Agilent U1602A handheld scope - teardown

[zaoka]

Here it is
Got this scope of eBay for $400, brand new.

Its 2 channel, 20Mhz, 200Ms sampling.

Case is built well, very thick plastic, however, no metal shielding.

Scope works nice for me and what I do (electronic repairs). Auto mode is very fast, display has high contrast and very good angle view.

Multimeter is another story, its slow responding (including bar graph) and did not impress me at all. Definitely not Agilent standard. Also test lead terminals are soldered directly to the board and you can see soldering imperfections already on a brand new meter.
Resistance and capacity are very slow. To measure 100uF it took almost 8 seconds. DC or AC voltage is shown in 2-3 seconds.

[zaoka]

More pictures.

[Kiriakos-GR]

I can not throw my hat for a DSO with screen, but yea looks nice for what it is.

[Rufus]

Thanks for sharing.

The design seems a bit dated for 2007. Good deal for the money, the B version is still current and not much different.

[glowitz]

I just purchased a used (but looks virtually new) Agilent U1602A on eBay as well. This unit was built in Korea around mid 2007 and has the original calibration certificate. I'm noticing some things and wanted to compare notes with those of you out there (including the original poster Zaoka) who own this model. I'd also be curious for any owners of the Agilent U1602B (or U1604A or U1604B) to chime in so I can assess whether my unit is working correctly or not.

Observations:

0) SELF CAL. It passes the internal Self-Cal but there is about a 1mV DC offset on the Scope inputs. One is negative, the other is positive. Is that typical?

1) BATTERY LOSING CHARGE. The battery only holds a charge for about 20 minutes, but should be 4 hours. The indicator shows it's fully charged, but it then drains rapidly. It's about $80 for a replacement battery from Agilent -- is there any hope that this can be restored? Supposedly the meter wasn't used much (it still has the original LCD plastic protector and original packaging) and it does look virtually new. However, the 7.2V Battery is probably suffering from low usage and extended storage. Will multiple charge/discharge cycles help to restore the life? The manual mentions for very first time use to charge it with the unit ON for 25 hours. I haven't tried that yet. I did the quick charge method overnight with the unit turned off.

2) STRANGE VOLTAGE RAMP IN DCV METER MODE. When set to the Meter mode and DCV is enabled, I see a regular ramping in voltage from about 100mV to 650mV (approximately), which repeats on a regular basis. This is with nothing connected to the Meter inputs. I also get the same result on the logging mode -- and see a repeating sawtooth on V vs. T. Is this some kind of demo or test mode? What is going on here? If I short the inputs together, then it reads 0.0 mV, as expected. But what is this voltage ramping thing? Do all U1602A / U1602B / U1604A / U1604B units exhibit this behavior? I didn't see anything in the manual about it, so was curious whether this is some kind of auto-ranging trying to kick in or something...while it's looking for an input signal.

3) CAN'T SET DATE. It is not possible to set the DATE or TIME on the unit. I did notice a HEX code where the time is and read an Agilent service note that this means the internal battery backup (CR1220) is dead and how to replace it. So, that is likely the cause of this issue. Just pointing it out for those who may eventually experience the same issue. Do the new "B" models eliminate the battery or use a different battery? Just curious. And how long should this coin-cell battery last under normal use for this unit?

4) CAN'T RESET FACTORY DEFAULTS. Not sure if this is related to the coin cell battery issue above, but it is not possible to restore factory defaults

5) LOGGER MODE DOESN'T RESCALE CORRECTLY. When logging in the logger mode, scaling doesn't seem to work right. For example, if I have a lineraly increasing resistance -- say starting at 1K going to 10K in 1K steps....it will show an expected "staircase" pattern. However, when it reaches the overrange for that display setting, the scale will adjust to accommodate the higher value, but the historical part of the graph doesn't scale accordingly. As a result, all historical data on the screen is not scaling in proportion to the range change that took place. This happens both on the Y axis, as well as X (time) axis. When it reaches the end of the time axis and rescales the time, it doesn't adjust the historical part of the graph to shrink as well. This is a major bug and I don't know whether this could also be due to the memory battery issue (even when plugged into AC) -- or whether it is really a software defect. Can someone verify the performance of their unit to see what should happen? Please also state the firmware version.

6) DMM METER MODE SLOOOOOOOOOW. This issue was noted in the post above. It is almost useless -- as it takes several measurements to stabilize over several seconds. And even then, it seems to kind of jump around more than I would expect. Is the processor in the "B" model faster? Anyone know?

7) LCD DISPLAY FLICKER. There is noticeable flicker on the LCD display (especially against the gray background). I tested it without lights on to make sure it wasn't interference between the 60Hz and the display raster. It even flickers outside. It's not horrible -- but you can see it "twinkling" with some subtle random background noise which seems to be raster/scan related. Does anyone else see this issue on the "A" model or the "B" model? Is the display in the "B" model any better than the "A" model?

FIRMWARE. There may be a more current firmware version that could address some of these questions and I'll try that next -- but the release notes don't really say much about these particular issues. For reference, the current loaded version is 2.5.6 with Key Version 3.2.1. What is the Key version?

Hopefully someone out there sees this and we can compare so I understand what's expected and what needs to be fixed...

Happy testing!

[zaoka]

I sold mine long time ago.
Its outdated scope.

[lazyace]

Just in case anybody comes across this nice post googling...

I picked up one of these scopes the other day. Mine had garbled date and time as well until I replaced the internal primary button cell. Attached is the service procedure from Agilent.

Mine also needed a replacement 7.2V NiMH battery pack as it was down to only 500 mAh but the battery is very expensive from Agilent. So, I decided to "build" my own. Normally, I buy the individual cells and solder them together but I found a place that has a pre-tab-welded/  mostly assembled pack for a decent price ($32 at this time): http://www.batteryspace.com/customnimhbattery72v4500mah42apolyswitchwtableadscu-mm117pid5032.aspx

I also purchased some 80 mm PVC wrap to make it look professional: http://www.batteryspace.com/PVC-3.15-inch-80mm-Width-Shrink-Wrap-3-L-for-DIY-Battery-Packs.aspx

The only thing you need to do then, is transcribe the 10k temp probe and connector from the old battery pack. The new pack already has a fuse similar to the old one. I have some pictures in the next post of the process.

Interestingly enough, even though Agilent markets these packs as 4500 mAh, inside are only 4300 mAh batteries! The original batteries are made by GB (Model GP450LAH). I have attached the datasheet. The replacement batteries are six "4/3 A Fat" size batteries. The batteries I used are rated at 4500 mAh (Model # MH-4/3AF4500 by aaportablepower).

I did some capacity tests on the new batteries and the seem to be quality cells and actually provide their rated capacity. My tests show a nominal 4600 mAh for the pack (0.1C charge; 0.2C discharge down to 1.0 V IAW IEC). Yes, it took forever to test!

And, FWIW, I don't have any issues now that I have fixed the above and updated the firmware to 2.7.1. There have been a lot of changes since 2.5.6!

[lazyace]

Pictures of Agilent U1571A: