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Hello there all ;
A friend brought over a vintage DIY amplifier that he purchased with a "bad" Power Transformer . He had a schematic as it was built from a magazine article and had previously heard it playing a year before.
Making resistance checks, I unsoldering some wires and found that the primary of the PT read at 2.7 Ohms ! Wow ! that's close to a dead short ! Should be around 15-25 Ohms I'm thinking. (Got to be the problem right ?)
Testing the HV secondaries I found them to be 2.1 Ohms across both ends !(around 1 Ohm from each end to the CT) Should that not read somewhere around the 500-ish Ohms area?! (this is supposed to supply 400V each side of the CT !)
I found the filament windings and they measured 2.6 Ohms ?! Isn't that high ?!
Did this transformer implode? I have never seen this before.
This is a Thorndarson 22R35, very popular but I have not been able to find winding resistance specs. Maybe I'm losing my marbles.
Wondering if this is not the original PT?
Any thoughts or advice greatly appreciated....
Rick
[font=Arial, Arial, Helvetica]You can also test a power transformer by measuring the resistance between leads. A healthy Hammond 270AX 240-0-240v power transformer measured: 14 ohms between primary leads, 223 ohms between the secondary center tap and HT wire 1 and 250 ohms from center tap to HT wire 2, 0.3 ohms between the 6.3v leads [/font]
[font=Arial, Arial, Helvetica]You can also test a power transformer by measuring the resistance between leads. A healthy Hammond 270AX 240-0-240v power transformer measured: 14 ohms between primary leads, 223 ohms between the secondary center tap and HT wire 1 and 250 ohms from center tap to HT wire 2, 0.3 ohms between the 6.3v leads [/font]
A friend brought over a vintage DIY amplifier that he purchased with a "bad" Power Transformer . He had a schematic as it was built from a magazine article and had previously heard it playing a year before.
Making resistance checks, I unsoldering some wires and found that the primary of the PT read at 2.7 Ohms ! Wow ! that's close to a dead short ! Should be around 15-25 Ohms I'm thinking. (Got to be the problem right ?)
Testing the HV secondaries I found them to be 2.1 Ohms across both ends !(around 1 Ohm from each end to the CT) Should that not read somewhere around the 500-ish Ohms area?! (this is supposed to supply 400V each side of the CT !)
I found the filament windings and they measured 2.6 Ohms ?! Isn't that high ?!
Did this transformer implode? I have never seen this before.
This is a Thorndarson 22R35, very popular but I have not been able to find winding resistance specs. Maybe I'm losing my marbles.
Wondering if this is not the original PT?
Any thoughts or advice greatly appreciated....
Rick
[font=Arial, Arial, Helvetica]You can also test a power transformer by measuring the resistance between leads. A healthy Hammond 270AX 240-0-240v power transformer measured: 14 ohms between primary leads, 223 ohms between the secondary center tap and HT wire 1 and 250 ohms from center tap to HT wire 2, 0.3 ohms between the 6.3v leads [/font]
[font=Arial, Arial, Helvetica]You can also test a power transformer by measuring the resistance between leads. A healthy Hammond 270AX 240-0-240v power transformer measured: 14 ohms between primary leads, 223 ohms between the secondary center tap and HT wire 1 and 250 ohms from center tap to HT wire 2, 0.3 ohms between the 6.3v leads [/font]
