Genrad 1656 impedence bridge

chanwoo · 18th March 2010, 11:34 AM

Gentlemen,

Recently I bought old and used Genrad 1656 inpedence bridge and looking not bad. But I can't utilize it as my wishes. Is anybody knows how to use it well? I'm specially want to check transformer's impedence with it.

I could measure resistors and capacitors however it is reading wrong value in case 150uF like as 100uF. And I even can't control it because meter reading doesn't over rap null(midedle). when I'm measuring impedence. I read manual but difficult to understand.

I connected capacitor/transformer between high and low connectors with cable.

Please advise me.

Thank you in advance.

Conrad Hoffman · 21st March 2010, 04:03 AM

The GR 1656 is a pretty conventional bridge, similar to the 2-dial models, but it uses a bank of levers instead of one of the knobs. I do not believe the lever assembly is repairable, very unusual for GR equipment. As long as the switches operated by the levers are not too noisy, it should be quite serviceable. If the switches are noisy, it will be very annoying to balance. In all honesty, it's not a model I recommend.

It works like other bridges- you can measure R, L or C, along with the Q or dissipation factor. I'd start with some known components, maybe some 5% film capacitors, and learn to balance the bridge. Electrolytics will have a wide tolerance, so it's hard to tell much about the bridge with those. Use 1% resistors and film caps to start with.

To measure a transformer, you'll be measuring inductance. Try to find a speaker inductor of a known value to practice with. If you can't get the bridge to balance sharply with known components, and get the correct value, it probably needs some service.

Best,
Conrad

chanwoo · 22nd March 2010, 03:19 AM

I probably have to play with it for a while. I don't have service center near by because I'm living in Korea. And I will start with your suggestion.

Thank you for your input.

Conrad Hoffman · 23rd March 2010, 11:45 AM

Don't forget that there's a wonderful GR group at Yahoo that's moderated by Henry Hall, who designed many of the classic GR bridges:

General Radio/Genrad Group

Best,
Conrad

18th March 2010, 11:34 AM	#1
chanwoo diyAudio Member Join Date: Mar 2006 Location: Seoul	Genrad 1656 impedence bridge Gentlemen, Recently I bought old and used Genrad 1656 inpedence bridge and looking not bad. But I can't utilize it as my wishes. Is anybody knows how to use it well? I'm specially want to check transformer's impedence with it. I could measure resistors and capacitors however it is reading wrong value in case 150uF like as 100uF. And I even can't control it because meter reading doesn't over rap null(midedle). when I'm measuring impedence. I read manual but difficult to understand. I connected capacitor/transformer between high and low connectors with cable. Please advise me. Thank you in advance.

21st March 2010, 04:03 AM	#2
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	The GR 1656 is a pretty conventional bridge, similar to the 2-dial models, but it uses a bank of levers instead of one of the knobs. I do not believe the lever assembly is repairable, very unusual for GR equipment. As long as the switches operated by the levers are not too noisy, it should be quite serviceable. If the switches are noisy, it will be very annoying to balance. In all honesty, it's not a model I recommend. It works like other bridges- you can measure R, L or C, along with the Q or dissipation factor. I'd start with some known components, maybe some 5% film capacitors, and learn to balance the bridge. Electrolytics will have a wide tolerance, so it's hard to tell much about the bridge with those. Use 1% resistors and film caps to start with. To measure a transformer, you'll be measuring inductance. Try to find a speaker inductor of a known value to practice with. If you can't get the bridge to balance sharply with known components, and get the correct value, it probably needs some service. Best, Conrad __________________ I used to be an audiophool like you but then I took an arrow to the knee.

23rd March 2010, 11:45 AM	#4
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	Don't forget that there's a wonderful GR group at Yahoo that's moderated by Henry Hall, who designed many of the classic GR bridges: General Radio/Genrad Group Best, Conrad __________________ I used to be an audiophool like you but then I took an arrow to the knee.

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22nd March 2010, 03:19 AM	#3
chanwoo diyAudio Member Join Date: Mar 2006 Location: Seoul	I probably have to play with it for a while. I don't have service center near by because I'm living in Korea. And I will start with your suggestion. Thank you for your input.

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