UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Microvitec Cub 1431 Power but no picture.

SiriusHardware · 5th Apr 2018, 7:40 pm

Assuming the manual linked to in post #6 is the correct one, it's possible that the startup resistor (according to the manual, R6, 15K/5W) has gone open circuit.

This provides the control chip with initial power to get it going. After that, the control circuit runs from a supply provided from the transformer pin 1, rectified and smoothed by D7 / C15.

Also check R19, and R11, the 2 * 82K resistors in series.

A word of warning: Before attempting these resistance measurements, check that the input smoothing capacitors (4 * 100uF, high voltage) are discharged and if they are not, discharge each of them in turn with a resistor (say 47K) held in insulated pliers.

5th Apr 2018, 7:40 pm	#11
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,575	Re: Microvitec Cub 1431 Power but no picture. Assuming the manual linked to in post #6 is the correct one, it's possible that the startup resistor (according to the manual, R6, 15K/5W) has gone open circuit. This provides the control chip with initial power to get it going. After that, the control circuit runs from a supply provided from the transformer pin 1, rectified and smoothed by D7 / C15. Also check R19, and R11, the 2 * 82K resistors in series. A word of warning: Before attempting these resistance measurements, check that the input smoothing capacitors (4 * 100uF, high voltage) are discharged and if they are not, discharge each of them in turn with a resistor (say 47K) held in insulated pliers.