Safety Practices, General and Ultra-High Voltage - Page 45

opcom · 05:34 AM

@ AllIsParadox:

I live too much in the past with those wireless video links and stuff.. - a smartphone with the facetime-like app or something would also be a way, if minutes are not an issue.

6A3sUMMER · 10th May 2020, 06:17 AM

opcom,

The only 110VDC gear I ever saw was my brothers Philco AM 4 tube radio with 3-way power
(90VDC battery + 1.5V or 3V battery; 110VAC; and 110VDC).

Parallel resistors for a bleeder is a pretty good idea.
The problem with bleeder resistors is that you can get carried away.
Suppose you have an amplifier B+ filter that is CRCRCRC.
Which C do you put the parallel bleeder resistors across?
What if one of the 3 Rs in that B+ filter burns out, then one end or the other of that filter chain will not be bled down.
So you use 8 bleeder resistors just to be safe?

I use resistors that have power ratings of 5X the power that will be in them. They run cooler, and are less likely to fail.

jy999 · 3rd September 2020, 12:41 AM

I'm a long-term electronics hobbyist getting started on tube amps. Boy this thread is giving me anxiety - this is terrifying! Good info, though. I'd rather be scared, and careful, than injured or dead.

I just picked up a 15w amp with a dead transformer (apparently). Waiting for my variac and parts to build a bulb limiter and capacitor draining leads, and then I'll pull and test that transformer. Wish me luck!

jwags818 · 13th January 2021, 09:35 PM

I can attest 500+V hurts! Being one of the few that don't seem to learn very fast I have hit myself good 3 times with 500V+. Once thru both hands. Luckily didn't do a thing to me but hurt. I did however blow a hole in my arm once and bled all over the place. From a shock..!!
Bleed resistors save lives.... Use them.

10th May 2020, 05:30 AM	#441
opcom diyAudio Member Join Date: May 2008 Location: Texas	@ AllIsParadox: I live too much in the past with those wireless video links and stuff.. - a smartphone with the facetime-like app or something would also be a way, if minutes are not an issue. Last edited by opcom; 10th May 2020 at 05:34 AM.

13th January 2021, 09:35 PM	#444
jwags818 diyAudio Member Join Date: Aug 2005 Location: Wilsonville Oregon, Corvallis Oregon native (You can't lick our beavers!).	I can attest 500+V hurts! Being one of the few that don't seem to learn very fast I have hit myself good 3 times with 500V+. Once thru both hands. Luckily didn't do a thing to me but hurt. I did however blow a hole in my arm once and bled all over the place. From a shock..!! Bleed resistors save lives.... Use them. __________________ Jwags818 - Wilsonville, Oregon D50s - 300B/D3A SET - 12in Audio Nirvana Speakers

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10th May 2020, 06:17 AM	#442
6A3sUMMER diyAudio Member Join Date: Jun 2016	opcom, The only 110VDC gear I ever saw was my brothers Philco AM 4 tube radio with 3-way power (90VDC battery + 1.5V or 3V battery; 110VAC; and 110VDC). Parallel resistors for a bleeder is a pretty good idea. The problem with bleeder resistors is that you can get carried away. Suppose you have an amplifier B+ filter that is CRCRCRC. Which C do you put the parallel bleeder resistors across? What if one of the 3 Rs in that B+ filter burns out, then one end or the other of that filter chain will not be bled down. So you use 8 bleeder resistors just to be safe? I use resistors that have power ratings of 5X the power that will be in them. They run cooler, and are less likely to fail.

3rd September 2020, 12:41 AM	#443
jy999 diyAudio Member Join Date: Sep 2020	I'm a long-term electronics hobbyist getting started on tube amps. Boy this thread is giving me anxiety - this is terrifying! Good info, though. I'd rather be scared, and careful, than injured or dead. I just picked up a 15w amp with a dead transformer (apparently). Waiting for my variac and parts to build a bulb limiter and capacitor draining leads, and then I'll pull and test that transformer. Wish me luck!