WG K4606 heater voltage 1.5VAC

Minnesota 13

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No neck glow but HV. Measured the heater voltage looking for 6.3 but it is at 1.5VAC. So do I need a complete replacement flyback?
 
You can't accurately measure heater voltage. The best you can do is to compare a heater voltage reading from a known working monitor.

The reason, as CharlieG stated is it is a 15khz signal, and multimeters measure a normal AC signal of 50hz or 60hz.

What is the monitor doing? or what is the problem with it?
 
Using regular voltmeter measuring heater voltage. Sold my scope. There is no tube neck glow. B+ and HV OK. Otherwise the the CRT is dead/dark. With the flyback heater input connector removed from the neck board the heater resistance is 3.5 ohms - neck board connected to the tube. Includes resistor R422 on the neckboard. This is measured at R422 resistor input and chassis ground. I would surmise if the filiment was open I wouldn't see any resisiance.
 
No neck glow but HV. Measured the heater voltage looking for 6.3 but it is at 1.5VAC. So do I need a complete replacement flyback?
you measured at R422, but is it 1 ohm? also make sure all the solder connections are good at the plug header pins and I would resolder the neck socket for added measure.

K4600 heater.png
 
Do you have a rejuvenator or a known-working chassis with which to test the tube?
 
What meter are you using to measure the heater voltage? A lot of DMMs can't accurately read the 15khz AC voltage on the heater circuit.

That's right. DMMs are digital sampling devices. You need an analog meter to measure that. Something like this beauty:

EDIT: I'm talking about a Simpson 260. With a mechanical movement and a needle. I'm having network issues and can't upload photos at the moment.

EDIT #2: Simpson 260 picture!
(Hallelujah! Working network! )

1754921232245.png
 
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That's right. DMMs are digital sampling devices. You need an analog meter to measure that. Something like this beauty:

EDIT: I'm talking about a Simpson 260. With a mechanical movement and a needle. I'm having network issues and can't upload photos at the moment.

In my experience, cheap $10-$20 analog meters won't cut the mustard here. I personally was never able to get my Rigol digital scope to do it either. I've never used the Simpson, but the only meter I've seen accurately measure heater voltage is a Fluke 87 that I borrowed from @security0001.
 
In my experience, cheap $10-$20 analog meters won't cut the mustard here. I personally was never able to get my Rigol digital scope to do it either. I've never used the Simpson, but the only meter I've seen accurately measure heater voltage is a Fluke 87 that I borrowed from @security0001.

Yeah, that's a lot of meter. I love my Fluke 87-V.

$10-15 is in the toy category for an analog VOM. But it's no different than a DMM....somewhere around $30-50 is where you start seeing "acceptable" durability and performance for meters. It goes up from there depending on what you need to measure and why.

Just like every tool, you have to understand what it measures and how. And you have to understand how it interacts with the device you're trying to measure.
A quality meter will have 20 kR/V input whereas the cheap meters probably have tiny input resistances of 1 kR/V or even less. And if they use cheap resistors and poor layout the AC repsonse will be erratic. The inertia of the mechanical movement will act as a low pass filter to average out fast AC voltage readings. This is not true-RMS and each meter does it a little differently.

To be honest, I've never tried measuring anything above maybe 1-5 kHz with an analog meter. 15 kHz would be interesting to see. I don't have a Simpson or a Triplett meter, but I have a pretty good Radio Shack one. Next time I'm working on a monitor I'll try to remember to test this.
 
My digital meter is true rms. But how about trying a 6V lamp to test it or will it draw to much current vs the CRT heater? The HV is good as I hear the crackle at startup and when grounding the HV at the tube a nice pop. I failed to mention that I replaced all of the electrolytic caps and replaced the black level pot. The CRT didn''t work before the cap update. Would measuring heater current draw be indicative of anything of value.
 
That's not the point. My Fluke 117 is also "true RMS" and it cannot accurately measure a 15kHz AC voltage.
That's right. It's about the sample rate. For a 15.7 kHz signal, you need a meter capable of at least 31.4 k-samples/second.
After you correctly sample the voltage waveform then you have to do [some math] to obtain an equivalent DC "heating" voltage. That's where the RMS computation comes in.
 
I was answering the question to what kind of meter I am using not debating the functionality of a digital meter in measuring high frequency voltage. I thought about measuring the current draw to determine the voltage. The tube heater resistance is spec at 2.5 ohms. The heater winding on the flyback is not open.

As suggested the pins to the tube socket were re-soldered and the tube screen has light. Adjusting the screen pot the tube starts at dark then a full yellow screen to white to the raster bars. I will have to sort out my connections to the the monitor. Thanks for all of the comments.
 
I was answering the question to what kind of meter I am using not debating the functionality of a digital meter in measuring high frequency voltage. I thought about measuring the current draw to determine the voltage. The tube heater resistance is spec at 2.5 ohms. The heater winding on the flyback is not open.

As suggested the pins to the tube socket were re-soldered and the tube screen has light. Adjusting the screen pot the tube starts at dark then a full yellow screen to white to the raster bars. I will have to sort out my connections to the the monitor. Thanks for all of the comments.
if you see anything on the screen then the heater is at least doing something. lol

it's also conventional wisdom you can't see neck glow on a lot of tubes. it's why I don't use it as the metric of whether a monitor works or not. you can touch the front of the screen to see if there's static or in my case, you can't hear the 15 KHz. except where I work. because they decided a jukebox belonged in a video game arcade playing the same 10 songs on repeat because no one knows how to choose their own songs.
 
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