When you are setting up a bench around calibration equipment standards, a null indicator is the component that tells you when a reference signal has been balanced to zero. It is a simple tool, but a reliable one matters. Newer or professionally serviced units can carry a serious price tag, so a vintage B&K 750 looks tempting. The listing, however, makes one thing clear: this is a piece with an unknown operational history. That detail changes how you should read the purchase.
Quick verdict The B&K 750 is a used, wired, blue test equipment calibrator null indicator listed at USD 49.00. The listing says the unit powers on but has not been otherwise tested, and it is sold as vintage with scratches and imperfections. That makes it a candidate for repair or parts, not a ready-to-use reference. If you are prepared to diagnose and restore it yourself, the price is a modest starting point.
Who it suits This B&K 750 suits someone who already works on old test gear and wants a restoration project. It also fits a technician who needs a donor instrument for another repair. If you need a calibrated null indicator straight out of the box, this is not the right stop.
What stands out from the listed details The listing is honest about cosmetics and function. It describes a blue unit with a wired connection, notes visible scratches and imperfections, and says the overall condition is still good for its age. There is no pretense that this is a fresh, polished instrument, and the description does not try to hide any of it.
Meaningful trade-offs The biggest trade-off is the unknown inside the case. Since only the most basic operation has been confirmed, you have no information about sensitivity, drift, or whether the null function works correctly. Older electronics can hide deteriorated components, so the real cost may include time and replacement parts.
The B&K 750 Test Equipment Calibrator Null Indicator If you want a low-cost B&K 750 to put on the bench and bring back to life, this unit gives you a starting point. The limitation is that it is not verified for calibration work, so you should assume it needs work before it can be trusted in a standards-based setup. That is the central trade-off: cheap entry, unknown performance.
Bottom line At USD 49.00, the B&K 750 is a vintage null indicator that powers on but has not been otherwise tested. If you can bring your own expertise and test equipment, it may be a worthwhile gamble. If you need a trustworthy reference today, keep looking.
