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

Back in '76 while in the military I was working at a receiver site in Italy and had a receiver on the bench doing an alignment. Of course the unit had to be powered up to do this, and somehow I managed to touch 200 volts that threw me about ten feet across the room to the floor. It happened so fast I wasn't sure what happened. One moment I was on a stool watching the o'scope, then the next I was on my a$$ on the floor ten feet away. No pain, nor any memory of the flight. Was just there, then was here.
 
I was doing some tune up exploration of my Pioneer SA-9500II. I had turned off the power and was starting to check some wiring in the amp section and I accidentally allowed my probe to touch one of the output's wires and grounded to the heat sink and to my astonishment I was greeted by a serious spark. It blew the output and enough things on the amp card that I ended up doing a full rehab.

The lesson to be learned here is don't forget that the power supply filter caps hold a charge for quite a while; so, from then on, I kept a meter clipped to the caps so I would know when they were discharged after powering down. It was a hard learned lesson.
 
I bought a nice tweaker (plastic adjusting tool) as recommended by Avionic. Used it for the recent adjustment of a Kenwood L-07M. First one went fine. Second one...adjusting the rail voltage, the first adjustment on the top of the board, clips on the bottom of the amp and I'm looking at the meter and bottom of the unit and see a flash. Damn metal clip on the tweaker touched a heat sink for a board mounted TO-220 or something and I thought the world had come to an end. Sat there and called avionics' tweaker tool all kinds of names. Finally got it on the bench because I was going to order parts and rechecked the fuses. Seems I missed the previous check when reinstalling the fuses as I put the 100mA fuse in the 5A position and vice versa and they are adjacent. Did this when originally checking the fuses in the unit during/before the recap.

The other one was the early meter check without mini-grabbers. Popped a resistor in a sony turntable. Mini-grabbers are a main part of the meter system now.
 
KingBubba said:
I was doing some tune up exploration of my Pioneer SA-9500II. I had turned off the power and was starting to check some wiring in the amp section and I accidentally allowed my probe to touch one of the output's wires and grounded to the heat sink and to my astonishment I was greeted by a serious spark. It blew the output and enough things on the amp card that I ended up doing a full rehab.

The lesson to be learned here is don't forget that the power supply filter caps hold a charge for quite a while; so, from then on, I kept a meter clipped to the caps so I would know when they were discharged after powering down. It was a hard learned lesson.
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How exactly do you measure the power left in the main filter caps after power-off? What's the best/safest way?
 
I apply the contacts of a voltage meter, + to + and - to -, and watch the meter. When the meter shows voltage at a reading close to 0 then you know they have discharged.I can't remember whether I had it set on AC or DC. Another way to deal with them is to attach large resistors, what resistance I can't remember, and as soon as you remove voltage, the resistors will discharge the caps. There is a good deal of info regarding this on AK.
 
onwardjames said:
Somehow I stopped getting notifications on this. Some great stories, and hard lessons learned.
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If you don't respond to a notification it drops you from the list. But the thread stays in your watched threads so you can get back on the list by becoming current in the thread ( read it from where the software puts back into the thread). Then notifications start again it seems.
 
AV-Man said:
I think I'll take the cake here...

11 years ago I threw a Sansui 9090DB in the dumpster because white smoke came out. Now to think it was probably a board or solder joint and they are selling for 3 grand!!
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How about tossing a Marantz 2235B in the trash because the pots were dirty and one channel dropped in and out? I didn’t know about deoxit at the time.
 
Here's a recent one. I acquired a Pioneer PL 12D. It was pretty rough but the plinth was perfect so I decided I could rebuild. I got everything working and decided the tonearm had too much play. So, I dismantled the tonearm to adjust the bearings. Well, the arm has two sets of about thirty very small loose ball bearings that immediately fell out on my workbench. I tried for hours to get them all back. I assume Pioneer had special tools for this. Anyway, It's in a box cause I can't stand to look at it any more.
 
dcgibby said:
Here's a recent one. I acquired a Pioneer PL 12D. It was pretty rough but the plinth was perfect so I decided I could rebuild. I got everything working and decided the tonearm had too much play. So, I dismantled the tonearm to adjust the bearings. Well, the arm has two sets of about thirty very small loose ball bearings that immediately fell out on my workbench. I tried for hours to get them all back. I assume Pioneer had special tools for this. Anyway, It's in a box cause I can't stand to look at it any more.
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I did the same to a thrift store found PL-4. The balls never fell out on me, but I still had one hell of a time getting it back together. Oh, and the play was still present after reassembly...
 
I did that on a Garrard Lab 80 once. I think its 15 or so, tiny things that look like grains of perfectly round sand. Of course when you drop them on your messy shop floor you know not all of them are coming back. Friend of mine had some that happened to be the right size from some RC car stuff he used to fool with. Not a fun job putting that back together.
 
onwardjames said:
I was reading my monthly RockAuto newsletter, and thought this might make a fun thread.

The idea is simple - please share something you did that either could have ended very badly, or DID end badly, but preferably something that you just pulled a senior moment on....here's mine!!

Got my much-desired Pickering XVS-3000 with Clearaudio Microridge stylus and boron cantilever, a one-off from a known retipper, and dialed it it.....

WOW, this sounds great........wait.....SCREEECH!!! There goes the tonearm bouncing around.

Fiddle with antiskating, recheck balance and VTF........DAMMIT.

This goes on for nearly 4 hours.

Reached out to my guy, who said he had it happily surviving a torture test record at 1 gram.

WHAT THE EFF??

Welp. Turns out I didn't factor the weight of the Pickering brush, which applies a downforce of ......you guessed it......1 gram, which was where I was trying to get it to play, even going as high as 1.5 (which would give me a net of .5 grams tracking force).

Lesson learned - gotta factor in the resistance of that brush.


What do you guys have??
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Same thing, twice. many years ago and when I dug this thing outta mothballs.....

Kevin
 
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