Neotec 2515C Good B+ no image

DrewZ

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Greetings all,

I am working on a 2515C that has no image. B+ is exactly 125vdc, I played with the shutdown pot with no result. The usual suspects test good, but I've never noticed a flyback with a loose magnet before?
Can anyone confirm this shouldn't move around so easily?

Thanks
 

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Ok so my NTE 2353 HOT is reading shorted base to emitter in both directions. still curious about this flyback.
 
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This kind of HOT with built-in damper diode also has a low ohm resistor (40-50 ohm) across base and emitter. It's low enough to make the meter beep but it's not a short.

Any sign of high voltage to the tube (static electricity on the front glass, noises, greyish raster if you turn the screen/G2 pot on the flyback)?

Check for 160V on C920 on the neckboard. If the voltage is lower (about the same as the B+), the flyback is not working.

Check for 12.5V (coming from the PSU) on pin 10 of the LA7850.
 
This kind of HOT with built-in damper diode also has a low ohm resistor (40-50 ohm) across base and emitter. It's low enough to make the meter beep but it's not a short.

Any sign of high voltage to the tube (static electricity on the front glass, noises, greyish raster if you turn the screen/G2 pot on the flyback)?

Check for 160V on C920 on the neckboard. If the voltage is lower (about the same as the B+), the flyback is not working.

Check for 12.5V (coming from the PSU) on pin 10 of the LA7850.
Thanks, I didn't know that about the HOT, I wasn't getting the expected .5v like I do when going from B to C. No static or signs of life at all, I have the chassis out and the fuse holder broke off on one side when I barely touched it so a new holder and a flyback while I'm at it are on the way. The core of this FB moves up and down by almost 1/4".
 
If it's just loose and not cracked the flyback will work anyway. Worst case it will make some buzzing noise that you can fix with some epoxy or silicone (it can be seen in your pics that the old sealant came off).

B-E is as you said on the HOT of the K7400/U5000. On the K7000 and this Neotec it's different.
This is how this HOT (a good one) should read (voltage drops are for reference only, they don't have to be exactly those):
transistordiode.jpg
 
If it's just loose and not cracked the flyback will work anyway. Worst case it will make some buzzing noise that you can fix with some epoxy or silicone (it can be seen in your pics that the old sealant came off).

B-E is as you said on the HOT of the K7400/U5000. On the K7000 and this Neotec it's different.
This is how this HOT (a good one) should read (voltage drops are for reference only, they don't have to be exactly those):
View attachment 855810
Thanks I'm saving that one for future reference. Based on that my HOT is good. Looking into some bench tests with just a multimeter for the flyback now.
 
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A few readings from the flyback with a DMM. Probably not how you would test these but a few readings marked ? don't make sense to me.

10-9 0.2ohms
10-8 0.4ohms
10-3 0.1ohms ?
10-6 open
9-8 0.4ohms
9-3 0.2ohms ?
9-6 open
8-3 0.8ohms
8-6 open
8-5 0.4ohms
3-6 open ?
5-6 open ?
2-6 open ?
1-2 1.2ohms
 

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Measuring resistance across pins is pointless. The only relevant info is that the primary winding (1-2) is isolated from the secondary winding (infinite resistance across 1 or 2 and the other pins) as it should.

My suggestion is to make sure the parts in the horizontal drive path are OK, so 12V on pin 10 of IC401, T401 supplied by B+ through R424, Q401 and Q402 good and solder joints of all these parts good too. If you can't make any progress (no secondary voltages from the flyback as per my first post), send it out for repair.
 
Measuring resistance across pins is pointless. The only relevant info is that the primary winding (1-2) is isolated from the secondary winding (infinite resistance across 1 or 2 and the other pins) as it should.

My suggestion is to make sure the parts in the horizontal drive path are OK, so 12V on pin 10 of IC401, T401 supplied by B+ through R424, Q401 and Q402 good and solder joints of all these parts good too. If you can't make any progress (no secondary voltages from the flyback as per my first post), send it out for repair.
Thanks I will follow the advice from your first post as soon as I can power it up again. I read somewhere on here you could do some testing on the flyback with just a DMM so I figured I would poke and hope.

Drew
 
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