I am having an issue with the res led scale. I get 3 or 4 red led on at the same time, but thenyellow scale is working correctly.
I have replaced the 3914 drive chip, the 311 comparator, various transistors and fets, checked resistors and capacitors and the circuit wiring but can’t track it down.
Has anyone else seen this issue before?
Any help will be greatly appreciated!
Howard
Hi, I would say the following: most of the issues are from obscure quality components and/or human error such as microscopic interruptions on some traces (due to the poor PCB laminator transfer) or cold soldering points and also PCB not thoroughly cleaned as MCL constantly insists on his all videos. Also, missing vias ! Make sure that the via that is underneath the 3914 IC is in place and soldered/tested. Pay special attention to Q8 which in the video MCL mentions that it needs to specifically be soldered in reverse (as in: up side down) see video !! RED and Green LEDs are specific !!! They need to be of the exact part number !!!. Also. all ceramic caps have to be purchased to have a have low leakage factor !!! Once again, everything has to be squeaky, clean !. The FR4 PCB type itself has to also be of a very low leakage type as well !!! The suggested part number is mentioned in the provided docs. As a general rule of thumb avoid buying components from cheap and cheerful sources. Otherwise expect some weird and unexpected results. Pay special attention to all VR’s quality and that you do not drip flux inside them !. If you somehow managed to do it well…. the only solution is to literally flood the whole board with acetone / lacquer thinner. Do not attempt to use isopropyl alcohol as it doesn’t do it ! Good luck. PS: if the building procedure, materials used and calibration procedure followed by the book, the tester produces guaranteed repeatable results no doubt !
Just wanted to add that Q9 is to be mounted the same way as Q8 (up side down) but it is all explained in the video. Good luck. 👍Pay special attention to Q8 which in the video MCL mentions that it needs to specifically be soldered in reverse (as in: up side down) see video !!