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There is something wrong with the smaller die. The smaller die part has a higher transition frequency than specified on the original data sheet, but that can cause HF instability for some circuits designed for the original part. So it is a bad idea to economize on the silicon and change the...

I got some excellent genuine Mitsubishi 2732 ROMs now and I was able to complete the video boards. I only had enough IC's and other parts to make 3 boards/Adapters in total. There are a lot of interesting parts, including the right angled connector that mates with the AIM-65, the only ones I...

That shipping is outrageous. Maybe there is a supplier of them nearer to you ? Some History here: The original Bob Parker ESR meter was sold in Australia as a kit, going back over two decades. These kits are still (amazingly) available, they are wonderful, you can get them from Altronics mail...

Unfortunately there is a lot of nonsense on the internet about doing things like re-capping VDU's and other things like discharging the CRT, when it is unnecessary and can lead to a lot of trouble. On the capacitor issue, generally most radial electros are pretty long lasting unless near heat...

If the diode polarities are as you have drawn it, one 1N4148 diode is conducting in the forward direction, while the other is going into zener breakdown, acting like a 90 to 100V zener, so only the peak of flyback getting through to the blanking transistor. It could be though that the H blanking...

.... the correct damper CR504 is under the transformer, so two parts have the same designator and the one labelled damper isn't it.. You would just use a DMM (digital multi-meter) set on volts range to check voltages, generally most meters are auto-ranging and it will show you the voltages...

I wouldn't go replacing anything until you have done more tests and formulated a diagnosis. As you can see from the schematic, the +80V supply powers the load for the video output amplifier which drives the CRT's cathode, and also powers the grid, via a 100 k resistor. The circuit, to reduce...

I think with the original packing being so good, you could check that through as over-sized airline luggage, and it would probably be ok. No worse than any other shipping method, probably better as there are less steps involved and "Every stage in the shipping is equivalent to throwing the item...

(you obviously would have checked that C622 wasn't defective and the other parts around it were ok?) That ESR meter looks fine, though I have never used that model. My favorite ESR meter is the one designed by Bob Parker which uses a low amplitude pulse method, in its current current form it...

Normally there is no ringing of any significance on the terminals of the flyback transformer primary, except for the flyback pulse itself, which represents a half cycle of un-damped oscillation where the flyback is operating in a resonant (un-damped mode) and this allows the polarity of the...

Looking at the original post, I think CHAT GPT confabulated the entire story (joking of course). After working with it for a while, I got it to confabulate data, when it had no definite answer, so it was already half way there. I also got CHAT GPT to admit that if there were 100 people in one...

Like I said before, when somebody said they didn't want styrofoam and boxes, you can see how the packaging was specifically designed to protect the unit in transit. You would never get anything like this, not even close, when an ebay seller wrapped up a used computer for shipping.

The next move would be to start an exhaustive search for the schematic. If it cannot be found, the only thing one can do is to sit down initially with a pencil & paper and start to draw the schematic out. Once that is done, then a neat copy of it helps with a drawing program. You would not...

If the flyback transformer overheated, it implies something is overloading it, or the drive to the horizontal output transistor is incorrect or the transistor is shorted, but those two latter things are not the case because you would not have had the raster scan you had before you changed it...

I really like the idea of exact clone S-100 boards and S-100 computers. Because you can mix in original boards when you can find them or use clone boards. One advantage I think of exact clones of the boards is that all the manufacturer data, software/firmware routines, schematics applies to the...

It is a tad suspicious that D605 measures exactly the same in both directions, since the voltage drop is low and likely the measurement represents the external components. For that one, lift or disconnect one leg of it and repeat the diode mode test.

If it measures the same in both directions, probably that resistance is normal for that part. If the meter currents were a result of the external circuit to it, often the measurement is affected by the polarity of the test.

The DC resistance of the coil L601 might be normal for that coil, or it could possibly be open. Normally the DCR would be lower and a DMM show continuity, unless it is a very small part with a lot of fine wire. You are possibly reading an in circuit value that is giving the 27.5 Ohms. One quick...

That link is helpful and the OP should have provided it, plus there is more: If the OP wants an A on an assignment and sends it in for marking, imagine the Professor marking the paper is sitting in his chair late at night with 30 papers to mark. There is a tray of stubbed out cigarettes beside...

Interesting. There was talk of the notion recently, in another thread, about the stability of epoxy package IC's, vs ceramic cased ones. I have seen a few epoxy package 74 logic IC's fail with open circuit inputs, and behaving, like TTL's at least do, as though that particular input was stuck...