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Not exactly an apples-to-apples comparison, but I recently got a Cinematronics / 19VARP4 setup running on a Space Wars board - and noticed a similar effect. The Cinematronics display does not have a dedicated Brightness control, but I did install a 5K-Ohm potentiometer in place of R10 (as...

When you say you are rebuilding, does that mean the monitor is outside the cabinet - on a workbench, etc.? If so, it might be something in the vicinity which has a strong magnetic field associated with it - transformer (soldering iron), fan motor, etc. Have you tried moving the monitor to a...

Agreed on the need for a video clip, but one thing that can cause the jitters are oxidized / damaged terminals / bad crimps where the Focus and Screen wires exit the HV cage through the two-wire connector (P901 / J901). Gently squeeze the female terminals with a pair of needle nose pliers to...

I know you have been through this exercise multiple times already, but I have to wonder if there is a cracked trace or broken component lead hiding in plain sight. Use the Resistance setting (Ohms) on your DVOM to check the resistance of the video and sync signal path from the input header pins...

This is a gold mine - thank you for sharing!

Next, I would test C701 (verify integrity, value and polarity) followed by CR603 - which is a AW01-08 Zener diode. First, using the standard Diode function of your multi-meter, test it for forward and reverse bias. You should be able to check the Zener behavior with a fresh 9-volt battery and...

In looking at the video, it seems that both oscillators (Horizontal and Vertical) are free-running - no hint of synchronization or attempt to lock. To me, this means there is a problem in the sync signal chain. The first place to look is on the Interface Board where the Sync signal enters. I...

Online research suggests the following: F364J = 360nF (0.36uF) 400 = 400 Volt MPP = Metallized Polypropylene Film Available here: https://www.mouser.com/ProductDetail/667-ECW-F4364HL You might want to check the lead spacing. The part listed above is 15mm lead spacing, but I'm sure it can be...

Often times, stepping away from a problematic situation is beneficial as it is not uncommon to identify an issue (or error) that was hiding in plain sight the whole time. It is also worth verifying the capacitor values and correct polarity - on the odd chance that either might have initially...

Admittedly taking a bit of WAG after re-reading what we've covered up to this point, combined with a quick glance at what you have tested thus far, and the next thing I would do it check C1 and C2 (on the Interface Board) to see if they are shorted or have capacitance values that are...

https://www.ebay.com/itm/405559588406 If you aren't interested in purchasing this set, you can use the picture to build your own: Grab a coaxial test lead with BNC on one end and split out the center conductor and shield to individual clipped leads on the other end. Another option - purchase...

Based on the fact that you are getting raster, I believe it is safe to say the flyback is operating. It is producing voltage for the cathode heaters, high voltage for the anode, and the beam is scanning - so deflection is active (horizontal and vertical drive for the yoke). It still seems like...

Wow - that is very interesting / unexpected - at least to me! Thank you for taking the time to perform the test on the D402 cathode voltage. What caught me completely off guard was the fact that the voltage started dropping - and at around 31.6V is when the shutdown occurred. The rise...

The only other thought that comes to mind is a problem in the blanking circuit - namely D01 and TR706. If the video inputs are effectively being blanked 100% of the time, I believe the result would be similar to what you are observing. Otherwise, I am sorry - I am out of ideas and don't want...

As another data point, check the voltage at the cathode of Zener Diode D402 (HZ36-2). With B+ at 115V, the voltage drop across R427 is 80.8V - resulting in 34.2V to D402. Referring to a HZ36-2 data sheet, the minimum and maximum Zener voltages are 35.3V and 36.8V respectively. If the cathode...

My only additional thought at this point is to monitor the other test points A2 (base drive for Q901), A3, A4 & A5, as well as base drive signals for Q001, Q002 and Q003. Hopefully, the meter's graphing display is fast enough to catch any transients or voltage drift which might be driving...

The 160V you are measuring is the Peak output of the bridge rectifier. When 115 VAC RMS is full-wave rectified, the resulting DC voltage is 160 volts (plus or minus). As I read through from the beginning, I see where you replaced Q002 (2SC1815)? However, Q002 appears to be part of the...

Very nice meter! :) The only routes I see that B+ leaves the power supply section are at the 115V B1 Tag (highlighted in green), and between R426 and R427 where it tees off to D402 (Pin 16 of IC401) - highlighted in yellow. The objective is to isolate B+ so it has no connectivity to the...

That certainly sounds plausible - wracking my brain trying to figure out which capacitor (or selection of components) could be responsible. What if you isolate the power supply and see how it behaves with no load and nothing connected downstream of the 115 V B+ output. Lift one leg of R427 (to...

What is the voltage (VDC) at Interface Point B1 (between the Power / Deflection PCB and the Interface PCB)? I don't know what the spec is because it is not listed on the schematic, but if it is negligible, then start tracking back across R729, L703, R732 and CR706 (Diode) to see if one of them...