Power Supply Fault - TubeMic

[Shawnobi]

I just can't get over the fact that it will run for over 10 years With a cheap 16v cap. Then I replace with an arguably better quality 16v cap and that blows in minutes. Feels fishy. 25v cap's in the post though.

 

[CJ]

What brand cap?

 

[Goblin]

Why would you do that ? It's dangerous and you are more likely to get a bad shock.

Will look into that. Thanks for correcting the mistake.

So to be sure, it's better to not ground oneself when working with 120/230V? I guess it's just due to the nature of this one project.

One hand behind your back is a must as far as I know. Or that one is scrapped as well?

 

[Rob Flinn]

Will look into that. Thanks for correcting the mistake.

So to be sure, it's better to not ground oneself when working with 120/230V? I guess it's just due to the nature of this one project.

One hand behind your back is a must as far as I know. Or that one is scrapped as well?

If you ground yourself & you do touch something live then you will have created a very good path for that electricity to travel through your body to.

Locally to me there was a man who was a HAM radio guy who owned an electronics surplus store & was very experienced. He was leaning on a transmitter case with his chest when he got a shock. It was game over for him.

It is particularly bad if you have one hand grounded & the shock is to the other hand. That way the current passes through your heart. If you are probing live you should only use one hand & it is good practise to sit on the other one to stop yourself accidently grounding yourself. That way the current doesn't have a great path to flow through your body. I normally wear those tactile cotton gloves with the rubber dipping on the palms & fingers. They may not be perfect insulators, but it's better than nothing & they kind of remind me to be careful.

 

[Tubetec]

Ok , lets say we go with grounding like you said , now if we recieve a shock it could easily pass across the chest and stop the heart , if we stay seperate from ground , insulated on floor boards with rubber soles on your shoes only a very small leakage current could pass through us ,which most likely wouldnt be lethal . Never ever touch the chassis of a tube amp with one hand while probing with the other . Direct mains power is far more dangerous due to the very low source impedence .

I think you probably need to modify your original post Goblin .

 

[Tubetec]

Thats a scarey story you told Rob , just goes to show even people with vast experience and should have known better can get caught on the hop too .

 

[Goblin]

Locally to me there was a man who was a HAM radio guy who owned an electronics surplus store & was very experienced. He was leaning on a transmitter case with his chest when he got a shock. It was game over for him.

It is particularly bad if you have one hand grounded & the shock is to the other hand. That way the current passes through your heart. If you are probing live you should only use one hand & it is good practise to sit on the other one to stop yourself accidently grounding yourself. That way the current doesn't have a great path to flow through your body. I normally wear those tactile cotton gloves with the rubber dipping on the palms & fingers. They may not be perfect insulators, but it's better than nothing & they kind of remind me to be careful

Thanks for explainig Rob.

"& it is good practise to sit on the other one to stop yourself accidently grounding yourself."

I'll do this as well when working from now on, apart from keping one hand in my pocket, I'll switch em' up to stay comfortable. Safety is very important.

I already understood, but when I see people working on amp heads, and on PC's, like in YT videos (not actually YouTubers, but technichians that happen to upload videos to YT), I see a lot of them "grounding" themselves, that is, using the wrist band that attaches to the metal body which is been working upon. I know this is 101 and super basic for most of you, I'm learning. What is the "reasoning" when people do this if it is potentially risky? Worse than not wearing one?

I only expand on this subject bc I think safety is very important.

 

[Goblin]

Ok , lets say we go with grounding like you said , now if we recieve a shock it could easily pass across the chest and stop the heart , if we stay seperate from ground , insulated on floor boards with rubber soles on your shoes only a very small leakage current could pass through us ,which most likely wouldnt be lethal . Never ever touch the chassis of a tube amp with one hand while probing with the other . Direct mains power is far more dangerous due to the very low source impedence .

I think you probably need to modify your original post Goblin .

Thanks for the explanation. Corrected.

 

[Goblin]

Sometimes (most of the time) I place my non-working hand inside my pocket. Is less uncomfortable than keeping it hanging and I tend to not move it from there due to that, just sits comfortably there, and if I unconsciously try to take it out of my pocket, I'm quickly reminded to keep it there, safe, or to take a break from working on a potential high risk project (at least for me, I'm learning). Thirty minutes or so offa break, then back to work.

I have't wored those bracelets, but is for not having the means to make one/buy one. I wear rubber soles, place other insulators, and I'm very attent. I'm very glad you guys cleared that up for me.

 

[Shawnobi]

The wrist bands you see people wear are for static electricity to protect components. They are in no way intended to be any type of personal safety.

 

[Rob Flinn]

I already understood, but when I see people working on amp heads, and on PC's, like in YT videos (not actually YouTubers, but technichians that happen to upload videos to YT), I see a lot of them "grounding" themselves, that is, using the wrist band that attaches to the metal body which is been working upon. I know this is 101 and super basic for most of you, I'm learning. What is the "reasoning" when people do this if it is potentially risky? Worse than not wearing one?

They do this because in pc's they are dealing with static sensitive deivices which are damaged easily. They shouldn't be doing this with the device switched on. As Shawnobi say this is to protect the devices not the person. So you're taking what they're doing out of context.

 

[Tubetec]

Those anti static straps provide a relatively high resistance connection to ground , I think it has a 1M resistor .
Agreed as well these are not about personal safety, it is about not damaging static sensitive devices .

 

[Shawnobi]

What brand cap?

Replaced the Chinese cap with a Japanese Sanyo.

 

[Goblin]

Thanks for the explanations. I'm guessing the person who was using it on a guitar amp head is either a false memory of mine or someone who really knows what he's doing, or one who doesn't know at all.

I probably have gotten misinformation on those wristbands as well.

If I come across that video (if it exists as explained earlier) while browsing and watching my faves, I'll post it on a new post.

 

[Shawnobi]

So, update time.

25V rated cap seems to sit happy. I'm still a bit in disbelief that that is what it was. Loaded voltage is 13V so if it is powered up with a mic attached then it's prob going to be ok compared to 15.6V unloaded. And I guess the replacement cap I put in couldn't even maintain it's own 16V rating....

Anyway, thanks for all of the help getting this solved.