[AMRadio] tranny
Does anyone happen to have a 5 volt @ 20 amp tranny lying around they'd like to sell? It needs to have a insulation voltage of at least 5000 volts and 10,000 would be best. The HV filament transformer in the GE gave it up today and until I can get it rewound I am in need of a temporary replacement for testing purposes. Thanks, Rick/K5IAR __ AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Tranny Test
Okay.. I have decided the filament transformer in the GE may still be okay. I've had it connected through a Variac at 100 volts (the stated primary voltage of the transformer) for about 2 hours and it is barely warm. I also have a 5R4 filament connected to it as it would be in the circuit. In addition to that I have about 10 ohms of resistance on the output causing a current draw of about 450 ma. With all of this it still seems to be fine and is not heating up at all. However, I need a way to test the high voltage insulating properties of the secondary since this is used in a full wave rectifier circuit of about 800 volts. I do not have a megger or similar device, so is there any quick and easy test I can perform short of putting it back into the actual circuit to see if it breaks down under full load conditions? Rick/K5IZ __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Tranny Test
Re: quasi-pseudo hi-pot testing of your transformer - if you have a device that produces the required 800-1000 VDC - and can access that voltage (such as a bench supply, one of the other power supplies in the transmitter - or even a Ranger maybe) then [carefully!] attach the positive lead of that source to the windings (tie the leads toggether) thru a suitable microammeter and ground the tranny frame... any leakage will show up on the microammeter. A panel-mount 0-20 uA DC meter, mounted on a piece of plastic, will do. If you use a DVM - just insulate it well - put it in series - don't let any part of it get near ground or you - set the meter, step back - turn on the HV - check the reading. Shouldn't be very many microamps to ground. Note that any significant ripple, or other AC disturbances, in the HV source, will confuse the reading, due to capacitive and inductive coupling of those components. Use 'pure' DC. Remember to tie the transformer HV leads together - the object is to measure any current flow from the body of the windings, thru the insulation, to the frame - NOT from one side of the winding to the other - which would only be a few ohms DC resistance. Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Tranny Test
Bingo! That should tell me exactly what I need to know. Thanks, John! Rick John Lawson wrote: Re: quasi-pseudo hi-pot testing of your transformer - if you have a device that produces the required 800-1000 VDC - and can access that voltage (such as a bench supply, one of the other power supplies in the transmitter - or even a Ranger maybe) then [carefully!] attach the positive lead of that source to the windings (tie the leads toggether) thru a suitable microammeter and ground the tranny frame... any leakage will show up on the microammeter. A panel-mount 0-20 uA DC meter, mounted on a piece of plastic, will do. If you use a DVM - just insulate it well - put it in series - don't let any part of it get near ground or you - set the meter, step back - turn on the HV - check the reading. Shouldn't be very many microamps to ground. Note that any significant ripple, or other AC disturbances, in the HV source, will confuse the reading, due to capacitive and inductive coupling of those components. Use 'pure' DC. Remember to tie the transformer HV leads together - the object is to measure any current flow from the body of the windings, thru the insulation, to the frame - NOT from one side of the winding to the other - which would only be a few ohms DC resistance. Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Tranny Test
You had best have something to protect that microameter when you turn on the supply as the capacitance of the transformer windings will look like a short to the meter until the charge equalizes. Running it up with a variac would be ok. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of John Lawson Sent: Monday, February 19, 2007 3:38 PM To: Discussion of AM Radio in the Amateur Service Subject: Re: [AMRadio] Tranny Test Re: quasi-pseudo hi-pot testing of your transformer - if you have a device that produces the required 800-1000 VDC - and can access that voltage (such as a bench supply, one of the other power supplies in the transmitter - or even a Ranger maybe) then [carefully!] attach the positive lead of that source to the windings (tie the leads toggether) thru a suitable microammeter and ground the tranny frame... any leakage will show up on the microammeter. A panel-mount 0-20 uA DC meter, mounted on a piece of plastic, will do. If you use a DVM - just insulate it well - put it in series - don't let any part of it get near ground or you - set the meter, step back - turn on the HV - check the reading. Shouldn't be very many microamps to ground. Note that any significant ripple, or other AC disturbances, in the HV source, will confuse the reading, due to capacitive and inductive coupling of those components. Use 'pure' DC. Remember to tie the transformer HV leads together - the object is to measure any current flow from the body of the windings, thru the insulation, to the frame - NOT from one side of the winding to the other - which would only be a few ohms DC resistance. Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Tranny Test Afterthought
One think I just thunked is: I don't know if you have any really small-current fuses, like 100mA or so - if you do, perhaps you could put one in series with the meter - if there is a substantial internal short, or even an accidental flashover - it's bound to kill the meter... don't want that to happen. Most DVMs are fused internally, so that's safer, I think. But hey - what's electronic RD without the occasional fireworks display? Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Tranny Test
On Mon, 19 Feb 2007, Gary Schafer wrote: You had best have something to protect that microameter when you turn on the supply as the capacitance of the transformer windings will look like a short to the meter until the charge equalizes. Running it up with a variac would be ok. Yeah - and the inductive kick too - I forgot about that. Maybe a 50 or 100K resistor in the circuit to snub all that inrush-type stuff...? Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Tranny Test Afterthought
Ya just gotta let the smoke out every now and then to be sure the legend is true! Thanks, you're right.. Rick John Lawson wrote: One think I just thunked is: I don't know if you have any really small-current fuses, like 100mA or so - if you do, perhaps you could put one in series with the meter - if there is a substantial internal short, or even an accidental flashover - it's bound to kill the meter... don't want that to happen. Most DVMs are fused internally, so that's safer, I think. But hey - what's electronic RD without the occasional fireworks display? Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
