HP 4261A LCR Meter

Brooke Clarke 2012
HP 4261A LCR Meter

Background
Description
Photos
Related
Links

Background

This is part of my interest in impedance measurement usually associated with component test.

Description

This LCR meter works at either 120 Hz or 1 kHz.  It was described in HP Journal, September 1976 (Price at introduction $1740).

As Received

Not working properly.
The output does switch between 120 Hz and 1 kHz, but the level is always at about 1 ACV no matter how the switches are set.
The units indicator is also locked on "H" no matter where the switches are.

The problem is related to the front panel slide switches not making contact.

Photos

Fig 1 Bottom
HP 4261A LCR
                Meter
Fig 2 Display Assembly
HP 4261A LCR
                Meter
Fig 3 Switch Assembly
HP 4261A LCR
                Meter
Fig 4 Top
HP 4261A LCR
                Meter
Fig 5 Switch Slide
HP 4261A LCR
                Meter




Note two screws under the top trip strip need to be removed to free the display assembly.  Instructions for this can be seen in Fig 4 on the tab that's part of the display bracket.
Removing the front panel requires removing 8 screws, the pull out instruction card and the nut on the external trigger button then the screws holding the PCB to the front panel.
The switch sliders will slide out of the assembly, but when putting them back it's a good idea to slide them in the direction that folds down the contacts rather than the direction that might bend them backwards.

The first try was to use a pencil eraser to clean the contacts an also form them slightly higher.  This resulted in now being able to make a marginal connection for capacitance mode, but it's far from a good contact.

De-Oxit on order.

Related

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Crystals, electronic
Crystal Temperature compensation Patents
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General Radio GR 650-A Impedance Bridge
HP 4260A Universal Bridge
HP 4274A & HP 4275A LCR Meters
HP 4328A Milliohmmeter
HP 4332 LCR Meter
HP 4395A Combination Network, Spectrum, Impedance Analyzer
Impedance Measurements
Marconi TF-2700 Universal Bridge
Transmission Line Zo vs. Frequency
ZM-4 Bridge battery powered
ZM-11/U Capactance-Inductance-Resistance Bridge, line powered

Links

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Page created 17 June 2003.