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IBM 5153 monitor not working!!!

Well, I took out the transformer,
Re-wrapped the entire thing,
and Now the power LED will turn on
and I can hear the hissing noise that
a monitor makes.
The filament does not light up.
I checked voltages at Q401 and C was 36.6 instead of 53.8
and B was .3 which is right.

Also the power supply now measures 119 volts.

I think I may have just put T401 back together poorly.
Could that affect the filament turning on?
 
Progress !! Turn the lights off and look at the filament to see if it's lit. You might not see it in room light. Did you hear the "crunch" of the high voltage when you turn it on? Also when you turn it off you should hear a slight "crackle"
as the HV decays. Run the set maybe 30 seconds then turn off and feel the temperature of the horizontal output transistor. Then increase to one or two minutes. Insufficient drive from your homebrew transformer
can cause the HOT to run hot. It should be warm but not too hot to keep your finger on it.

PS - also watch the face of the tube in the dark as you power on/off. See if you see a flash of the raster.

Larry G
 
There may be DC voltage on the HOT after powered off but usually it discharges fast. I don't think it will bite you.

Larry G
 
Check the voltage on the B and E of Q403 (the two leads). Should be about 1 volt if you are getting drive. Remember DO NOT measure the metal can (C) of that transistor, it will fry your meter !!!

Of course, only put your finger on the HOT when powered off. It is deadly when powered on !!!

Larry G
 
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I am not familiar with this "crunch" of high voltage, but I do hear the expected continuous buzz
of whatever makes that noise. I do not hear the HV decay. By the way, What is the HV?
I know what noise you're talking about but don't know what it is.
After a few minutes of running, The HOT feels warm but not too hot at all.
I have one concern though: the transformer may have the wrong polarity.
I forgot to remember which pin goes on which side of T401 :( oops!

Could I measure a certain pin on the crt board to see if the filament is getting power and the tube is broken,
or if it isn't getting power at all?

Sorry I am not too educated on this type of stuff.
Monitors and crt's are unexplored territories to me.

EDIT:
So I measured both pins of HOT and they are both 0.25v.
They are connected directly to the pins on T401.
They should be 0.94v and 1.11v
Does this mean T401 is not working correctly?

Thanks!
 
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HV stands for High Voltage. There is about 20,000 volts to the red rubber cap on the side of the tube. The buzz you hear is probably what's called vertical drive and not the horizontal drive.
Vertical drive is about 60Hz. Is the power LED on the front lit? It is powered by the same drive that lights your filament. If your horizontal drive is working, you wlll get 12V across C428 and 5V on C212.
Check those voltages.

Larry G
 
Is there any voltage on C428? I assume not. Yes, .25V on the HOT means T401 is not working correctly. It takes at least .6V for the HOT to turn on at all.
 
As Paul said, the HOT Q403 could also be bad. If you remove T401 again, measure resistance between the two leads of Q403 to see if there is a low ohms short, like 200 ohms or less.
You can unsolder a lead to make that measurement as well.

PS - bedtime for me

Larry G
 
So I measured the resistance of the leads of HOT after desoldering the wire off of one of the leads.
It measured 50 ohms. This means that I have a bad HOT right?

That would explain why .25v was on both leads of Q403.

Should I replace this and try it again?

Also, I can't believe I forgot to add that the power LED did turn on!
 
Just to clarify, you unsoldered a lead of Q403? Then 50 ohms across the two leads?
Yes, then replace Q403 but make sure T401 is hooked up correctly before powering on.
That would also explain why the C of Q401 was 36.6 instead of 53.8 since it's driving a short.
If you want, measure Q401 C while Q403 lead unsoldered to see if it came back up to 54 volts.
That might also tell you if T401 wired correctly.

Larry G
 
He seems like a young guy so his heart can take it. I got zapped many times in the TV repair business and am still talking to you ...

On the other hand, microwave oven power supplies do kill. I had a coworker killed servicing one years ago.
 
CRT's are high voltage, but not high current. It's the current that kills..

Just keep one hand in pocket, and you should be fine.
 
Well, I debate that, and here's my reasoning. The human body is a constant resistant, and yes, while you need a high voltage to get something through your body, you need 100mA to stop a heart. If it was a high voltage with little current, it'll shock you, but not stop you (permanently).

But at the same time, you can't have high current without high voltage, but a car battery can certainly do some damage, and it's not high voltage, just high current. I've heard a story about a navy officer who died from a 9v battery, however it involved open cut wounds. As to if it's true I never checked.

But it seems to stand without reason, that so far in my observations, it certainly is the current that kills, weather the higher amperage requires higher voltage, or something with lower voltage, but enough current.
 
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