I'm new to this forum, and fairly new to some aspects of vintage computer repair even though I've used 'em since they weren't vintage. I've dug through these forums and others but not seen an issue quite like the one I'm dealing with.

I've got an SE/30 that, until this past year, I didn't even know worked - I was given it along with several other partial compact Macs by a friend years ago, and they sat in a shed that wasn't terribly watertight, so when I dug them out for a project, there was plenty of surface rust, and the mainboard was a bit crusty looking, but fortunately not battery bombed. After a reasonable cleaning, and wiggling the ROM SIMM a bit, it came to life, and it's got an external video card in it, even!

In the process of making it more presentable, I've swapped the analog board for a spare from an SE that had a good flyback transformer, recapped THAT board, the power supply and the mainboard with kits from Console5, put a new battery in and replaced the HDD (which I managed to get working enough to back up) with a BlueSCSI. It now boots (and chimes) and runs reliably, and for the most part, looks great.

Except there's noise in the video that gets stronger as it warms up - after about ten minutes, it reaches a peak and stays there. I saw it surge with HDD activity while I was working on recovering the files that came with it, but that part isn't in the machine. I've tried replacing the HOT and reflowed the analog and CRT boards, but am unsure where to look next. The caps on the mainboard leaked at least a little, at least judging by how they looked when I removed the old ones, but I don't see much of anything that looks like corrosion beyond all the solder on the board being dull and slightly soft (fuzzy?) looking - no green crud. All of the pads came clean easily and everything looked good to my eyes otherwise. I swapped the CRT board with the one from the SE, and the noise changed a bit but didn't go away. The only consistent thing I can to to reduce the noise is to turn down the brightness - the brighter it is, the stronger the noise is. The pictures attached show this at normal brightness (the noise moves randomly like static) and one turned almost to nothing, edited to be more visible. I also haven't seen any rogue solder or bridged connections, though it's always possible that I missed one.

Would the CRT board be the next thing to investigate, or should I still be looking at the motherboard or somewhere else? I've always been good to hang parts, and now I feel more confident I can solder them, but circuit-level diagnosis is still kinda new to me.

Yeah ripple current and ESR matter allot for what we do :) must have for any of us nerds is a LCR meter for testing the boogers !

In regards to good quality LCR meters, unless you're going to pay more than $1,000 for a benchtop meter, the absolute cream of the crop for hand-held in a reasonable price range is the DE-5000, which I personally use all the time:


I first learned about it some years ago on the EEVBlog forum. A lot of people use it. It's pretty great.

With that said, I've had caps which were old, never leaked, and measured good, yet they failed in-circuit. So the meter can be a useful guide, but it's not a perfect solution for finding bad caps all the time.

>> JDW said:

I have nothing against Console5. Nothing. I respect the seller for the service he provides to so many. But I'm one of those really finicky EE's who really wants to know ALL THE SPECS of the caps before ordering, and Console5 doesn't provide that level of detail. Again, not biggy for most buyers, but a big deal for me. So like you, I also select individual caps from Mouser, which gives me complete control over the entire process and lets me choose the best caps for a given application. Click to expand...

I can see why cap kits can be very convenient but I am cheap, they are usually a bit more expensive because the hand picking is done for you. So I tend to order enough parts for several jobs so I can claim the free shipping.

I did initially order the wrong sized capacitors on the primary side for the Sony PSU.. whoops, they wouldn't fit. If only I had looked at the cap list that you had posted online for the various components before ordering.

For a single project one-off, Console5 is cheap. It's hard to beat it. But yes, buying several recap jobs' worth of parts at once from Mouser or DigiKey to get free shipping can work and get you low prices too. You just need to watch out when using SMD types like Polymer Tantalum because they have to be installed within a certain amount of time, as I describe at 15:10 here:

>> JDW said:

In regards to good quality LCR meters , unless you're going to pay more than $1,000 for a benchtop meter, the absolute cream of the crop for hand-held in a reasonable price range is the DE-5000, which I personally use all the time: Amazon.com I first learned about it some years ago on the EEVBlog forum. A lot of people use it. It's pretty great. With that said, I've had caps which were old, never leaked, and measured good, yet they failed in-circuit. So the meter can be a useful guide, but it's not a perfect solution for finding bad caps all the time. Click to expand...

Not bad, personally i have 2 hand helds, one from Applent (AT826) it was around the same price. Served me well for 10 years now. and i just got a FRNSI LCR LC1020E, very cheap and thus far it seems pretty good. for complex issues and suspect caps i use a Chinese Tonghui TH2840A, boot is slow, its noisy but definitely accurate and fast once booted.

>> JDW said:

Well, @basslinemz has only posted twice in this thread so far, so he does need to chime in with answers to your questions. But his opening post says he used Console5, which isn't a vendor I've personally used in the past, but the fellow does make his living selling cap kits, and I've never heard any rumors he sells "old caps," so I suspect the caps used were pretty new. What's really blowing my mind is that in his 2nd post in this thread, he mentions having swapped even the CRT too. So he's swapped not only the Analog Board, and not only the CRT Yoke board, but even the CRT! What in THE world is going on. There's something we're not being told here. I've been on forums for decades and never read a story quite like this! Click to expand...

Apologies for not responding, but troubleshooting has been on hold while the computer gets a little real-world exposure between major holidays (it and some friends are hanging out in an elementary school gifted classroom, as part of a rotating display of vintage tech for kids to try out and ask questions about). As the problem seems to stabilize at a certain point, it has an external monitor they'll want to look at anyway, and they're not going to run the computer for hours at a time, it should either be fine for the time being or finally fail to a point that gives us a useful hint.

I can't say for certain if I noticed the issue before the recap work, as I was mostly trying to get the external video card working reliably. I recall a noisy display at one point, but that was with the original analog board shortly before the flyback audibly crapped out and I switched to the one that's in it now (also the one that was cleaned and recapped).

And yes, I recognize that this situation is novel - that's why I created an account to ask questions here, hoping someone had a lead I could follow because the Googles, they had nothing. I wish I had more to tell you - I know it's isolated to the horizontal plane, it starts out very weak when cold and increases as it reaches full temperature, it's not affected by replacing the CRT or the CRT board, and that a questionably functional HDD connected to the device can make the same kind of noise appear when there's disk activity.

(classroom pic attached because why not?)