UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Heathkit V-7AUK VTVM 12AU7 substitute

Chris55000 · 2nd Aug 2020, 11:42 am

Hi!

You also need to make sure the meter movement magnet hasn't lost any of it's magnetic field strength – to test for this, connect a 10k resistor in series with a fresh 1.5V AA battery to the Meter's (+) and (–) terminals with the PCB removed from the back – if the movement is sensitive enough for the circuit, the pointer should deflect ⅔ of the way–upscale, if the deflection is much less than this, the meter movement will need re–magnetising – other members who have more experience with movement problems than me can best advise on this point!

The normal f.s.d. sensitivity of the Heathkit Movements is 200uA nominal!

Chris Williams

2nd Aug 2020, 11:42 am	#8
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Re: Heathkit V-7AUK VTVM 12AU7 substitute Hi! You also need to make sure the meter movement magnet hasn't lost any of it's magnetic field strength – to test for this, connect a 10k resistor in series with a fresh 1.5V AA battery to the Meter's (+) and (–) terminals with the PCB removed from the back – if the movement is sensitive enough for the circuit, the pointer should deflect ⅔ of the way–upscale, if the deflection is much less than this, the meter movement will need re–magnetising – other members who have more experience with movement problems than me can best advise on this point! The normal f.s.d. sensitivity of the Heathkit Movements is 200uA nominal! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!