What was your easiest repair ever?

[TerraHertz]

To be more precise, what was your highest ratio of repair ease to value of equipment?

This was mine, a few days ago.
I was given a very cute, modern, small LCD projector, a DELL M900HD. It had been thrown out by a large institution due to being 'faulty'. It powers up, then after a few moments says "fan fail" then "over-temp, shutting down". Which it does.

On opening it up, this is what I found. There are several fans. They are not even screwed in, just slid into slots, with foam tape to prevent vibration noise. With the cover off they can be simply lifted out.
The two largest fans (still tiny) have rotor shafts that are only held in the sleeve bearings by quite weak plastic clips on the shaft end-ring. Mostly they are held in place by the field magnets.
Someone had bumped the projector sharply enough to dislodge one of the fan rotors. It had slid out of the sleeve bearing and wedged.

I just popped it back in, and screwed the case lid back on. Four screws. That was it. This is a really nice projector, very small, with lots of inputs, and even WiFi video input. Also the lamp is LEDs, so no short-lifetime HID lamp to fail.
In the pic showing it running I have the brightness turned down to the very lowest setting.

[nidlaX]

For me, it's a toss-up between my Telulex SG100/A (output SMD fuse), my HP 6543A (mis-aligned LCD), and my DE-5000 (input protection diode).

[DTJ]

Not so much electronic but it's used in my electronics workshop......

A large reasonable quality air compressor was thrown out for verge rubbish collection. I tested it and it didn't work. Pushing the overload button on the electric motor fixed it.

[Muttley Snickers]

This Dyson vacuum cleaner pictured below, I was driving home not long ago and happened to see a Dyson box out on the nature strip so I stopped to check it out, I noticed sticky tape over the power switch and in the box with the cleaner was all of the accessories. I had to take it.

I don’t normally scrounge this type of stuff but at the time we were looking to upgrade our existing thing that sucked, I happened to have a latching switch that fitted and gave the unit a good clean, it’s been great ever since.

[bitseeker]

Does a car count as equipment? Plenty of electronics. Well, I once had a Honda Accord and its Check Engine light came on. Pulled out the service manuals and based on the LED blink pattern on the ECU, the flow chart indicated a reboot to the ECU. Did that. Fixed. Problem never recurred.

Laptop that wouldn't boot anymore. Removed dead battery. Booted and ran just fine thereafter.

Let's see, what else. A dead 27" computer monitor. Classic fix with a $0.29 capacitor.

[iampoor]

I bought a bunch of audio gear "as-is" (owner didnt remember if it worked or not, and couldnt be bothered to test it). I made well over 500$ on a rack mounted spring reverb that had 1 open capacitor. That was a good day. 

The only piece of gear I couldnt fix was an Eventide 910 digital harmonizer. VERY cool piece of gear, unfortunately, almost impossible to economically fix.

https://valhalladsp.com/2010/05/07/early-pitch-shifting-the-eventide-h910-harmonizer/

 

[CaptainObvious]

Mine was probably when I was working at my old IT job.. they couldn't find out why this motherboard wasn't booting (was "recycled" by the customer... with first gen i7 and 12gb ram) lol I asked if I could buy everything for $50 instead of our company recycling the parts from it.. figured the ram was worth it if nothing else.

The fix? Installing a video card. They were trying to use the on-board VGA adapter, but the first gen i7 (960, to be exact) doesn't have an embedded GPU, lol... Still using it to this day as a file server for home use! (And I've long since left that company)

[george.b]

I work at a laboratory in the University, where someone once plugged a 110V printer into a 220V socket - not that unusual in a country where you have two voltage standards, one is twice the other and the sockets are the same. 
Since it was a color laser printer with brand new toners, I decided to try and fix it - only thing that had blown up, other than the fuse, was a MOSFET, which I replaced with another one, scrounged up from scrap. Good as new!

[bitseeker]

two voltage standards, one is twice the other and the sockets are the same. 

That's brilliant! There are so many things we learn about on the EEVblog forum.

[iampoor]

I work at a laboratory in the University, where someone once plugged a 110V printer into a 220V socket - not that unusual in a country where you have two voltage standards, one is twice the other and the sockets are the same. 

How do you tell the difference? 

[george.b]

Ah, let me clarify: it's not like both standards are there (officially) side by side at one given place, it varies according to location. For example, where I live we have 220V line voltage. One of the states neighboring mine has 110 (actually, 127, but we commonly call it 110), but someone living there could have their house wired with 2-phase 127V to get both 127 and 220V in the same household. Then you have to remember or mark which sockets are 220, so you don't blow stuff up, since we don't have different socket types for different voltages
Getting both voltages where I live isn't that simple, as we'd get 380V line-to-line voltage. Because of that, it's not uncommon for people to have transformers at home, and when a relative comes to visit, the question "is it 110 or 220?" usually comes up well, not as often nowadays, when most things you'd bring with you when visiting a relative have switching power supplies that can work with both, but still - power tools from one state, for example, could be useless in the next state if you don't have a transformer for it.

Edit: I found this nice little map that actually shows the different voltage areas within Brazil. You can see my state as an island of 220V surrounded by 110V

[BMack]

Master power switch turned off, get them several times a year. Bad power switches, messed up menu settings, batteries in remote, updating firmware, bad belt, bad caps...love the easy stuff, wish I got more of it! ...every customer seems to know that their unit is easy to fix anyway.

[Kilrah]

Hmm...
In the low end I'd say a simple halogen lamp that I saved from the dump collection point as a kid, and got to work again by just cleaning the slightly corroded lamp holder. Little $ value, but it was my bedside table lamp for several years, and I was surprised to find it still in use when I recently visited my parents after they made changes in their house, that's about 20 years later.

More recently a laptop whose owner got frustrated about the slowness and punched, destroying the HDD. He bought a new laptop obviously not to repeat the slow experience, I kept the old one and put it back in service putting an old (IDE) HDD that had just been collecting dust until then. Obviously not a crazy thing but it works perfectly fine, and is good to keep around thanks to hardware serial/parallel/IR ports etc as well as all modern interfaces.

Many more as a kid, I don't remember the details of what/how, but many times it was just a bad contact solved by shaking or cleaning things a bit, sometimes a cracked solder joint, broken rubber belt etc. Before my first job I barely ever bought anything and just equipped myself just by doing usually minor repairs on things people were throwing away.
Best way to learn things too since you're much less concerned about potentially breaking expensive stuff...

[CJay]

This Dyson vacuum cleaner pictured below, I was driving home not long ago and happened to see a Dyson box out on the nature strip so I stopped to check it out, I noticed sticky tape over the power switch and in the box with the cleaner was all of the accessories. I had to take it.

I don’t normally scrounge this type of stuff but at the time we were looking to upgrade our existing thing that sucked

Vacuum cleaners are meant to suck.

[CJay]

Does a car count as equipment? Plenty of electronics. Well, I once had a Honda Accord and its Check Engine light came on. Pulled out the service manuals and based on the LED blink pattern on the ECU, the flow chart indicated a reboot to the ECU. Did that. Fixed. Problem never recurred.

Laptop that wouldn't boot anymore. Removed dead battery. Booted and ran just fine thereafter.

Let's see, what else. A dead 27" computer monitor. Classic fix with a $0.29 capacitor.

Mine was a car too, £1900 book price GM people carrier with manual gearbox, the owner had been told by an 'expert' that the clutch had gone and would cost around £1100 to replace so he sold it to me for 'scrap' for £250.

The fix, 10 minutes with a pair of spanners, a wire brush and a dab of grease.

The pedal had rusted and siezed around the pivot bolt.

Ten years later and she still works .

[tautech]

Tek TDS210, display not working and given to me by an EE that couldn't/wouldn't even take the time to have a look at it. 
All the visual indications were there that is was booting, buttons illuminated etc.
No display backlight was confirmed with the usual bright torch to the display trick.
PSU checked OK and a scope probe held close to the discrete primary side oscillator of the backlight HV supply confirmed it was not oscillating. 30c resin dipped 0.47 uF gumdrop cap fixed it. Replaced cap measured pF's. 

Tidied her up, supplied a pair of new probes, put all the manuals on CD and sold it a few weeks later for good coin. 

[VK5RC]

An older HP psu,  sold as does not power up,  flicked the switch to 230v and she worked,  suspect the switch was a bit intermittent but still works on 115v now as well.

[Jwalling]

A TDS784C on eBay for $300 or so that "wouldn't power up." Fault: The soft power on button had gone high resistance. a dab of conductive paint fixed it. 

Jay

[Rerouter]

Was given a pallet (300 units?) of overload proof industrial constant current /voltage power supplies, under the assumption they where all faulty because the first 3 did not work. So had been sitting in a corner for a year or so.

Pulled the first one out of the packet, and indeed did not power up, looked in the packet again, and sitting in a small zip lock bag the fuse , was a great pay bump for an apprentice.

[Kjelt]

A Delta PSU 300VDC-5Amps, replaced one opamp and done.

[TiN]

HP 3245A. Wiggle some cables, and it was back online like new. I was washing front panel and taking photos much longer than actually getting unit to work..

[nctnico]

To be more precise, what was your highest ratio of repair ease to value of equipment?

I recall a keyboard with some burned fusing resistors and a TFT monitor with the same problem which where easy to fix. Or a PC which only needed a new coin cell battery.
My best one is problably this one: Two decades ago I got a defective HP6002A PSU (200W 50V/10A) and the owner said it had overheated and shorted a battery. He wanted to get rid of it because he was sure it was way beyond repair. However all I needed to do was bridging/repairing some burned out PCB traces and resolder some wiring which HP had goofed up. That PSU still works today!

[w2aew]

A Kenwood TS-940S ham radio HF transceiver refused to transmit on single sideband.  Removed, cleaned, tightened and re-installed the audio cable from the microphone to the main PCB - solved.

[Kleinstein]

At university we had an rather old Hitachi electron microscope running from an 230 to 110 V transformer. One of the circuit berakers got bad due to an terminal screw that was loose and got hot and thus tripped early. Luckily they had a second output with the same size fuse, but much lower load. So just swapping the two wires and add/change a label did the trick.

Another one was a controller for an vacuum pump, kind of a 10 V 70 A power supply, that had just a micro crack in a circuit board. A little hard to find, as one could not see it. But fixing it was easy (no protective coating) by just short piece of wire.

A slighly more tricky one was a HP computer (some 7000 series UNIX workstation) with burned network interface (likely due to a broken external AUI to ethernet converter). It was just replacing a fuse. We had a similar problem before, while the unit was still under warranty: a technician came from HP and changes the mother board. Could have been the same problem before.

[TheSteve]

HP 8714C 0.3 - 3000 MHz network analyzer - flipped the 110/240 selector switch back and forth a few times and it came to life. So the fix was 10 seconds but I still spent 5+ hours cleaning it and then recapping the power supply as part of preventative maintenance.