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Repair Mistakes & Blunders - what bonehead move have YOU pulled??

DaveVoorhis said:
I was installing a bathtub surround kit in my first house in Canada, so that I could install a shower head above the tub. I carefully measured everything twice, test-fitted everything, made sure all the plastic panels aligned perfectly with the pipe holes before cutting, and then cut the holes for the hot/cold pipes.

Turned out I'd somehow cut the holes an inch to the right of where they should be. @£$%!!!

I went back to the store, bought another kit -- individual panels weren't available, at least not quickly -- and very, very, very carefully measured everything four times, test-fitted everything several times, repeatedly made sure all the plastic panels aligned perfectly with the pipe holes before cutting, went back and checked everything again, and then cut the holes for the hot/cold pipes.

I once again cut the holes an inch to the right of where they should be!

(Fortunately, the third kit went in without a hitch!)
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Damn, thats a best of. I can relate.
 
I had a nice NOS coke-bottle 6AS7G sitting on my desk, between a cat and a beer bottle. Nothing abnormal here. Then I moved, startling the cat, which sent the tube flying into the side of the bottle, promptly shattering the tube into oblivion. No beer was spilled.

Another time I found out, quite accidentally, that the socket I used for a type '80 rectifier in my power amps kinda-sorta will let the fat pins fit into the small holes, depending on the make of tube. After performing an annual health check on the tubes, I inserted the rectifier 180° from its correct orientation in the socket. Flipped the switch, aaaaand nothing. Stupid me put the filament directly across the 500V secondary. The bright side is, the plate fuses I chose worked beautifully, instantly protecting both the tube and the transformer from my bonehead mistake. Just a few minutes and I was back in business. It could have been a very bad day otherwise.

Fortunately I never had a capacitor explode that wasn't deliberately rigged to do so :). I did however, once witness a co-worker "venting" TWO brand new, large Sprague Powerlytics in a row, before realizing he had swapped the two physically similar, yet differently rated capacitors in the assembly he had built and was testing. Twice my attention was caught by a huge plume of smoke appearing over the top of the workbench followed by a series of profanities. Fingers crossed I won't make a cap mistake in the future... there's still time!

As to the heat shrink thing, how about soldering on a connector and patting yourself on the back that you remembered the heat shrink first.... only to realize at that moment that you forgot to put the backshell over the wire as well!
 
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mgosdin said:
Went to remove the bottom cover on my spare laptop ( DVD Drive has died. ) yesterday. Got all the tools out, found all the screws I thought I'd have to remove, even found a How-To Video on YouTube.

Thought I'd better scan thru the video. The tech moves a catch switch on the bottom, and off pops the cover.

I do a double take, play the video again, play the video a third time. Then I release the catch and ... pull the bottom right off. Easy Peasy.

Found out the ribbon cable is broke on the drive, buttoned it up, then put away all my tools. An hour plus invested in setup and put away of tools, 5 minutes to open and diagnose the problem.

I shudder to think what would have happened if I'd taken all those screws out.

Mark Gosdin
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It ends up looking like this
IMG_0179.JPG
 
I put together my CNC kit a couple of years ago. I spent a bunch of time fiddling with the X, Y, Z stepper motor setting making sure everything moved the right direction and correct distances. I started making test cuts using 1/8" 2-flute spiral bits in scrap plywood. Everything was working great, the circles were circular and the squares were square and the dimensions were good. The cuts were rough and I played around with the feeds rate and RPM but it never really did cut clean and would often smoke and burn the wood. So I reverted to something that I knew would work...1/4" straight bit at ~12,000 RPM with a 1/4" depth of cut just like my porter-cable plunge router. Fired it up and the result was total destruction of the plywood just like you might expect with a bit spinning 12,000 RPM in the wrong direction. I had neglected to verify the rotation direction of the 3-phase spindle motor when I wired it up
 
Following some advice on diagnosing a misfire, I grabbed a spark plug wire to pull it off, to see if the idle got rougher, or stayed the same.

While the engine was running. ZAP!

My friend once noticed that the rocker arms on his GTO were loose, so he tightened them all good and snug. His engine wouldn't turn over. After that, they would break, one by one.
 
Not my bonehead move but one I will never forget. Was sent out on a job one day to check on a brand new CNC lathe with an axis drive problem. Yaskawa axis drives. Drive module was throwing a code, looked it up and it said over current alarm.
Hmmm, nothing mechanically bound so I cleared the alarm and re-energized the drives. When I went to power it back up the boss of the shop was walking right behind me and the drives powered up with a huge explosion. I about **** myself! Bossman was not impressed either.
Seems the output transistors had somehow shorted and the drive PS protested in a big way.
Later that night after ordering new parts to be shipped over night I went back through the service manual that Yaskawa provided for the drive trying to figure out what went wrong. On the very last page of the manual was a sticker that was added as an after thought stating if you get an over current alarm "DO NOT CLEAR THE ALARM".
It would have been nice if a sticker would have been placed on the alarm code list. What bone heads!

BillWojo
 
Years ago I stumbled into a beautiful tube preamp with a switch for all different phono eq curves used at the time. Can't remember what it was, but gold faced. Maybe Fisher, but I can't find a similar example online. Went to clean it up with something I shouldn't have. Wiped all the lettering off in one swipe.
 
First receiver I tried to fix on my own was a Pioneer SX-850. I had to remove some transistors and replace them and in order to get to them I had to flip the phono board up and and back to get to the transistors I needed to replace. I replaced them and put everything back together and turned the receiver on but I still had the issue. This was my first time soldering so I wanted to see if that was the problem. I opened it all back up, flipped the phono board back so it was resting on the board under it and plugged my soldering goin back in. Except I didn't, I plugged the receiver back in by mistake. There was a loud pop and a puff of black smoke from where the phono board was touching the board under it. I brought it to a tech the same day and had him fix it.

The good news is that I've fixed several amps and receivers since then.
 
Relamping my Luxman R-1120 I nicked and broke the tuner string with the hot iron.....twice!

The best (worst?) was changing the driveshaft u-joints on my pickup truck outside on my fairly steep driveway. Just as I hammered out the last bolt I realized I forgot to chock the wheels....Oops, panic moment! I quickly jammed my boot under the tire as a wedge and hollered until the teenage neighbor came to the rescue. It was parked facing uphill so I narrowly escaped getting rolled over by the front undercarriage. Gives me shivers to this day.
 
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Washed the tuner glass of an otherwise perfect tuner in warm water & mild detergent. A second later and all the letters, markers and numbers were floating around in the sink like alphabet soup. Glass came out perfectly clear...

How many times have you made up a RCA lead only to realize the jack cover is still on the bench or the grip clamp is on the wrong side of the strain relief boot?
 
I replaced the power switch in my Yamaha CX-600. Not realizing at the time that it uses a non-latching switch to deliver a +5v pulse to the cpu to switch it on, I bought a good old latching switch and installed it. It took me a loooong time to figure out why it was behaving so strangely when I tried to turn it on. It either did nothing or turned on but did nothing useful because the continuous +5v on the start input to the cpu wouldn't let it do anything else.

I made a lot of mistakes with that pre-amp. It was a classic learning experience. It spent a couple of 6 month cool down periods while I let my frustration levels drop.

I couldn't figure out why almost all of the inputs would play at the same time until I learned that the n-channel FET's used for input switches were mostly shorted, allowing the signal to pass through all of the time. That only took me 6 months to figure out, with most of that time spent looking at that evil thing and deciding to do something else. And those 2SK105's are almost impossible to find.

I learned that while the SIP-9 op-amps have +V supply on both pins 1 and 9, and one can install a SIP-8 in pins 2-9, it still won't work because pin-9 is a dummy on the pcb and therefore there is no +V supply to the op-amp and this dummy didn't notice that for a very long time.

Cheers,
James
 
TomBig58 said:
Relamping my Luxman R-1120 I nicked and broke the tuner string with the hot iron.....twice!

The best (worst?) was changing the driveshaft u-joints on my pickup truck outside on my fairly steep driveway. Just as I hammered out the last bolt I realized I forgot to chock the wheels....Oops, panic moment! I quickly jammed my boot under the tire as a wedge and hollered until the teenage neighbor came to the rescue. It was parked facing uphill so I narrowly escaped getting rolled over by the front undercarriage. Gives me shivers to this day.
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I did the same thing relamping a stereo receiver about 25 years ago. It was a lasting memory. Restringing dial cords is not something for which I have any skill. 3 hours later it had a new dial cord. I am still extremely cautious whenever I need to solder near a dial string.
 
After changing the oil in my Accord and tightening everything down I realized I forgot the crush washer. Things got messy with my finger in the dike while I added the crush washer.
 
ah let's see how far I have to go back for my last botched repair.

Yesterday.

Have an electric string trimmer (yard work stuff) that wouldn't cut off the line properly, fed out all the line at once. Dig into it, found a spring mechanism which looked inadequate to catch the line reel after it advances on each auto-feed. Put in new firmer spring, fired it up. Line starts spinning out, wraps around axle and motor winds down to a halt with burnt motor smell. Brilliant. :/

Audio repairs? still working on building stuff first, will get back to ya later on those...
 
Grenadeslio said:
Warning, don't ever touch the lead on your multi-meter when the other lead is touching a 277V source, hurts like a bitch, don't ask how I know lol.
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Accidentally touched a bare contact on a clothes dryer circuit, 240V. If it had crossed to ground through me I wouldn't be typing this. Arm hurt for a day after that.
 
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