Neotec 36" 3501 Advice pls..

supadave1

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Neotec 36" 3501 Advice pls.. (pic now included)

Neotec 36" 3501 Chassis RCA Tube

A showcase cab I'm looking at has one of these in it. However, the picture is dim. I turned the brightness up on both the control and flyback. No go.. Is this more than likely a Tube problem or is it chassis related? The tube is an RCA btw. I do not want to have any part of this if the majority believe it to be a tube issue. A chassis issue I can deal with.. I'm just looking for some feedback from some more experianced monitor techs.. Also what about the idea of a Tube swap from a TV.. I have access to a 36" TV RCA too..???

Thanks
 

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I won't go so far as to say it isn't a tube problem, only a tube tester will tell you for sure, BUT, I have been seeing many Neotec's with dried out caps in the SMPS output causing low voltage to the heater circuit. The heater voltage is derived from the power supply instead of the flyback on these. Bad caps in the power supply can cause the heater voltage to drop and create a dim picture.


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Check your heater voltage at the neck board to see if you have around 6volts. if it is around 4volts or less then you have a chassis problem(caps in power supply section). If you have the voltage it is more then likely it is your tube. You could read the resistance across the heater pins on the tube(game unplugged and tube discharged) and check for about 2 to 5 ohms. This will tell if the heater inside the tube is good. If everything is good then rejuve.
 
Awesome, thanks for the tips.

Check your heater voltage at the neck board to see if you have around 6volts. if it is around 4volts or less then you have a chassis problem(caps in power supply section). If you have the voltage it is more then likely it is your tube. You could read the resistance across the heater pins on the tube(game unplugged and tube discharged) and check for about 2 to 5 ohms. This will tell if the heater inside the tube is good. If everything is good then rejuve.
 
Here is a pic of the chassis.. Maybe you guys can see something I don't that would contribute to a dim screen issue. I do see some dark spots..

Thanks everyone for the help so far in understanding this. I don't want to make this purchase and be stuck with an expensive dead tube.

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Nothing out of the ordinary jumps out at me in that picture. The darkened areas on the board are normal and typical. The components in those areas (power resistors) do give off some pretty good heat and will discolor the board over time.

In your picture, the caps in the upper left hand corner of the board are the most suspect ones. Those are the filter caps for the power supply. They take a beating in normal use. While the heater circuit caps are the most common failure, any of those caps can cause troubles. Judging from your picture I'd say most, if not all, of those caps are original. The monitor is probably due and I'd do a full cap kit on it.

You can still go thru and test heater voltage and so forth, that will give you a fair idea about the condition of the chassis and if the heater circuit is contributing factor in the dim image, but the only way to know %100 about the condition of the tube and the gun emissions is to either recap that chassis and see how it looks or test the tube with a rejuv/tester.

I can tell you that, in general, the RCA tubes Neotec usually used held up much better than the POS Zenith tubes that Wells Gardner was using and I don't see tube emission issues on the Neotec's very often. But that's just been my experience.


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