Keysight E4980AL Precision LCR meter partial teardown

[nexus]

Hi all,

Did some work on one of my instruments here, its an E4980AL-032 (300 kHz option). The E4980AL comes in 300, 500 kHz and 1 MHz flavors. The E4980A is the high freq. version that goes up to 2 MHz, with some nice DC bias options (up to 40V internal DC bias capability). All E4980A/AL are rated at same accuracy spec of 0.05% with same measurement ranges.

I noticed that the LCD glass was showing signs of delamination (it is an EMI shielded glass, so it contains layers with metal mesh). So this gave me an excuse to open it up and take a peek inside. I have not seen any detailed board pics from inside the E4980A/AL meters online.

Full high-res photo dump: https://drive.google.com/drive/folders/1dR6SpquMtO1U3GbjPnZD62Gn6p-JvUbW?usp=sharing

Since you only have to disassemble the front end, I did not take the entire thing apart. The back is just the processor and motherboard, so those aren't very interesting. The neat bits are the analog front end which actually does the LCR measurement. I also took some of the shielding cages off to get better pics.

I was a little surprised at some no-clean flux still being splattered all over the connectors that were soldered in by hand. A little sloppy for a "high-end" instrument but hey, the customer usually doesn't see it so...

I also had to add some extra EMI tape to shim up the LCD to the front panel/keypad assembly. I noticed that there was a gap and every time you press keys near the lower-right of the screen, the glass would move in. Tolerances aren't that great on large, thin pieces of plastic like the front panel I suppose.

Enjoy the pics.

[HighVoltage]

Thanks for the teardown

It looks like the inside of the housing is nicely covered with some copper shielding on the surface.
I have been looking around for one but even used, the prices are pretty high.

[bc888]

Wow. Thank you for sharing!

[nexus]

It looks like the inside of the housing is nicely covered with some copper shielding on the surface.

Yup, the chassis is a 2 piece clamshell that screws together using 6 bolts, probably M4 as they use Torx T20 heads.
The plastic is metalized on the inside and attached to ground at several points to form a shield inside the instrument. The rear panel is metal so that is also a shield, and the front panel has a sheetmetal layer with fingers that touch the chassis all around the perimeter. They definitely take shielding seriously on these instruments.

The design is very similar to some other agilent/KS instruments I have repaired, such as the N1911A/N1912A P series power meters. In fact the E4980A/AL and N1911/12A use some of the same part numbers for the capacitive front panel button membrane, the LCD, and the LCD glass (EMI window), and even the same San Ace 60mm 12V fan (109R0612S4D011).

Keep your eyes peeled on eBay. The deals are far and few in-between but persistence and patience are key!

[analogRF]

is there any way to add DC bias to these?
is the circuitry already in there? can someone compare with E4980A?