Monitor wavy image

trickman

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I have an Arkanoid: Revenge of DOH standup conversion that I found out used to be a Centipede cab. The monitor picture looks decent, except I have this wave that goes across the screen. Looked at the monitor and it says it's an Electrohome 19" GO7CBO. I tried to adjust it, but it's still doing the same thing. Please help. I'm a monitor noob, so please be gentle. Thanks!
 
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Check your monitor's B+ voltage. It should be 120v DC. To do this, connect the black lead of your meter to the frame of the monitor, and the red lead to the far side of the white ceramic resistor on the left side of the chassis (end of resistor farthest from the flyback, should have white wire). If it's too low/high, adjust it with the B+ adjust pot, located in front of the vertical hold pot, facing straight up on the board.

Chances are, you won't be able to get it stable. That "wave" in the picture usually means that the B+ voltage is getting some AC hum in it, because the main filter cap is weak. It's the big (usually grey) one on the chassis. It's 600uf, but replace it with a 680uf (modern common value).

-Ian
 
Check your monitor's B+ voltage. It should be 120v DC. To do this, connect the black lead of your meter to the frame of the monitor, and the red lead to the far side of the white ceramic resistor on the left side of the chassis (end of resistor farthest from the flyback, should have white wire). If it's too low/high, adjust it with the B+ adjust pot, located in front of the vertical hold pot, facing straight up on the board.

Chances are, you won't be able to get it stable. That "wave" in the picture usually means that the B+ voltage is getting some AC hum in it, because the main filter cap is weak. It's the big (usually grey) one on the chassis. It's 600uf, but replace it with a 680uf (modern common value).

-Ian

Guess I have to invest in a meter! (real noob here). Thanks for the advice! BTW, would the main filter cap replacement most likely fix the problem if the B+ pot adjustment doesn't?
 
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Well, I tried to adjust the B+ pot with no luck. The B+ adjustment pot seemed to be missing the part where it turns, as it looked sparse and not like the other adjustment pots; hence I couldn't really do anything with it. Could a broken adjustment pot be the reason it's waving like it is?
 
What do you mean, missing the part where it turns? That's like the simplest, most basic pot ever. There should just be a slot in the top metal piece, and you adjust it with a screwdriver. If the metal piece is missing, then the pot will be completely open. It's only two bits of metal crimped around a carbon disc.

What's your B+ voltage read?

-Ian
 
What do you mean, missing the part where it turns? That's like the simplest, most basic pot ever. There should just be a slot in the top metal piece, and you adjust it with a screwdriver. If the metal piece is missing, then the pot will be completely open. It's only two bits of metal crimped around a carbon disc.

What's your B+ voltage read?

-Ian

It looks like the metal piece is missing and it's completely open.

Planning to pick a meter up today. Are either of these competent multitesters? Does it matter which one I get?

http://www.radioshack.com/product/index.jsp?productId=2103170
http://www.radioshack.com/product/index.jsp?productId=2999093
 
Honestly, they both look like cheap junk. You don't have to spend a lot of money to get a perfectly serviceable meter, but those particular ones probably aren't what you want. Cheap analog meters tend to be very unreliable and inaccurate. Also, if you've never owned/used a multimeter before, reading an analog meter can be confusing. Spring for a digital meter, a perfectly usable one shouldn't be more than $30 at Radio Shack.

It's not that I don't like analog meters - I do, and they can be very accurate... but the modern cheap ones tend to drift badly, are hard to keep zeroed, and aren't anywhere as accurate as a cheap digital meter.

-Ian
 
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