Products > Test Equipment
HP 3465A DMM repair
<< < (6/9) > >>
bd139:
The voltage is clamped at +/- 5V by the opposing circuit so it will never hit the 6v breakdown voltage, thus the B-E junction is fine.

(checked with LTspice)


Edit: this is actually wrong. I am clearly drunk driving LTspice at the moment. There is 9v across the junction  :-DD

JFET it is!
Zoli:

--- Quote from: bd139 on May 25, 2022, 05:28:55 pm ---The voltage is clamped at +/- 5V by the opposing circuit so it will never hit the 6v breakdown voltage, thus the B-E junction is fine.

(checked with LTspice)


Edit: this is actually wrong. I am clearly drunk driving LTspice at the moment. There is 9v across the junction  :-DD

JFET it is!

--- End quote ---
Sorry to ask, but CR10/11 isn't 3.9V Zener? Better check in reality, because I wouldn't trust the schematics... :-//
bd139:
CR10/11 are 3.92v zeners. CR8/9 are low leakage diodes. So the zeners set the clamp constraint plus one diode drop across the low leakage diodes.
Zoli:

--- Quote from: bd139 on May 25, 2022, 05:48:45 pm ---CR10/11 are 3.92v zeners. CR8/9 are low leakage diodes. So the zeners set the clamp constraint plus one diode drop across the low leakage diodes.

--- End quote ---
OK so (3.9+0.6)*2=9V; now I understand.
Caliaxy:

--- Quote from: bd139 on May 25, 2022, 05:48:45 pm ---CR10/11 are 3.92v zeners. CR8/9 are low leakage diodes. So the zeners set the clamp constraint plus one diode drop across the low leakage diodes.

--- End quote ---
Dat scan... The one in MrYakimovYA's link is much better. What's the expected voltage range in the node pointed by the arrow "See Note 5" during normal operation? What happens if you apply there, say, +3V?
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod