[doggie]

I have had several experiences with my own equipment and one with a friend's that resulted in either an explosion(small), smoke, and\or burning. I have been doing DIY for about 35 years and have never had a serious fire but have received a couple of bad shocks. I thought that I would start a thread regarding tube equipment and DIY to see if others have cautionary tales to tell.

I will go first.

Shocks: In the early days of building tube amps and modifying them I had two episodes that gave me a profound respect for high voltage. Once I was working on the underside of an FM receiver that was powered on and my tool slipped causing a short. That event kicked me out of my chair and the chassis dropped to the floor, luckily not on me. Another time I just spaced out and touched a bare 400 volt wire. That put a hole in my finger. In the last 30 years I have been more cautious.

I once had a Dynaco MkIII resistor burn up. Luckily I heard a pop and turned around to see it burning so that I could turn it off. Another time I had built a small Tripath amp which was battery powered. In the process of plugging in a switchable battery charger into the cheap rear panel socket I bent the center pin against the ground sleeve. The battery saw a dead short and poured its heart out melting the internal wiring and filling the room with acrid smoke. The amp and battery were OK but the house smelled pretty bad. In the case of my friend, her 2A3 amp had a solid state heater rectifier which decided to die. This short overheated the power transformer pretty much melting it. It was replaced and a smaller value fuse installed as the original one never popped

Take home lessons:

1. Never leave tube equipment on when you are not home or nearby.
2. Always use fuses of the correct value and definitely use one.
3. When testing voltages, especially in tight spaces use probes with clips/hooks. Keep one had in your pocket.
4. Always over specify DIY parts. Don't use old capacitors. When they blow it can be pretty exciting.
5. Always check power wiring multiple times when connecting it up.

Let's share our disaster stories. It could save a life or a home...




 

[tull skull]

Great idea doggie. I only have one, and minor at that but while checking voltage on a phono pre, i was momentarily distracted by something next to the test point and when i returned attention to what i was doing, the probe had moved and was politely sparking on a thankfully low voltage part of the wiring. Still could have been lethal and therefore shocked me into making sure that all actions and intentions are filtered to single tasks and then get out of there asap.

[gab]

agree with #1-5

Left hand in left pocket if right handed, reverse if left handed.

gab

[FullRangeMan]

1) 30VDC is enough to stop your heart.
2) Rubber gloves.
3) Rubber sole shoes.
4) Use new hard wiring, dont use used or computer wiring.
5) Do not wear rings or watch.
6) Do not make tests or adjustments alone.
7) Have a capable person watching your movements.
8- Cut or tie your hair.

[Johnny2Bad]

Have a well marked, safe to operate master AC switch in an easy to access area of your workbench; this should be located in such a way that it could be easily and quickly accessed by someone WITHOUT touching you or placing your body between the other person and this switch. To turn off the AC power, obviously, to the entire bench.

All persons normally expected to be on premises while you work on the bench should be drilled to know how to turn the bench AC power off and to know not to touch you or conductive surfaces prior to cutting AC power. It is also highly recommended, for many reasons, that people in your household are trained in CPR, ideally a certified course but if not, trained by someone who is certified.

There are different ways to look at safety, one being prevention. But there is another way, which is "accidents are inevitable". Know the first but expect the second. The above follows the second way; it's critical that the best outcome is the result of any accidental shock hazard.

[JohnR]

1. Never leave tube equipment on when you are not home or nearby.
2. Always use fuses of the correct value and definitely use one.
3. When testing voltages, especially in tight spaces use probes with clips/hooks. Keep one had in your pocket.
4. Always over specify DIY parts. Don't use old capacitors. When they blow it can be pretty exciting.
5. Always check power wiring multiple times when connecting it up.

6. Buy a variac.

[Wind Chaser]

Interesting topic but I suspect most people would be too embarrassed to admit their DIY disasters. 

I’m not much of a DIYer but about 40 years ago, I thought I’d do my dad a favour by spreading some fertilizer on our yellow lawn. It was pouring rain complete with thunder and lightening. I was just about to head back to school when I thought, hey there’s still enough time for me to take care the yellow lawn. I’ll quickly put some fertilizer on it and it will turn nice and green. 

So I took the spreader out of the garage and filled it up with several lbs of fertilizer, not realizing the choke was wide open. Even though I was quite young (about 12/13) I knew that too much fertilizer would burn the lawn, and there was a big pile of it on the grass under the spreader. So I closed the choke and reached for a shovel and gathered up as much as I could off the lawn. Now this worked fine for removing the better part of it but there was still too much fertilizer concentrated in a small area.

I was completely drenched and I didn’t want to be late for school, so in my desperation without really thinking it through, I took the shop vacuum out of the garage, plugged it in and started vacuuming the lawn when a bright flash of lightning followed by a loud thunder clap brought home the absurdity of what I was doing. Things weren’t going so well with the vacuum as it didn’t seem to be able to pick up much of the fertilizer. I felt defeated and now time was of the essence and I had to hurry back to school.

Still plugged in and running I brought the vacuum into the garage. I was kind of amazed to find myself in this situation, standing there in the garage soaking wet with a vacuum plugged in and powered on. For a moment I debated how am I going to deal with this. I thought about pulling the cord out of the socket real quick when it occurred to me maybe I should be standing on a rubber mat to be safe.

We had a small thick rubber mat at the entrance to the garage so I stood on it and kicked the switch with my right foot while the vacuum rested on the concrete floor. In that instant my foot felt like it had bonded to the vacuum and there was no way I could retract my foot from it. I felt the electrical current travel up my leg while I screamed balancing on the other foot with the rubber mat underneath. As the motor winded down the current up my leg lessened and I was finally able to release my foot from the vacuum. I thought, fuck I’ll never do that again. 

[modwright]

Thanks for sharing!  That is both horrifying and hilarious! We have all been in some sort of similar situation.  The thing is, you really had your wits about you and actually thought about it before you tried to turn it off.  I can only assume that the mat was wet and still grounded you. I am glad you are OK!

As a tube designer and working with high voltages for some time now, I have had my share of 'zaps'.  Fortunately, really nothing worse than about 500VDC and 240VAC. The most painful is probably when a power supply is unplugged, but still holding a charge at 400VDC+.  Both hands in the unit of course, the supply discharges across your chest and heart.  As I recall, it was accompanied by a kind of UMF! sound, followed by a few choice expletives, as the supply bounced on the floor. In the early days, working in my basement, my wife and I agreed that I would always follow such commotion with "I'm OK!".

I have designed an 845 amp that runs at 1200V. When working on this design, I ALWAYS had both feet off the floor and ONLY one hand at a time inside the amp.  I RESPECTED the 1200V!  I knew enough, as my father worked as a nuclear radar tech in the early 60's for the Navy.  He told me stories of working on tube transmitter gear, obviously at very high voltages.

At one time he told me that he was working with a junior tech.  He had to reach inside of a dangerous piece of gear.  He told the junior tech that if he slipped and fell, go find someone and tell them.  No hurry, just let them know, as there would be nothing to be done to help him at that point.

Bottom line, respect electrons!

Thanks for sharing!

Dan Wright