Me: -But after the transformer I am separated from earth, and it's less dangerous
Renron -Not only the A/C but how about the B+???
If the B+ gets in contact with my chassis the fuse will blow immideatly.
But: Let's say I made a bad connection (no contact) between ground and chassiss.
The B+ gets in contact with the chassis and I touch the amp. Still nothing happens!
A couple of minutes ago I touched my B+ just to be sure I was right. I was, cause nothing happened
I didn't feel anything!
Example:
It's dangerous to touch phase, because the current will flow through your body down to ground. Not recommended!
The neutral should not be dangerous, but don't try!
But after the transformer we are separated from earth! You can touch tap 1, or tap 2 and nothing will happen!
Do not touch both though!!! If you touch both you will of course have an electrical shock!
In other words: It should not be dangerous to touch the B+ if you use a transformer
I do not recommend anyone to try the thing I tried, but I thought I had to know the truth...
Renron -Not only the A/C but how about the B+???
If the B+ gets in contact with my chassis the fuse will blow immideatly.
But: Let's say I made a bad connection (no contact) between ground and chassiss.
The B+ gets in contact with the chassis and I touch the amp. Still nothing happens!
A couple of minutes ago I touched my B+ just to be sure I was right. I was, cause nothing happened
I didn't feel anything!Example:
An externally hosted image should be here but it was not working when we last tested it.
It's dangerous to touch phase, because the current will flow through your body down to ground. Not recommended!
The neutral should not be dangerous, but don't try!
But after the transformer we are separated from earth! You can touch tap 1, or tap 2 and nothing will happen!
Do not touch both though!!! If you touch both you will of course have an electrical shock!
In other words: It should not be dangerous to touch the B+ if you use a transformer
I do not recommend anyone to try the thing I tried, but I thought I had to know the truth...
ollebolle said:The last post was not an argument not to ground the chassis!
I totally agree with all you people saying you should ground the chassis for safety!
Grounded chassis is safe! I will do it, I promise
You are correct the B+ is NOT the same as the A/C, it's a second order insulated circuit. However if you touch the case and the B+ at the same time, you're gonna glow in the dark.
Transformers only separate the Primary from the Secondary.....
the Secondary B+ voltage is MORE dangerous than the A/C.
Merck states that 60HZ AC is "3 to 5 times more dangerous than DC of the same voltage and amperage. Low-frequency AC produces extended muscle contraction (tetany), which may freeze the hand to the current's source, prolonging exposure. DC is most likely to cause a single convulsive contraction, which often forces the victim away from the current's source."link to AC vs DC
Please don't test like this anymore. You may be safe but it may also give others ideas it would be safe for them too.
Ron
Will the placement of the tranny's have any effect on the psu and main board?
I mean if they are close to the tube and other components could there be any unwanted side effects?
I'm thinking I could build a base for the tranny's totally separate from the main board and psu to isolate them otherwise they will be very close to the circuitry.
I mean if they are close to the tube and other components could there be any unwanted side effects?
I'm thinking I could build a base for the tranny's totally separate from the main board and psu to isolate them otherwise they will be very close to the circuitry.
Brit,
Xformer placement won't have much effect on the Mobo or PSU board. Not likely to affect the rectifier tube either.
With the Xformers exposed (up top) that should be enough to mediate their flux effect on the Mobo.
If you are using a choke input on the PS board it will effect the choke dramaticly. Here's how I figured my Xformer / choke layout:
Being cautious not to short the secondaries, apply power to the primary side of both Xformers, set them approximatly where you would want them to live. Clip the leads of your Ohm meter to the choke's two wires and move it around the Xformers.....watch the meter move magicly. When you have found the location that effects the least and your happy with the look, bingo, your done.
Make sure to set Xformer windings at 90* to each other if they are close. A great explaination of this procedure can be found in "Building Valve Amplifiers" by Morgan Jones.
Very nice looking Xformers BTW.
Ron
Brit01 said:
Xformer placement won't have much effect on the Mobo or PSU board. Not likely to affect the rectifier tube either.
With the Xformers exposed (up top) that should be enough to mediate their flux effect on the Mobo.
If you are using a choke input on the PS board it will effect the choke dramaticly. Here's how I figured my Xformer / choke layout:
Being cautious not to short the secondaries, apply power to the primary side of both Xformers, set them approximatly where you would want them to live. Clip the leads of your Ohm meter to the choke's two wires and move it around the Xformers.....watch the meter move magicly. When you have found the location that effects the least and your happy with the look, bingo, your done.
Make sure to set Xformer windings at 90* to each other if they are close. A great explaination of this procedure can be found in "Building Valve Amplifiers" by Morgan Jones.
Very nice looking Xformers BTW.
Ron
Today I have been working on the hum problem.
There is most hum in my right channel, and much less in left!
First I removed my old heater-wires, and made new better ones using a proper method. Always follow corners, and far away from the components...
The hum didn't change.
I tried DC-heaters. I have a 13,5V stabilised power supply.
I made a voltage divider between the heaters and some power resistors, and calculated the value of the resistors using Ohm:s law.
My voltmeter measured 6,6 VDC over the heaters, and I thought it was close enough just for a short test.
The hum still didn't change.
Then I made woodturner-fran:s ground breaker circuit.
Didn't help either, but it might be good anyway...
So I switched places of the tubes, just to make sure the tubes are ok.
No change, so I think they are good.
Then I connected my oscilloscope on the output:
Left channel:
Right channel:
The input is my Squeezebox music-player and it was paused, so this is only the hum, no other signal!
I have a triangle-shaped waveform on the output
This is very strange!
I have no idea why this is happening, but I will take a look at the power supply tomorrow.
There is most hum in my right channel, and much less in left!
First I removed my old heater-wires, and made new better ones using a proper method. Always follow corners, and far away from the components...
The hum didn't change.
I tried DC-heaters. I have a 13,5V stabilised power supply.
I made a voltage divider between the heaters and some power resistors, and calculated the value of the resistors using Ohm:s law.
My voltmeter measured 6,6 VDC over the heaters, and I thought it was close enough just for a short test.
The hum still didn't change.
Then I made woodturner-fran:s ground breaker circuit.
Didn't help either, but it might be good anyway...
So I switched places of the tubes, just to make sure the tubes are ok.
No change, so I think they are good.
Then I connected my oscilloscope on the output:
Left channel:
An externally hosted image should be here but it was not working when we last tested it.
Right channel:
An externally hosted image should be here but it was not working when we last tested it.
The input is my Squeezebox music-player and it was paused, so this is only the hum, no other signal!
I have a triangle-shaped waveform on the output
This is very strange! I have no idea why this is happening, but I will take a look at the power supply tomorrow.
Interesting find Olle. Maybe a faulty component on that channel. Very strange. Let me know what you discover.
I'm still trying to figure out what I need to do with the heater bias point on Bas's psu. In cases I've seen they have attached the CT to this but I have no center tap on my tranny's.
Also what do I use as a ground point if I am not using a metal chassis? Just a thick copper rod maybe?
I'm still trying to figure out what I need to do with the heater bias point on Bas's psu. In cases I've seen they have attached the CT to this but I have no center tap on my tranny's.
Also what do I use as a ground point if I am not using a metal chassis? Just a thick copper rod maybe?
About the grounding: This is a good method!
A copper bar will work fine!
An externally hosted image should be here but it was not working when we last tested it.
A copper bar will work fine!
Hummm elimination
Stixx wrote:
I too have some hum on a combined phono & line preamp I built. The hum is coming from the phono section, because it's not there from the line preamp. I tried a number of modifications but it's still there.
I was wondering what you mean by: "I had connected the shield of the input wires on both sides." Isn't this how it should be?
In my system I have separate earths for each channel. The shield of the input wires (from the input jacks) goes to the corresponding channel earth point. The two earth points are then connected together and wired to a common earth point.
Could this be what is causing the hum in my system. I know I could try it out and see but there's no harm in asking first.
Regards,
Joe A
Stixx wrote:
I too have some hum on a combined phono & line preamp I built. The hum is coming from the phono section, because it's not there from the line preamp. I tried a number of modifications but it's still there.
I was wondering what you mean by: "I had connected the shield of the input wires on both sides." Isn't this how it should be?
In my system I have separate earths for each channel. The shield of the input wires (from the input jacks) goes to the corresponding channel earth point. The two earth points are then connected together and wired to a common earth point.
Could this be what is causing the hum in my system. I know I could try it out and see but there's no harm in asking first.
Regards,
Joe A
Quote:
I'm still trying to figure out what I need to do with the heater bias point on Bas's psu. In cases I've seen they have attached the CT to this but I have no center tap on my tranny's.
No center tap on your heater supply? No problem ...attach a 100 ohm resistor to each leg. attach the ends of the resistors together and inject your 1/4 of the power supply there. Instant CT and a place to raise your heater supply and poof no more noise.
I had the same problem with the 2) transformers I used on my dual mono Aikido. One minute I had noise and the next it was gone.
Go thru your grounding. I used microphone wire on the input jacks to the boards and also to the 2) VC's I have.
I'm still trying to figure out what I need to do with the heater bias point on Bas's psu. In cases I've seen they have attached the CT to this but I have no center tap on my tranny's.
No center tap on your heater supply? No problem ...attach a 100 ohm resistor to each leg. attach the ends of the resistors together and inject your 1/4 of the power supply there. Instant CT and a place to raise your heater supply and poof no more noise.
I had the same problem with the 2) transformers I used on my dual mono Aikido. One minute I had noise and the next it was gone.
Go thru your grounding. I used microphone wire on the input jacks to the boards and also to the 2) VC's I have.
"I had connected the shield of the input wires on both sides." Isn't this how it should be?
No! You should only connect one side of the shield!
Brit01: This is a way to lock the heaters if you don't have a centre-tap!
No! You should only connect one side of the shield!
Brit01: This is a way to lock the heaters if you don't have a centre-tap!
An externally hosted image should be here but it was not working when we last tested it.
Thks for that.
So if I understand correctly, also trying to visualize my JB Aikido board and Bas's psu,
I would connect the Hot and Neutral cables from the secondary with 2 resistors and ground the mid point?
Sounds a bit dangerous.
What would happen if I just connect the + and - cables from the secondary to the board without a center tap or this mod?
Thks
So if I understand correctly, also trying to visualize my JB Aikido board and Bas's psu,
I would connect the Hot and Neutral cables from the secondary with 2 resistors and ground the mid point?
Sounds a bit dangerous.
What would happen if I just connect the + and - cables from the secondary to the board without a center tap or this mod?
Thks