stable (yours already is) since the speed at which they run could probably load the power supply slightly lower or higher. Your 'test signal' should be the video game running as you won't be using this to watch TV or anything like that.
 
I don't think brightness or contrast will impact the measurement. Just keep them where you think the picture looks best. The manual says to adjust the horizontal and vertical oscillator until the picture is stable (yours already is) since the speed at which they run could probably load the power supply slightly lower or higher. Your 'test signal' should be the video game running as you won't be using this to watch TV or anything like that.
Very good. Thanks again. I'll report back.
 
Just about perfect. I didn't touch a thing. Thanks again for your help.
 

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Excellent! Just curious where you found the NOS tube? I bought a few from a supplier on eBay many years back but they are out of stock. I have a couple more Bronze Age games that could use a refresh.
 
Excellent! Just curious where you found the NOS tube? I bought a few from a supplier on eBay many years back but they are out of stock. I have a couple more Bronze Age games that could use a refresh.
The seller is crtsolutions. He has 100% feedback.
 
Excellent! Just curious where you found the NOS tube? I bought a few from a supplier on eBay many years back but they are out of stock. I have a couple more Bronze Age games that could use a refresh.

Just a visit from the bumpasaurus. My son has a stash of monitors that have that tube in them. Burn free.



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