Yes that is correct. TP842 glitches but Q840 collector doesn’t. Looks like whatever is happening is only pulling the voltage down there by about 4 volts. It is weird as I’d expect Q840 to drop a bit there too but it doesn’t. I stuck the scope across both sides of it and did a differential measurement which matched. I have my suspicions the resistor isn’t healthy. It will be replaced with a nice fresh Vishay MRS25 when I do the dividers.
I have already ordered some fresh VR37 510k resistors. 50 of the things as it was cheaper than buying 6 from RS
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
... unfortunately back ordered due on 6th December.
Fuse is now sorted. I got some slow blow ones (arrived in a massive cardboard box big enough to get 2500 sheets of paper in covered in fragile tape. More
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
). Power up doesn’t pop the fuse now so the power supply is repaired and working. Runs pretty cool. After 30 minutes the bracket was only warm to the touch and nothing to worry about.
Can’t progress further yet so I am shelving this and fixing my 465 and 475A until the resistors arrive. Got a collection going now
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif.pagespeed.ce._hfWAz_QHO.gif)