Just nabbed myself a fairly clean looking HP 1740A off ebay. Unfortunately it was dead. Quick poke and prod session showed that the -15V and 8V rails were off.
Pulled off pass transistor for that rail and fired it up and the thing sprang into action. Seems ok, at least after the power supply!
Investigating the power supply lead to an interesting discovery. Transformer secondary connector appears to have melted and taken half the board with it.
This is what I discovered..
![HP 1740A power supply burn up 818109-0](https://www.eevblog.com/forum/index.php?action=dlattach;topic=206241.0;attach=818112;image)
Decided to pull the connector out and it fell to bits in my hand unfortunately.
![HP 1740A power supply burn up 818127-1](https://www.eevblog.com/forum/index.php?action=dlattach;topic=206241.0;attach=818130;image)
After desoldering the burned connector and rectifiers I am left with this:
![HP 1740A power supply burn up 818115-2](https://www.eevblog.com/forum/index.php?action=dlattach;topic=206241.0;attach=818118;image)
![HP 1740A power supply burn up 818121-3](https://www.eevblog.com/forum/index.php?action=dlattach;topic=206241.0;attach=818124;image)
I've just tested the bridge rectifiers and caps and they are all fine. This suggests that it was the connector or the soldering on the board that caused this.
Anyone have any repair tips for this one? I did professional rework years ago and this was "nah chuck it" territory.
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif.pagespeed.ce._hfWAz_QHO.gif)
I am considering:
1. Clean and grind out any charring.
2. New connectors on both ends.
3. Lift any burned up traces and jump with thick copper wire.
4. Apply copious amount of Kapton tape.