UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - G & E Bradley CT-471

Sinewave · 20th Nov 2018, 10:49 pm

Some more tests tonight from paragraph 5.6.3.

Chopper circuit test. Short the junction of R79 and R80. I couldn't find R80, so I shorted the R79 and was able to get movement using RV11 to take the scale away from zero and back to zero.

Checking the chopper waveform shows a squarewave with a sharp spike to the + peak which then slopes down to 0. Peak to peak is 4.72v, where it should be 2v.

So I need to find out why.

20th Nov 2018, 10:49 pm	#83
Sinewave Octode Join Date: May 2016 Location: Oxfordshire/Bucks borders, UK. Posts: 1,604	Re: G & E Bradley CT-471 Some more tests tonight from paragraph 5.6.3. Chopper circuit test. Short the junction of R79 and R80. I couldn't find R80, so I shorted the R79 and was able to get movement using RV11 to take the scale away from zero and back to zero. Checking the chopper waveform shows a squarewave with a sharp spike to the + peak which then slopes down to 0. Peak to peak is 4.72v, where it should be 2v. So I need to find out why. Attached Thumbnails __________________ Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.