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It can be a huge problem. One check I like to do is to probe various spots on the board with an ohm meter. Any reading at all means it's not clean.

There's no need to discharge the CRT unless you need to disconnect the HV cable from the CRT bell. Most monitors do self discharge due to the resistor network that creates the focus voltage, but it's always wise to assume it's charged before touching the HV connection. If it's not powering on...

Based on that, you can rule out any kind of major fault like a shorted power transistor, or bad power supply driver IC. Depending on how much capacitor leakage there was, there could be some subtle damage from that. Maybe an open resistor, or electrical leakage on the board if it wasn't...

I think people are often too critical of the 5154. I've worked on about 10 of them in recent years, and all but one were still in excellent condition as far as heat damage went. Even the worst one just needed a bunch of new caps, which isn't unusual on a heavily used monitor. I just repaired...

When I said to measure the voltages on the cathodes, G1, and G2, I just mean to use a volt meter. At this point, we're just trying to figure out why the screen isn't lighting up. It's wise to check voltages with a meter before connecting your oscilloscope probe to a CRT because there are high...

It looks like it should be easy to solder some short wires to some of the input pins to compare signals. If the red, green, and blue inputs look similar, then it almost has to be the DAC itself.

I would try to verify what's going into the DAC first. Display a screen full of red, or green only text, and compare it to the signals for blue only text. If there's nothing going into the DAC on the red, and green, then it's probably not the problem. A datasheet for the DAC chip would be...

The magnets on the CRT are usually to correct color purity errors in the corners. The pictures you show look fine to me. These things were never perfect, even when new. It's one of the things that tended to be better (but still not perfect) on high priced monitors, compared to cheaper...

I'm in Austin, and I do repair these for people. If you're ever in the area, I can definitely help you. I've had people ship them to me, but it's a lot of extra work to pack them properly. At least the 5154 cabinets seem to be aging better than the 5153, which is almost always brittle. As...

It's possible that the monitor intentionally blanks the picture when it doesn't have valid sync signals.

There's a good chance the problem is related to all that corrosion. The adjustment pots look like they could be damaged, or dirty. The sub contrast control could cause no video if it was open circuit. Since you have high voltage, I would try turning up the screen/g2 control (usually on the...

I've been working on electronics for many years, and I have yet to see a switching power supply transformer fail. I'm not saying it can't happen, it's just incredibly rare. Since the fuse is now blowing instantly, something must be shorted. You need to check all the power transistors, and...

How did it work before the recap? Is this a new problem, or something you were hoping to fix with new capacitors? It's hard to see a lot from your shaky vertical video, but it looks like there's a lot of over scan (DOS text is cutoff on the left). This monitor should under scan about 0.5-1"...

Now that I think about it, there was a known issue with some 8513s having defective flybacks which caused poor focus. I think this is the part you need, but double check: https://www.tedss.com/2023000668

Since there was a short, I would look for a fusible resistor that could have gone open. You can start by confirming that the vertical IC is getting power. With no schematic, you can use the datasheet for the IC to find out which pin is for Vcc.

I'm not quick to condemn a flyback. Flybacks are pretty reliable, but anything with high voltages can fail. It's not that unusual for problems to develop shortly after resurrecting something that hasn't been used for many years. Failure modes I have seen are shorted turns, arcing, or failure...

The resistance of your test probes can easily add 0.5 ohms. What do you read when you short the probes together? Subtract that from the reading for low value resistors like this. A focus problem is very likely to be caused by a bad flyback transformer. I think the 8513 was known for flyback...

The width of the raster in your picture looks completely normal to me. Monitors from that era underscanned a lot more than later CRTs. "Edge to edge" scanning didn't become a thing until CRTs had square corners.

Before you remove the back plate you should first remove all of the key caps (except the space bar). This takes the pressure off the springs so they don't fly everywhere. It's also much easier to reassemble it with the key caps removed (except for the space bar which can't be easily installed...

Did you clean the board around the leaking capacitors?