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Well I think I found the problem. See if you can spot it. ;) It's a bit embarrassing how many steps I went through before getting there. Clock was present, 5V was present, no interrupt lines held, toggling reset manually produced no result. With or without the ROM, the address lines were...

Does that mean that booting without UB11 doesn't work then? I removed it in case it was holding RESET/ low, and verified that the line is high. Do I then need to bring it low and release it for the CPU to start? I do have a spare 68030 somewhere. If I can find it that's an easy test.

I've used this with a 110V Plus with fine results: http://www.maplin.co.uk/p/240v-to-110v-300w-voltage-converter-vr05f

Good thoughts. I tried reseating the 030 and the ROM SIMM, with no change. Address and data lines from the CPU to the ROM SIMM socket all test good. I don't have the scope here at the moment so I will have to test the ROM CS/ line later. Weirdly, I think the reset switch has failed but in the...

Question for the experienced debuggers here: on the SE/30, what are the first things the 68030 does when powered up, and what are the best signals to test to work out early startup problems? A while back I bought an SE/30 logic board (socketed) which had been recapped but was still...

True, almost all of the voltages except the video and the filament heaters come from the flyback secondaries. Two of them have some pretty significant capacitors (big electrolytics plus .01uF ceramics) but the voltages for focus and cut-off only get .01uF capacitors. I didn't notice a big...

More like for safety reasons! The extra charge at 13kV is risky enough; finding a way to wire it up under the anode cap is doubly challenging. Looking at the screen photo again, I do wonder whether something else is going on besides just fluctuating anode voltage. It seems like an awfully steep...

After a long break I finally got another chance to look at this. Since it's clear that some sort of phase-locking will be needed, and simple ratios of the video frequency won't always line up with the original 22.25kHz horizontal scan rate, I decided to test the effect of scan frequency on the...

Well that ended up going for not-so-cheap. Very curious what card that is. If someone here won it I hope you will post pictures!

Just bid on this. If I get it I'll post pictures of the card. And I might have to get rid of another Mac to make space! 

Interesting and rather unexpected result. The lines off the right side suggest that the timing of the HSYNC pulse, rather than the length of the retrace period, is the problem. It looks like retrace is starting too late so it isn't finished by the time the next video line starts. I might start...

OK then, if your scope probe is rated to 200V or more (probably true if it is a 10:1 probe) then you can measure the voltage on C12.  Careful though as a couple points on the analog board sit around 800V -- take the usual high-voltage precautions. You might even wire up the probe to C12 with the...

It's probably the flyback then (which is an integral part of the horizontal circuit). If you have two machines, you could try swapping flybacks before finding a new one.  Do you have access to a scope? There are a few signals which could tell you what's going on. Otherwise, another idea is to...

The problem is definitely foldover, and the reason is that, for whatever reason, the horizontal retrace is happening too slowly. The retrace speed is determined by the inductance of the yoke, capacitor C12, and the inductance/capacitance of the flyback transformer. The yoke is probably fine...

Board flexing is a good thought. A good way to test that would be just to push down gently on the board without the card inserted and see if the problem reproduces itself. uniserver is right that a broken trace is more likely than a dead UE8 (which does look to be new).  It is highly likely...

Whatever you did with the images worked that time. Maybe repost the screenshot the same way.   The card looks pretty normal. Does it work? i.e. does the system see it, and can you connect to a network?

I think it's pretty sensitive to the right HV level. I guess you could adjust the focus and brightness, but I also noticed a pincushion effect when the HV was reduced. Ultimately the HV is a byproduct of the horizontal deflection. There's not really any effective way to get it without the...

It looks like that image didn't post correctly (same problem as the first post). Can you repost the link to the larger version? A high-res image of the MacCon card would be interesting too. And sorry to repeat myself, but does the ethernet card work? If it does that narrows down the space of...

UE8 is a surface-mount chip which is located roughly between the large capacitor C2 and the crystal Y2. It's a common victim of cap goo, which can rot out the connections inside the chip. Since the video problem only affects a single bit where the VRAM is loaded a byte at a time, it suggests...

If the logic board hasn't been recapped, this is probably a straightforward caps issue. Though the ethernet card may be the trigger, maybe loading down a failing trace on the logic board, I wouldn't be surprised if the real fault is on the logic board itself. Vertical stripes are often UE8...