4900 No Picture

Scucci

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Got another chassis ready for testing today.

Hooked it up, turned it on... no smoke... so... yay that.

But I get no picture. Brightness on the chassis itself and flyback do nothing to bring up any raster... I get no brightness control what-so-ever.

I checked Fromms flowchart... and got to the magic dead end of the flowchart... Voltage checked fine... no raster... heater is glowing... ... ... the end. That's where it stops.

I got the chassis in a bulk deal because the board was cracked. I've repaired that, fixed every trace I can think of... but I still can't get anything up on the screen.

The flyback doesn't show any signs of past explosions or anything like that... seems to be pretty sound. I'm just not getting anything on the screen.

I DID notice that the neck glows blue... there's a very light blue glow. I haven't noticed that before with the regular chassis that goes with the tube, but I just haven't really paid much attention to it... The heater still glows normal "heater color".

Anywho, any more ideas on where to go with this guy?
 
Or you have much higher voltage on some pins than you should.
 
Or you have much higher voltage on some pins than you should.

I'm learning toward that. Since I saw the blue, I turned it off and haven't turned it back on. I've seen a broken neck do it's show, it's nothing like that. I looks like the glow you get when you hook a light bulb up to a neon sign transformer... soooo... yeah, not good.

I haven't put back on the old chassis yet, mainly because it's already been a crappy day and I REALLY don't need to add "fried guns" to the list of crap... so I'll check the old chassis tomorrow... it'll either be a good start to the day (it works) or it'll be a terrible start but buried under the rest of the crap I'll have to put up with tomorrow (doesn't work, then I spend all day at the arcade making change for kids that either can't hear or don't understand English).
 
Well, the tube isn't fried... yay that. Put the old chassis in and she fired right up.

I'm getting NOTHING in the neck from the other chassis now though... No neck glow (blue or otherwise). So... yeah, that sucks. Still getting the 130V though.

As soon as I figure out how to check flybacks (ohm across what pins?), I think I'll find my answer... ... which would suck considering I don't know where to get 4900 flybacks from.
 
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