I am working on an old Magnatone. There are two wires from the PT that go to chassis ground. I assume one is the ground for the primary, and maybe the other is the heater CT.
Can I use a DMM to figure out what the grounds are for? If I lift the PT primary, the leads for the heater supply, and the two grounded wires, can I just do a continuity test to see which CT goes to which leads?
Thank You
Power Trans CT
Moderators: pompeiisneaks, Colossal
Re: Power Trans CT
Yes x 2hired hand wrote: Can I use a DMM to figure out what the grounds are for? If I lift the PT primary, the leads for the heater supply, and the two grounded wires, can I just do a continuity test to see which CT goes to which leads?
Thank You
Re: Power Trans CT
Wow!!tubeswell wrote:Yes x 2hired hand wrote: Can I use a DMM to figure out what the grounds are for? If I lift the PT primary, the leads for the heater supply, and the two grounded wires, can I just do a continuity test to see which CT goes to which leads?
Thank You
I finally figured something out for myself......
Thanks for the confirmation.
Re: Power Trans CT
Yeah, OK.dynaman wrote:You only need to lift the center taps.
Guess I am not as smart as I thought I was.....
Thank You
Re: Power Trans CT
OK.....the heater CT has two leads. Is that normal..?
The other CT reads about 160 ohms to Pin 4 and 6 of the rectifier. Shouldn't that be close to 1 ohm?
It might be hard to see in the picture....The heater CT has two leads, they are hanging over that loan filter cap on the left.
The high voltage CT is a thin yellow wire, stranded, and it is hanging over the fuse holder. With that reading of 160 ohms, is my PT making a good ground? I have had some issues with hum.
Thanks
The other CT reads about 160 ohms to Pin 4 and 6 of the rectifier. Shouldn't that be close to 1 ohm?
It might be hard to see in the picture....The heater CT has two leads, they are hanging over that loan filter cap on the left.
The high voltage CT is a thin yellow wire, stranded, and it is hanging over the fuse holder. With that reading of 160 ohms, is my PT making a good ground? I have had some issues with hum.
Thanks
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Re: Power Trans CT
Typically (there is no such thing as normal), leads are soldered onto the windings and then the leads are drawn out for connection to the circuit. Sometimes, the actual ends of the winding are drawn out for connection without extensions.
In the case of a center tap, what is done is that the winder makes a loop but doesn't break the winding. When an extension is soldered onto the loop, you never see the loop. If the actual loop is drawn out for connection, then it is possible someone cut the loop. If that happened, you'll have what appears to be two CT leads. You must connect (ground) both at the same spot to connect the two parts of the winding.
It is always difficult for me to judge from a picture. I think I see two leads emerging from one braided insulator. Those leads look like they have enamel on them and the enamel has been removed at the end of the "loop". In this case, the loop was cut by someone who didn't know to leave it alone or simply from use, reuse, abuse.
I'm not really clear where you are seeing 160 Ohms. I don't think you'd see that on a filament winding but you certainly could see that on the high voltage secondary.
So, treat both ends from that insulator as if they need to be connected. I think that is what you need to do.
In the case of a center tap, what is done is that the winder makes a loop but doesn't break the winding. When an extension is soldered onto the loop, you never see the loop. If the actual loop is drawn out for connection, then it is possible someone cut the loop. If that happened, you'll have what appears to be two CT leads. You must connect (ground) both at the same spot to connect the two parts of the winding.
It is always difficult for me to judge from a picture. I think I see two leads emerging from one braided insulator. Those leads look like they have enamel on them and the enamel has been removed at the end of the "loop". In this case, the loop was cut by someone who didn't know to leave it alone or simply from use, reuse, abuse.
I'm not really clear where you are seeing 160 Ohms. I don't think you'd see that on a filament winding but you certainly could see that on the high voltage secondary.
So, treat both ends from that insulator as if they need to be connected. I think that is what you need to do.
Re: Power Trans CT
Thanks Phil, that all makes sense.
Where I see 160 ohms is the high voltage AC secondary to it's CT. Is that big of a number par for the course..?
Thanks You
Where I see 160 ohms is the high voltage AC secondary to it's CT. Is that big of a number par for the course..?
Thanks You
Re: Power Trans CT
I'm far from an expert, but I have a few PT's that I've collected for some as yet unknown projects. I just checked a few of them. The HV secondary windings cover a pretty wide range. Yours at 160/half is on the high side, but not beyond what I'd guess is the relevant range. Some are quite low. I've got several that are in the 35-100 ohm range for both halves. If the PT delvers what you expect, I wouldn't pursue this question.
Re: Power Trans CT
Yeah....OK.Phil_S wrote:I'm far from an expert, but I have a few PT's that I've collected for some as yet unknown projects. I just checked a few of them. The HV secondary windings cover a pretty wide range. Yours at 160/half is on the high side, but not beyond what I'd guess is the relevant range. Some are quite low. I've got several that are in the 35-100 ohm range for both halves. If the PT delvers what you expect, I wouldn't pursue this question.
All the numbers seem fine, so no problem.
Thanks Again
Re: Power Trans CT
Wait,
In your picture, is that the rectifier tube?
You have the 6.3v heater wires going to that as well as the 5v wires?
In your picture, is that the rectifier tube?
You have the 6.3v heater wires going to that as well as the 5v wires?
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Power Trans CT
The 6 volt wire are on Pins 3 and 7....No Connection.