I’m an idiot!

[agardiner]

Yes, we have all done it. But this thread is certainly entertaining!

[eddie_ce]

Many years ago, while installing a brand new 25W 86MHz trransmitter for the fire service I decided to check the voltages on the backplane.

A slip of the meter probe and there was the magic smoke and a smell of overheated fibreglass pcb. A visual inspection showed no damage, of course not, the power supply tracks were in one of the inner layers of the multi-layer board and the 12V supply track had decided to give up.

Oh well, had to fork out for a new backplane, but luckily no other damage to the expensive kit was caused. Just one of the silly or careless mistakes I have made over the past years.

While a young TV tech. I persuaded the boss the buy one of the first Philips DVMs with red 7-segment display, not a cheap piece of kit. I learnt the hard way that it was better to keep the probes well away from the line output stage. The repair was not cheap.

[Philips210]

As a youngster. I was wiring up some flourescent tubes in an art light box that I made and forgot about including the ballast chokes. When the mains was applied there was a small crack and two wrecked tubes. I think they call it learning by your mistakes or something like that!

Regards,
Symon

[Dave Moll]

Originally Posted by Philips210

I think they call it learning by your mistakes or something like that!

And the real idiot is the one who doesn't learn, and keeps making the same mistake!

[lightning]

When l first started in TV repair l bought an Oscilloscope from RS, because my colleague said "you can take away all my tools, but don't take away my oscilloscope"

So, the first TV l had for repair with frame collapse l fired up the Hameg HM203-6 and set to it with the probe.

On about the third pin the probe slipped and went between two pins. The top blew off the chip and hit the workshop wall.

"Well, at least that TV has a definite fault on it now" said the other engineer.

[agardiner]

Oh that has reminded me of a similar incident. Many years ago I was showing round a work experience lad in the TV workshop. A colleague was working on a TV; power applied as he worked on it.

I was explaining to the lad that you should NEVER touch anything in the back of one the TVs as they were dangerous and that the engineers were very experienced. The engineer who was working on the set turned round and said that he would demonstrate the danger. He picked up a neon screwdriver and headed for the EHT cap. He slipped though and the screwdriver shorted out the EHT (set running remember), causing a massive bang, large blue sparks and a rather frazzled looking engineer, along with a dead set.

'See' he remarked!

[PsychMan]

Ive made hundreds. Few off the top of my head

- Accidentally sticking an EL84 into the EZ81 socket of a radiogram chassis. Funnily enough there was HT just a little low. Once the EL84 warmed up there were some fireworks. Still worked as an output valve though

- Destroyed a Germanium transistor in a jukebox through clumsy application of a scope probe

- Tripped my RCD working on a live chassis radio by touching an earthed soldering iron pin to the chassis. Then falling over finding my way to the house in the dark to flip the RCD back on . This has actually happened so many times now I always use an isolation transformer with live chassis radios. I'm pretty good at cutting power, not so good at removing the plug from the socket!

Adam

[SiriusHardware]

Although statistically improbable, there must be a technician / engineer somewhere who really has never made a mistake. If so I would like to know his or her secret.

For everyone's sake, I hope they happen to be working in something mission-critical like medical instrumentation or aviation.

[G6Tanuki]

We all make mistakes... My most expensive one being to accidentally hit 'transmit' on a piece of rather powerful VHF transceive gear when its output port was connected to a hired pulsed noise source used to optimise S/N ratio in the receiver.

Said test instrument really didn't like having 250 Watts of RF shoved into it, and I had a lot of explaining to do when returning the now wrecked noise source to the rental company.

[peter_scott]

If it's any consolation I'm currently doing similar silly things with a 5 volt rail in my old Marconi TF2370 Spectrum Analyser. The 2N3055 series transistor looked good so I replaced the uA723 regulator but still the same result showing about 0.5 volts output. I then thought I'd reduce the load to see if the regulator was just current limiting but I put my series resistor in the wrong place and when I next stuck the scope on the 5 volt rail it was showing a ripply 8 volts and retaining that voltage after returning to normal circuit! I'm just hoping I haven't killed a load chips.

Peter

[Lucien Nunes]

I had repaired the ignitor in a xenon projector lamphouse and was about to fire it up for the first time. I needed to see the PCB to make sure nothing was flashing over, so had defeated the interlocks on one side of the lamphouse and left the door open. I secured the area against unauthorised access, connected the mains and operated the ignitor. Just as I pushed the button, the leads of my Fluke DMM moved. They had been parked somehow, around the dowser handle and port, I should have removed the meter entirely before testing but didn't. At the very moment the ignitor fired, the leads flopped down and a spark jumped across from the lamp positive stud in the geartray.

That meter was almost part of me, had followed me around 18 countries over nearly 25 years, survived being buried in the Sahara, falling in the North Sea and the Thames, ridden around a baggage conveyor naked when my toolbox split open and had accidentally gone to Japan without me. It was fitting that the first incident to disable it would be a 40kV flashover, not just a broken range switch or something mundane. It will be repaired.

[medge799]

My personal favourite: I ran up an old radio with a ratty old mains lead to see what it would do. It worked sufficiently well that it was worth continuing, so I turned the set off and removed the said lead with a set of snips. Should have turned it off at the supply end, not the radio end! House mains tripped out with a bang, left me shaking with 'what could have been'.

Posting these 'events' here is excellent. We should learn from the mistakes of others was we don't have time to make them all ourselves...

Mark

[bluepilot]

Many years ago we had an Interdata 70 minicomputer. We had a service contract with Interdata but as time went by we became more and more convinced that we were being ripped off. Eventually we decided that we could maintain it ourselves and save money. The plan went well right up until the first attempt to do anything, at which point the resident hardware man managed to connect one of the signal lines to far more volts that were good for it. Lots of smoke appeared and the machine stopped working. There were blown chips on every board in the machine.

Luckily it was all fairly standard 7400 series logic and replacement chips were readily available. A couple of days later and it was all working again.

[Sideband]

Originally Posted by fetteler

Let's not make too much of it, everyone has 'sub optimal' days!

Steve.

....not helped by too much alcohol and being only 18 at the time! My first 'goof' was one Christmas eve although the problem didn't actually manifest itself until about 6 months later.

My first job at a small family-run business. I was tasked with finding the cause of a frame collapse on a 17" Pye TV. Being Christmas Eve there was a certain amount of urgency to get the last few remaining sets out. Nice easy job, cathode resistor, bypass electrolytic and a new PCL82 and the frame on the Pye Pioneer was restored. The chief engineer tapped me on the shoulder pointing to his watch which indicated lunchtime and a motion to join him down the pub for a traditional Christmas pint...or two. I decided to leave assembling the Pye set until the return from the pub. An hour and a half later with three pints of Youngs Special inside me and a slightly muzzy head, we returned to the workshop to finish off the last couple of sets. It took me no time at all to reassemble the Pye set and a final test showed all was well and it was duly returned to the delighted customer. Fast forward 6 months and the Pye set once again appears in the workshop....different fault of no sound. A quick check proved the customer was right so turned the set off and proceeded to remove the back. As the back came away, there was a clattering sound and a strange whooshing noise as the chassis together with the neck of the tube fell out and dangled on wires....!

The story had a happy ending. The chief engineer who saw the funny side of it, when he had recovered from laughing, set about helping me sort it all out. He also handed me a box of screws which should have gone back in the Pye set on Christmas Eve....! He'd been wondering where they came from for 6 months.....! He found a good tube in a scrap set and I set about fitting it and then sorting out the original fault of no sound (which was another PCL82 and cathode resistor). I made absolutely sure that all screws were fitted this time but it was a 'sobering' experience!

[radiograham]

Originally Posted by medge799

My personal favourite: I ran up an old radio with a ratty old mains lead to see what it would do. It worked sufficiently well that it was worth continuing, so I turned the set off and removed the said lead with a set of snips. Should have turned it off at the supply end, not the radio end! House mains tripped out with a bang, left me shaking with 'what could have been'.

Posting these 'events' here is excellent. We should learn from the mistakes of others was we don't have time to make them all ourselves...

Mark

I did exactly the same thing around about 1977. I can still hear my dad "what the bldy hell have you done now"

Graham.

[radiograham]

While I am on this subject does anyone remember a certain "Brainless Bertie" he was a sort of cartoon character in a trade mag in the 50's/60's.I cannot remember which one. I have some copies somewhere must dig them out.

[jhalphen]

Hi to all,

Anecdote #1:
Circa 1968, i was +/- 15.
Had purchased a Kyoritsu KEW-3 Scope from RIM Electronics supplies in Germany while on a language school trip.
The Scope is all tubes 3 MHz bandwith, no DC, no calibrated positions, very basic.
While poking in the innards, wanted to measure the CRT filament voltage, only 6.3V, right?

Well knew nothing then that CRT Filaments & Cathode are at high negative potential and received the full 1200V EHT when my multimeter test probe slipped & touched Fil pin with bare finger.

Was a good lesson! purchased a book on CRTs & Scopes and started filling in the gaps.

Anecdote #2:
1970. Was given an all-tube non-working 1967 25" SECAM colour TV, an Oceanic TV-600 (30 valves, transistorized UHF tuner).
Purchased a thick book on colour TV theory, the set's schematics and got to work.
The set had 4 failures. Took my time, 4 months, learned circuit by circuit & fixed it.
Decided that for reliability would replace with all-new H & V scan valves, EHT shunt, etc.
Local dealer sold me RFT valves made in the DDR. The EL519 & GY500 were shorted from defective QC.
When the plates started glowing red, boy did i switch off fast! no damage.
Purchased only Philips, Telefunken, Valvo valves thereafter.

The TV ran faultlessly until 1978 when i moved and purchased a new 12" Trinitron with my first salary.

Best Regards
jhalphen
Paris/France

[Radio Wrangler]

We all am idiots - Fortunately in different ways, and at different times, so that we can all cover for each other

A group of synchronised idiots is a fearful thing.

David

[Refugee]

I can remember helping to remove an internal partition wall.
There was a socket strip on it that clearly looked like a retrofit.
I lifted a ceiling tile and sure enough there was three wires in the box.
The wire I wanted to remove was on its own with the other two on the other side of the block. I took the short cut of undoing the screws and pulling it out.
I was informed with a bang that the spur was something else and that there was another terminal block hidden under a flap of itchy rock wool.

[bigfathairyvika]

I quite regularly forget to put my meter lead back into the volts socket after measuring current and the next volts measurement results in a short circuit.
Not good when checking a car battery voltage.


Recently purchased a dc/ac clamp meter to try and resolve this.