Mac Repairathon Part 6: Final stretch! The Mac Pluses.

[@Dukefazon]

A little tip for handling high voltages. This machine has a normal ON-OFF switch so you could just turn it on, plug in a power cable that runs through an extension cord with a switch as well. And turn the extension cord's switch to cut power from the board. It looks scary every time you turn the switch on the machine itself so maybe it's a good idea to keep your switching option away from the actual board.

[@only257]

Dukefazon kzbin.info/www/bejne/kKDYnp-enL-jqMU funniest movie ever made 📼

[@mndlessdrwer]

As long as the cleaning process doesn't damage components, I sincerely doubt people would criticize you for it, except maybe in jest. You keep doing you.

[@minombredepila1580]

This channel is amazingly good. First, you get astonished with how Adrian makes things easy and then you spent 20' reading the high-quality technical comments from the people. I love this channel !!!!!. Please keep the good work :-)

[@borayurt66]

Bad capacitors don't go up in value, they just seem to be up because of the way the meter uses to calculate their value. The meter applies a constant current and measures the time it takes the capacitor to charge up. Since the current is constant, the charge up time would be directly correlated to the capacitance. The larger the capacitance the more time it takes to charge up. When a capacitors ESR value has gone high, this resistance will cause a further current drop thus making the capacitor charge up slower than it should, this makes the meter think it has a higher value. Same applies for capacitors that has become leaky electrically. So, as a rule of thumb, if a capacitor is showing a much higher value than it's rating, (ie 25% or higher) it is always good practice to replace it. Great video as always, I love seeing old electronics coming back to life.

[@realnutteruk1]

40 years ago, my dad worked for DEC... he'd take me into work in the evenings, and I could walk into a room with 200 VT100 terminals in it, and by listening for that whine, I could point out the one terminal which had not been turned off!!

[@carnright]

Same but for walking into the computer room at school 😁

[@shmehfleh3115]

@@carnright I remember doing that in the Apple II lab in Elementary school. I thought I had a superpower.

[@gee-k5854]

Just binge watched all of the mac repairathon. I need more! MOOORE! P.s. good work Adrian, always love seeing your attention to detail on all of the machines you work on.

[@ast3663]

Hi Adrian, love your Mac repairs..you are very skillful and dedicated. This Repairathon is great ..I bet this mac is so thankful that it FINALLY got some new filter caps and cleaning job..after all these years..lol.

[@TedKekatos]

Adrian -- I dont own any macs, but watched your entire mac repair series. I enjoyed it very much. Great job.

[@andrethib]

around the 8 minute mark, when you were working behind the Mac and using the reflection in your monitor to observe the Mac screen, I had a childhood memory. Back in the late 60's/early 70's, TV repairmen came to the house; TVs then were big CRTs in even bigger wooden cabinets so they couldn't' easily be moved around. The TV repairmen would bring a mirror on a little stand to use to observe the screen while they worked on the TV from behind...

[@raggededge82]

The quality of these videos has gotten so much better. Another fun watch!

[@temporarilyoffline]

If its dumb and it makes you happy, then its not dumb. (Re cleaning the inside of the machine)

[@Yliannyx]

Younger naïve me made a massive mistake tossing a Classic II back in the early 2000’s. There wasn’t anything wrong with it except it needed the OS reinstalling and some peripherals. It was a spotless machine with a monitor with very low hours. That’s one of the mistakes I’ve made that I truly regret. Whoever picked it up at the recycling centre scored big time. By the way, the cap on the HT lead from the flyback is important. It is needed to stop oxygen getting to the anode connection and prevent corona discharge. Loved this series, keep up the awesome work!

[@bulldogcraft]

Don't feel bad. I did the same thing with a Mac Classic an external scsi hard disk, a TRS-80 Model 1 with all the peripherals (even light pen), a coco, Atari 800, 800xl, Atari 1040 ST, an Amiga with Toaster software. I'm back into Retro machines and it's costing me a small fortune!

[@SeanBZA]

Final board those capacitors you removed are dying, but were revived by the heat of desoldering them. Replace them, and readjust the 5V rail to get it spot on again.

[@vincef836]

I thought that too i also noticed the plastic sleaving on some of the capacitors has shrunk probably been running hot like you say the heat from removing the faulty caps has probably tempary altered the esr etc hence working for now

[@tomlindo2863]

This makes sense and to prove the point, where they where indicating as bad before he removed, I bet the test result would be different now.

[@DavidRickard1]

I've been trying to fix a Trinitron TV and I took a capacitor off the board to test because I was getting strange readings. Out of circuit it was fine so I put it back. I may have to re-test it now (it still doesn't work).

[@vincef836]

David Rickard are you testing the uf rating and also the esr Reading when I suspect capacitors I sometimes use a hair dryer to heat the board up if the set then starts up ok I will do a full re cap of that board

[@SeanBZA]

@@DavidRickard1 Trinitrons suffer from resistors going high in value as well, plus the usual GCS failures. In the areas of a GCS you will be best off replacing it with one of the multiple of retrofits instead.

[@krnlg]

Hi Adrian, I think when you measured the resistance of the caps (30:15) , you were also charging caps on the board (from the meter) when the value was rising gradually - and discharging when it was falling gradually (it would depend which way round you connect the meter). So the resistance you measure will have depended on whether the board was recently powered and how long you measure for. Love this series, just like I love your whole channel. Thanks for all your videos :)

[@Plainapple287]

I love this series, hopefully you’ll keep on with these Mac repair videos

[@GORF_EMPIRE]

It's never dumb to clean electronics off. Dust can be made of anything and could be detrimental. Great work!

[@grahamokely7233]

A good Mac Repairathon thanks. Adrian an interesting video would be one about organising your bench, tools, test equipment, cables, cleaning gear, spare parts etc even the location of the bin. Showing and telling why you put what were to optimize and make accessing things easier during a repair. Thanks Graham.

[@Dukefazon]

37:28 - I repaired a broken PS3 last year. I thought the PSU had issues but it was the regular reflow problem. There's a 400V capacitor on the PSU side of things and after I powered it off I was curious about discharging the cap. I heard it can shock you and it can be scary, don't work on stuff while holding them on your lap, etc... So I took a screw drived with a thick handle and shorted the 2 ends. The pop was so loud like a petard was blowing up in the room, it really gave me the willies, luckily it wasn't discharging through me, that would have been bad.

[@Echoes_AJ]

Adrian, those clicking noises come from the spark gap devices behind the battery compartment (they kinda look like ceramic caps). They usually indicate shorts inside the flyback secondary coil. The coil whine you heard was likely the flyback complaining. Those shorts are microscopic in nature and will tend to burn themselves out, "fixing" the problem. The flyback is still damaged, however, as it might have gone out of specs in the process. On the other hand, it can still happily work for years. It's a gamble. If it does it again, you have a clue where to look!

[@williamsquires3070]

No, the important thing about the X/Y-rated “safety” caps is the voltage rating, and substituting the right kind. As long as the capacitance is generally on the same order of magnitude as the original, you’re okay. They’re just for noise suppression. The A.C. Impedance of a 1 nF capacitor @ 60 Hz is around 2.6 Megohm. @ 120 VAC, that would create a leakage current of about 45 uA. And the capacitance of the one from neutral->earth doesn’t matter as there shouldn’t be any (significant) voltage there, anyway. HTH.

[@EsotericArctos]

Neutral to Earth can be important when you are dealing with GFI or RCD circuits as Earth and Neutral are not connected and can have a potential between them. There should not be significant voltage, but if you get any leakage at all across there, then you can trip the GFI device or RCD.

[@Walczyk]

Are thin film capacitors used for the high voltage rating? Always wondered why they are shaped that way

[@TomStorey96]

@@EsotericArctos in my house in the UK, the earth conductor is bonded to the incoming neutral conductor from the street, but splits off before the fuse box.

[@DShadowWolf]

@@TomStorey96 in the US there is a separate "neutral" reference that is used to get the nominal 120V w=plug voltage by having a split rail - the actual voltage at the breaker box, when ground referenced, is 240V. It means that there can be quite a bit of voltage difference between circuit neutral and actualy ground.

[@OtherWorldExplorers]

From a military point of view Your cleaning is needed. Visual inspection is the first step in troubleshooting. If the inside is dirty it makes it twice as hard.

[@tylerpferrari]

I've watched every one of your videos. I've never owned any of these retro computers but your work and your video quality is top notch. Thanks so much for doing them. I hope you continue to do this for quite some time, Adrian!

[@mariusberger3297]

The Plus is a delight to work on, simple and straight-forward

[@EsotericArctos]

I usually just resolder all connectors and the flyback transformer when I have these things apart just as preventative maintenance. I really don't like having to reopen them :). By the way, you definitely do need the Anode Cap and often the are sealed with silicon gel (which is usually what makes them feel sticky). The voltage is considerable and it will arc across to earth quite easily if tha anode cap doesn't seal nicely. That Machine 1 could still be the flyback, but maybe it is just an intermittent fault. Hopefully it will run a while before it dies again :) Thanks for taking us through this series of Mac restorations/repairs. It's been a fun journey.

[@MegaWildweasel]

we called that FM back in the Army. (frickin Magic. )

[@bitoxic]

38:55 Adrian! You have the midas touch on vintage electronics.... period! 😁👍

[@meebis7]

Thank you so much for making these! I wish they had been around five years ago when I had a Mac of my own that needed repair! Also, thanks for showing the close-up photo of a cracked solder joint; I didn’t know what those looked like so I never knew to watch out for them!

[@tubejay1]

Great series! I watched all of the episodes and enjoyed them.

[@carstendahlhjarup8783]

Enjoyed the series a lot - Thanks. I recommend you make it a habit of discharging electrolytes on power supply before working on the boards. 1. For safety and 2. protect the ESR meter from overload. I use 10R power resistor with two stiff wires soldered onto it (ressistor in heatshrink).

[@gallgreg]

Great close-ups of the cracked solder joints!! I remember trying to convince someone years ago that those are bad joints and not normal!! Congrats on getting all but one Mac working!!

[@scramble45]

Always best to put some HV resistant silicon grease under the anode cap. It serves multiple purposes. Keeps cap nice and keeps it from leaking HV. Great video as always though! Just trying to help.

[@doug834]

I love your videos Adrian. It always helps to relax as I watch you work. Plus I learn something new with each one. Thank you.

[@UpLateGeek]

Thanks for the WD-40 tip for gooey plastics. The Cisco 3750 stack cables we use at work go this way, and I always hate touching them when I have to work on those switches. To the point where I literally put on nitrile gloves to handle them! I've tried using IPA to clean them in the past, but it doesn't really work. I'm sure I can find some WD-40 to clean those cables though, so that should help make them less gross to handle. (And yes, we've still got 3750G and 3750-X stacks at work. Management keep rejecting capex requests to replace them, and they haven't failed yet so they must assume they'll keep working forever, despite being end of life and out of support! Even despite having several fail, we were just lucky to have spares from decommissioned systems so we could get them replaced within 24 hours.)

[@PaulinesPastimes]

Love the images of the cracked solder joints, fascinating. Great series. Cheers

[@tenminutetokyo2643]

My first Mac. One of Apple’s best machines, ever.

[@tekk9995]

Sweet! Maybe do a series on howto handle those high voltage retro components, like tubes etc.. What to look out for - the do's and don't. Great series!

[@BloodAsp]

Seriously needed/wanted!

[@BloodAsp]

@@dgpsf yes, this is what I see too, however surely there ought to be a presidence for education on nigh any topic rather than the CYA stance of today. It is KZbin after all, as you say, not a substitute for an apprentice ship. (However outdated that thought is.) Information should be free to access without the fear of persecution for either the student or teacher.

[@AxelWerner]

who knew that i would ever see one of those babies again like 30+ years later, still working like on day one. amazing

[@dragonhed123]

Awesome series Adrian really enjoyed it. It would be super cool to watch you do some apple 2s those have a soft spot in my heart because there was some in extended care at my school when I was a kid donated. Before and after school. I Played oregon trail, conan the barbarian, wheel of fortune, and wizzard of oz. Those were awesome times.

[@Renville80]

You almost have to give any old single sided board a good inspection. What I would recommend if there was a part that had a cracked solder joint and it has some weight to it, I would clean the part and surrounding board with isopropyl and put some RTV along the edge and the board to ‘anchor’ the part and keep the joints from cracking again.

[@MrSatellitehead]

Adrian Thank you again for taking your time to share with us your repair skills!

[@AzulChico]

It's been fun watching your channel. My family's first computer was a Mac Plus. It eventually developed a blank screen problem and hitting the side would usually restore the picture. I think the computer is long gone but it's nice to see these repairs. Thanks for the fun!

[@timrb]

21:55 DeoxIT mentioned. 22:34 DeoxIT appears 22:37 DeoxIT used

[@GarthBeagle]

21:54 "This might be a job for DeoxIt" Of course!

[@lightmagick]

I don't know why but I love watching old stuff being restored. I'd love to see one of these KZbinrs do a giveaway of something not working but including the parts they expect are needed to get it working. It's a weird idea I guess but I think it would be interesting.

[@DocNo27]

Awesome series, I'm really enjoying it! I still have my circa 1986 Mac Plus. And brand new analog and logic boards; bought both at different times to fix other peoples Mac's and then they backed out on me and I always kept 'em. I haven't fired it up in years - time to inspect the caps and give it a whirl! I have a passel of SE's too - time to break out the AppleTalk gear and fire up a game of NetTrek :)

[@stephenwilshaw3052]

I've enjoyed the whole series Adrian, Thanks

[@linksmith1057]

For cracked joints like those (and you are definitely right, those are cracked), I'd get out my big weller iron with its big fat tip which holds a lot of heat, and just reflow the entire board. But maybe that's only me. Also, new slogan for WD-40, "It gets the sticky off."

[@hiredgun7186]

13:21 the two electrolytics are doming on you, those may have to do with the B +

[@mrman17]

I noticed that as well - really surprised it wasn't picked up

[@hiredgun7186]

@@mrman17 I have rebuilt probably a couple hundred arcade monitors and its natural habit for me to replace even suspect 35 or 40 year old electrolytics lol. my eye just gravitated towards them

[@Renville80]

Even vintage radio and TV collectors refresh all the caps before even touching the power switch…

[@bjf10]

+/- 10% is a very common accuracy rating for caps, so 2000 pF vs 2200 pF is no biggie. I honestly wouldn't worry much about even doubling or halving the cap value, since this is a tiny noise filtering cap and not in any feedback loop (so it shouldn't affect stability of anything).

[@needfuldoer4531]

The eject button on that external floppy drive is for when you use it on an Apple IIgs. Macs always un-mounted and ejected disks from the Finder.

[@frankowalker4662]

I hate it when electronics fix themselves, you have no idea what was wrong or how long it will last. CRT TV's and monitors are very susceptible to dry joints, (cracks), due to the high voltage and heat they produce. Great series, thank you. They look good all lined up and powered on.

[@amberselectronics]

13:17 two bulging electrolytics on that analog board

[@Naturalbeachbum63]

Hi Adrian, Really loved this series of videos, you really know your stuff and watching them is a great way to educate myself if I ever have to fix my MAC SE's. Thanks so much

[@a4000t]

Nice work, not a mac fan but the trouble shooting and fixes apply across the board to anything.

[@methanoid]

Enjoyed this (and your other) video(s). You have a real talent for these things.

[@michaellanier7783]

The reflow could be on these boards could be from the automatic reflow machine not soldering and they were soldered by hand after inspection. I managed a pcb manufacturing process and this was common if the reflow solder started to get contaminated.

[@chloedevereaux1801]

the n key wasn't working on the typing test

[@valentinocolaon6060]

whining was probably caused by deoxit making stray capacitance in the connector. when it dried up it stopped. we in Europe use kontakt sprey. they are very similar but kontakt makes a lubricated and dry version of sprey so I use dry one with sensitive electronics

[@QuaaludeCharlie]

Thank you for the Mac Tour , I Learned some things , Game Play is Neat , Still keep the Zip Disk's around too :) QC

[@bricklearns]

Looking forward to the 3d printer stuff

[@acmild]

Regarding Farad value, Farad value is used to determined the current capacity of the Capacitor, AFAIK you could swap capacitor with different Farad value it "only" affecting the smoothness of the current flow, as long the Voltage value is correct because it will blow up if you put lower Voltage value than the current one. CMIIW, it was an old lesson for me back from the 8th or 9th grade era and never been refreshed. :D

[@threethousandyen]

The sticky stuff on the anode cap is dielectric grease. It prevents the anode cap from arcing. You should replace that grease.

[@achimboers]

Cristal quest is also one of my favorite mac games ever. I just recapped an LCII and played CQ in color !! Amazing it has always been in color like this ... Anyway, looking forward to that mac portable. I have one here in the closet I need to fix so I can use some inspiration.

[@sharebrained]

Mac #1 notion: initial cycling due to bad motherboard +5V connection - oxidization. Floppy drive still providing a little load, so power supply clicking was slower than when you powered up the analog board alone. Reassembly (and DeOxit?) resolved the bad +5V connection, providing enough load for the power supply to stabilize and the system to work.

[@sebastianwalker1081]

I have LOVED this series. Absolutely brilliant. It makes me want to try this - although I don't know what I'd do with the Mac afterwards!

[@BollingHolt]

Most excellent! Looking forward to seeing your dad's Plus with the accelerator board and external display port! And the Portable! I'll be interested to see what you come up with for the battery/power situation as I will likely end up copying what you do for mine LOL.

[@ScrotumPole]

yes the weird noise is called Stiction . It's the vibrations of the flyback transformer that is responsible for the horizontal deflection of the electron beam that creates the picture. You can figure out the approximate frequency by thinking like this: There are 525 lines drawn on a television and the display refreshes at a frequency of (roughly) 60Hz (it's actually a very strange 59.94Hz) BUT REMEMBER THAT IT'S INTERLACED. This means that the signal that causes the horizontal deflection has to sweep across the 525 lines of the screen 30 times per second (half the image is drawn in an interlaced pattern at a time). 525*30 = 15.75kHz This is why only some people can hear it. That's out of the hearing range for a large number of older adults. Why do transformers vibrate? I won't go into that, but you'll be familiar with the problem if you've ever been near a device with "60Hz hum" that didn't come from a speaker. It's the power transformer vibrating at 60Hz.

[@eDoc2020]

I'm not sure what frequency the Mac scans at, but I am sure it is a different frequency from TVs. I know these use 512x342 pixels, maybe 384 scanlines. Assuming 60Hz progressive, that would be 23kHz. Does anybody know for sure the scanrates the Mac uses?

[@uni-byte]

Happiness is a clean cathode ray gun, bang bang shoot shoot....

[@briangoldberg4439]

The sticky stuff on the anode is dielectric grease to prevent arcing. You should probably put some back.

[@charlieb9502]

I have noted something about the two capacitors that you pulled from the machine 1 analogue board. Those caps have gotten hot some time in the past. The vinyl label is heat shrink material. It is a tail tale sign that a electrolytic cap like that has over heated when the sleeve has shrunk down off of the top. Also on the one cap on machine 2 motherboard that was reading higher than the rated capacitance. That is also a tail tell sign that the cap is electrically leaky or has low resistance. BTW I enjoy your videos.

[@daw7563]

At 13:00 were those electrolytic caps flat on their top? I'd say from the video they are bulging and need to be replaced.

[@borayurt66]

Yes, that is also what I saw. Filter caps in an SMPS are under high load and their life span is limited. Any SMPS older than 10 years, best to replace all of them regardless.

[@lelandclayton5462]

I agree

[@Darknecros7]

It is good to clean all the dust out from inside. It’s much easier to inspect if everything is sparkling clean. Also love those old Macintosh pluses when EVERY chip was a DIP type. None of that quad flat pack stuff:). I wonder if that huge DIP chip inside those Mac pluses were the highest pin count of those back in the day?

[@ggoedert]

The reviews/repairs are great and I always enjoy them, but I have to say that the time lapse music always get me, they are wonderful... Kind of futuristic music found on 90s amiga or msdos demos, love them.... :-D

[@KennethPlaysOfficial]

Take a shot every time he says “Within spec” in the entire series

[@Zerkbern]

You mentioned Louis Rosman, who I like a lot… But, it's nice to watch board repair without an F bomb dropping every other sentence.

[@OzRetrocomp]

If you like wholesome board repair videos on (mainly) older Macs, check out Branchus Creations. No f-bombs, but there is the occasional interruption from a chicken or two.

[@MrGeerye]

Yeah I had to stop watching him because the whole whinging thing just got really tiresome.

[@carnright]

GeeRye branchus or rossmann?

[@Trevorodunne]

I love this series also I learn at lot Thanks Adrian

[@fnjesusfreak]

I think the eject button on the external floppy is for the Apple IIgs.

[@sampoturunen9337]

Thx Adrian for making these videos. These make my day 👍

[@75slaine]

Great series Adrian, thanks 👍

[@ddrmaxdan386]

For the second Mac Plus, if you kept the foam you can check the continuity as these can become conductive over time and could cause a short on the solder joints

[@fu1r4]

39:00 Of course it make sense. You mentioned that if there was no load you hear this clicking sound so obvious there was some bad connection to the motherboard. With bad connection it can sometimes be enough to pull the contact and put it back again.

[@TheBananaPlug]

Hi, you need an ESR table, google it to find lots of offerings. You can then see how ESR varies by capacitance and working voltage, not all higher values of ESR are bad. Hope that helps.

[@kd5byb]

YES!!! YES!!! YES!!! I LOVE REPAIRATHON!!! Even has me wanting to get a Mac like one of those to restore, but then not sure what I do with it or where I would put it...

[@projectartichoke]

On the last machine, it's possible that just moving that voltage adjustment pot may have fixed the problem. The pot's wiper can tarnish over time and the slightest movement will abrade that tarnish which only grows to a few molecules of thickness.

[@MarSAttK]

Hey Adrian! What about the portable? I would love to see a video on the repair of that one! Cool repair videos, keep them coming!

[@wishusknight3009]

With that second mac it may be good preventative measure to reflow the connections and what not. Even if they look good. Deoxit everything ect. Myself I tend to just recap the whole things anyhow as the caps eventually will go. But when dealing with so many machines that can be a bit much to deal with.

[@akhurash]

A lot of older switch mode power supplies might require some load to properly regulate. Linear regulators are the same but require much lower load.

[@EnderMalcolm]

The capacitance of the caps is not super important, that's basically just how much ripple it will get rid of from the AC lines. The more important part is the voltage. You're in the clear on how much voltage they can take, and in this case, they are actually safer. If you got a power spike there's way less chance of a 400 volt cap blowing than a 200 volt cap.

[@Aeduo]

The sticky residue on the anode cap is grease to prevent leakage/arcing from the high voltage. Not sure how necessary/important it is or if it's just extra safety, though. Maybe in high humidity environments it might make a difference.

[@TJCeltic]

I sure would love to have one of those Mac PCs

[@rwdplz1]

Congrats! Time to make floppy gears and max out the RAM on all the machines!

[@vhfgamer]

Sometimes heating up a component with a soldiering iron (while removing it for testing) will change the value and make it go back into spec. Sometimes just desoldering and soldering things will fix it. Of course it won't last... so then you'll be right back to trouble shooting again.

[@JBFromOZ]

thanks for sharing, awesome info for use when I get to my old stash of Macs

[@Stefan_Payne]

Yes, Y Caps are between L1 and Earth and N and Earth. And, in theory, you can leave them out. A PSU Technician once told me that they aren't really input filtering but filter the stuff from the device going to the grid. So you could, in theory, leave them out. But its better to have them. As for replacing them, I'd not worry much about X/Y Caps much as it doesn't affect the circuit in any way whatsoever...

[@Johnny-es9xg]

Hi Adrian. Don't worry mistakes happen .I too I got electrocuted busy fixing a old ATX power supply. By mistake I put my hand on the MOSFET heat sink on primary while touching the case when it was on. Got a good shock and tipped the earth leakage on the electrical board. After that I had a good laugh at myself for being so stupid.

[@SiD3WiNDR]

Well doe Adria, that first machie's keyboard was ideed workig great!

[@hoverbeaver]

Careful with using windex/ammonia based cleaners on the "inside" part of CRTs. You can damage that aquadag coating. Always do a test with a q-tip first. Some tube manufacturers used water soluble paints, and then you end up having to repair the conductive coating. That's a painful lesson from arcade restoration.

[@ROBINHOOD2098]

if you have a crt tube that has a dark screen before changing it take a screwdriver and take the handle and gently tap the crt neck behind the yoke while crt is turned on incase there is a phosphorus particle short from laying crt with the screen facing up.

[@geoffreed4199]

the sticky at the anode is often silicon dielectric grease. also it looks like you have bulging electrolitics on the analog board of the first (platinum) mac plus

[@iamdarkyoshi]

Gahh, the "wait why does it work now" fixes are the most irritating!! They'll gain your trust and then stop working when you least expect it lol Another great video though, nice to see these machines working again!

[@ghwizz]

Is it worse when you don't know why it works, or when you don't know why it's broken?