Help with HP 1707A oscilloscope repair

[picofarad]

Yes, it's connected to transformer pin 10, through a diode.
It doesn't seems to be open (I measure about 1.2 ohms through the inductor) but it's not working (it's burnt and with a magnify lens I can see a crack in the middle of the component).

[mij59]

Yes, it's connected to transformer pin 10, through a diode.
It doesn't seems to be open (I measure about 1.2 ohms through the inductor) but it's not working (it's burnt and with a magnify lens I can see a crack in the middle of the component).

Don't think there's a problem with the inductor, you can compare it  the resistance of the inductor just below.
Check the diode, capacitor and the power supply rail for shorts.

[picofarad]

The resistance is the same as the other inductor. The diode is ok and the cap isn't shorted. But when I've turned on, smoke coming from the inductor and voltage rails all messed up: +80V rail is now 24 V and +15 V is now 2 V.

[mij59]

The resistance is the same as the other inductor. The diode is ok and the cap isn't shorted. But when I've turned on, smoke coming from the inductor and voltage rails all messed up: +80V rail is now 24 V and +15 V is now 2 V.

The +15V powers the low voltage regulator (page 20), check Q3, Q4 , and the -15V rail.

[guitarmike000]

WOW PICO! this is crazy stuff! very glad i have 2-1707b's don't envy you at all but i truly hop you can fix it.   mike