UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

mole42uk · 27th Sep 2018, 6:35 pm

Removing the -V supply to U103 settles the instrument down, the display reads 00.00 on any voltage range but it does respond to the range pushbuttons so I think the µP is working.

U109 may be the culprit but I've got no further than clipping the +V leg to that which made no difference to the -7V. I have ordered a couple of TLC271 chips to replace U103 - not only is that the regulator for the -7V but it's also in close proximity to the probe connections on the front panel.

27th Sep 2018, 6:35 pm	#10
mole42uk Nonode Join Date: Aug 2010 Location: Resolven, Wales; and Bristol, England Posts: 2,608	Re: I've injured my Keithley 175 DMM Removing the -V supply to U103 settles the instrument down, the display reads 00.00 on any voltage range but it does respond to the range pushbuttons so I think the µP is working. U109 may be the culprit but I've got no further than clipping the +V leg to that which made no difference to the -7V. I have ordered a couple of TLC271 chips to replace U103 - not only is that the regulator for the -7V but it's also in close proximity to the probe connections on the front panel. __________________ Richard Index: recursive loop: see recursive loop