New to me LT354 WaveRunner2 DSO - Page 1
Forum section: electronics / testgear

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 16, 2019, 12:26:35 pm
content: I recently found a used Iwatsu / Lecroy (also known as Wuerstchenscope's) LT354.It seemed to have been set aside in 2003 going by the stickers left on it and finally sent to the skip recently where my seller got hold of it then sold it as powering-up but otherwise untested.I couldn't pick it up locally so there was a little risk in receiving a scope that had more damage than it was worth.Once received, it appeared to have been through some bashing around, light scratches and marks all around, a couple of dents to the top, broken fan, bent PCMCIA cover, dead HDD, one damaged rear foot, two missing side feet. Fortunately it came with the front cover though!I like the colour LCD screen and the fact that it's a lot quieter than my 9354 or DDA-120 it may even be quieter than the TDS500 (If my memory is good.)As it needed some bodywork I had a good excuse to take it apart, the inside was very clean, almost dust free, many of the screws needed some re-tightening, I hope the heatsinked components in the PSU are not in the same case I didn't go that far.It was surprising not to find any HMM memory sockets on the acquisition board, this kills any hope to upgrade it to a M or L version some day, it's stuck with 250k points/channel.Looking at the service manual and scope's maintenance menu it looks like the HMM modules have been replaced, the flash ADC (MAD442) and acquisition memory (MAM633) have been combined into one component called HAM631.I can't find any hints in the service manual as to whether there are different versions of the HAM631 for M and L memory dephs.Does anyone know if the acquisition memory depth is software limited (firmware version, option keys) or maybe hardware limited (SMD jumper resistors configuration) or actually set by the type of HAM631 on the PCB?The service manual downloaded from KO4BB has no component list and appears to have the wrong PCB layouts as these do show the HMM module sockets.Does anybody have a better service manual than this?One small but annoying issue I have is the scope displays "Battery bad: Data may be corrupt" on startup.This is related to the fact that I have replaced the dead HDD by a CF card and PCMCIA adapter. The scope seems to be reading the backup battery status as if a SRAM card were being used rather than HDD.The annoying consequence is that I have to reinsert the adapter on every power-on or else I'll get a "No Medium Inserted" message when trying to access the CF card.Would anyone be able to recommend me a CF-PCMCIA adapter that does not cause this problem?

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 18, 2019, 01:31:46 am
content: I've just received more old CF cards, the issue seems more related to the types of CF than the PCMCIA adapter.I cut the 2 battery status lines in the adapter that shut the scope up about "Bad battery....", funnily that did not prevent it from not detecting the hard disk (CF) on a clod start. The card detect lines are held low by the CF card, what else am I missing.For now I have a 32MB Canon, and a 512MB unbranded Japanese made card that will be detected on a cold start. Two Transcend 512MB, one Lexar 128MB and a Fujifilm 128MB that need inserting after a cold start to be detected.Any ideas?I saw an old topic somewhere in EEVblog that mentioned overclocking the CPU on the Waverunner/Wavepro series, I looked into that, the PLL configuration jumpers were not too hard to find but I couldn't make sense of their order on the PCB and ended up going for DIP switches and trial and error.There is some speed to gain by swapping the positions of R8->R11 and R12->R6.

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 19, 2019, 01:07:12 pm
content: More questions still...The noise floor: I know this is probably a common question on DSO, just I don't know what should be expected on this model.Attached screen captures with no BWL, 200MHz and 20MHz, channels grounded in coupling menu, 250kpts/CH.One thing puzzling me (I'd already noticed this on the 9300 series) but the "Global BWL" in the special modes menu seems to have no effect, I haven't RTFM, anyone know what it actually does?I've done the math for CH2 (the noisiest one) on all V/div settings. To give the extremes it ranges from pp noise being 9% of full scale at 2mV/div to 2.6% at 0.5V/div without BWL. This falls to 3.94% at 2mV/div and 1.05% at 50mV&0.5V/div with 20MHz BWL.Does this sound/look normal?

author: tautech
author_rank: Super Contributor
timestamp: July 19, 2019, 08:28:46 pm
content: If it was mine I wouldn't be concerned with anything above, looks quite OK to me.Global BWL would be a mode that turns ON BW limiting for all channels with a single command IMO.

author: David Hess
author_rank: Super Contributor
timestamp: July 19, 2019, 08:32:53 pm
content: That level of noise is high but not high enough to indicate a problem. It is also consistent with the maximum sensitivity being only 2mV/div.

author: Mr Nutts
author_rank: Regular Contributor
timestamp: July 20, 2019, 09:05:28 am
content: Quote from: shakalnokturn on July 16, 2019, 12:26:35 pmSince you menation Mr W., have you seen his review of his Wavruner2 LT264?https://www.eevblog.com/forum/testgear/lecroy-waverunner-2-lt264m-review-and-(partial)-teardown/He wrote this about the sample memory:QuoteQuoteIt looks like the WR2 service manual contains the schematics and component list of the WR1. I couldn't find a new one, and when I asked Mr W. (who's now on the Allaboutcircuits forum) he told me that this is the only version that was releasedQuoteI've never come across this problem.The CF to PCMCIA adapters I have were made by Kingston, Sandisk and Transcend.Quote from: shakalnokturn on July 19, 2019, 01:07:12 pmI haven't seen this "Global BWL" switch so I can't answer that but you could ask Mr WQuoteWhy did you use pk-pk and persistence mode?Noise floor is normally measured as RMS and not Pk-Pk, and not while running persistence mode, so if your results look high this is why

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 24, 2019, 02:13:24 am
content: Thanks for all your answers, for now I'll assume it's a reliable new toy.I read across Mr. W.'s LT264 review, somehow at the time I read it didn't pay much attention to the Acq. memory detail.I must question the "This means that all scopes physically contain the maximum amount of sample memory (4Mpts per hybrid)" though: In the Service manual I read that the HAM631 contain 4 mega bits (not Bytes) of memory each. Shouldn't that mean a maximum of 512k points and 1GS/s with one HAM631?ThenI'm assumingthere are the Iwatsu acquisition boards and the Lecroy acquisition boards (CPU bard has a jumper to set which is being used), the Iwatsu Acq. would be used from the LT262 to LT354 with a single HAM631 per channel and not able to interleave them to gain sample rate and memory by interleaving.The Lecroy boards would be used in the LT372 to LT584 (and WavePro?) these would have two HAM631 per channel and allow interleaving channels to gain sample rate and acquisition memory.But... the service manual must be wrong or else the 4M points/channel don't fit into the LT372 and above.As for my noise measurements, well the p-p and persistence were really to get a view of the extremes... On this scope enabling persistence does not affect the averaged p-p measurements displayed on-screen.