My dear HP141T but we have a trouble......there is a single dot on display, no light on IF 8552B section.

On IF 8552B section two rear fuses are broken, inside on the 141T the fuse on 12.6V is broken also, with the schema I need to see/check the circuits (possible burned resistors or so on) and the voltages before to substitute the fuses. You can follow here below the hunt of the fault and repair!

  • This is a part of Power Supply schema with four reference voltages.
  • How the Power Supply for -12.6V running.....mumble mumble....
  • Fuses and so on.
  • Power Supply PCB.
  • Instead of -12.6 unfortunately the output is more or less -21V! Probably Q4 (TO3) is broken but not only in fact the voltages are incorrect on Q11 transistor also. Ok let's go!
  • I have subtituted the original TO3 (Q4) transistor with 2N3055 and the other original transistor (Q11) with BC237 and we will see..
  • After the transistors substitutions and the necessary trimmer adj. the output voltage of the -12.6 Power Supply is correct!
  • The calibrated signal is dislayed ok.
  • The HP14T is perfectly operational again and I'm on cloud nine!