LeCroy DDA-120 as a general purpose scope? - Page 1
Forum section: electronics / testgear

author: rhb
author_rank: Super Contributor
timestamp: September 06, 2018, 03:03:08 am
content: How suitable are these as a general purpose scope? The specs look desirable, especially with the external 10 MHz ref input. Is there a gotcha I should know about? I'd expect to use it at 50 ohms to board test points such as U.FL connectors with 0 ohm resistor jumpers to enable them.

author: helius
author_rank: Super Contributor
timestamp: September 06, 2018, 03:46:32 am
content: It is perfectly usable as a general-purpose scope. I believe it is the same as the LC584AXL, but with additional software for hard drive analysis.

author: DaJMasta
author_rank: Super Contributor
timestamp: September 06, 2018, 04:04:31 am
content: The DDA 110, 120, and 125 are good general use scopes. I think the UI is a bit less streamlined for regular use compared to modern scopes, but it's probably a bit better for applying layers of math operations and such, but these DDA scopes have the same input ranges as the normal scopes, which is different from some later series DDA scopes that omit higher voltage ranges (though the 125 is less), so they're good for general use.Boot time is reasonably short and the interior metalwork is real nice looking too.

author: nctnico
author_rank: Super Contributor
timestamp: September 06, 2018, 07:43:00 am
content: Quote from: rhb on September 06, 2018, 03:03:08 amGenerally there is no peak-detect mode on Lecroy oscillscopes. This can cause funny effectns on some signals. IMHO that makes these oscilloscopes less useful for general purpose work especially at low samplerates. Think about a signal with narrow pulses. Without peak-detect this will look completely different.

author: rhb
author_rank: Super Contributor
timestamp: September 06, 2018, 10:31:33 pm
content: But for low sample rates I have other scopes with peak detect. The reason for my interest is it's a 1 GHz 4 channel DSO w/ 4 MSa/trace for well under $1000 with a 10 MHz reference clock input.I've not been able to find a service manual. Is one available? That becomes pretty important as things get older.

author: nctnico
author_rank: Super Contributor
timestamp: September 06, 2018, 11:00:41 pm
content: Quote from: rhb on September 06, 2018, 10:31:33 pmThere is a Lecroy group on Yahoo with a files section which has lots of service manuals. The DDA-120 is very similar to more common types like the LC584AXL. IIRC one of the potential problems is the automatic voltage selector in the PSU and the output connector of the PSU. Furthermore these scopes are rather noisy due to the fans. I looked into these as well but ended up buying an Agilent 54835 which I uphacked to a 54845 (1.5GHz / 8Gs/s on two channels). Like the Lecroy scopes these old Agilent scopes are not without problems. The internal timebase of the 54845 is pretty good though so it doesn't need an external reference.

author: DaJMasta
author_rank: Super Contributor
timestamp: September 06, 2018, 11:12:14 pm
content: No service manuals as far as I know, the main fan is a bit loud, but it's a single 120mm ducted to pull from the acquisition board, so it is replaceable with something more moderate. They're also physically large.... and I think it's worth mentioning that some are CRT models - I know the DDA-125 I had used an LCD, but the chassis had the space for a CRT, and I believe many earlier models (125 is based of the LC684XL or something) are still CRT based, so they're heavier.Let me amend that, there are service manuals for the non-DDA counterparts which are basically hardware equivalent, but if I remember right, portions of them were missing or were not component level? I think the acquisition board had some missing bits, but the PSU and CPU boards were available for the 684 series.

author: rhb
author_rank: Super Contributor
timestamp: September 07, 2018, 12:43:04 am
content: Thanks. I've posted a query to the Yahoo LeCroy group.