Iwatsu SS_7821 experiences... - Page 1
Forum section: electronics / testgear

author: edy
author_rank: Super Contributor
timestamp: August 02, 2013, 07:11:57 pm
content: Hi folks,I am looking to buy an oscilloscope and found a local shop carrying an Iwatsu at a reasonable cost. Only problem is it is apparently out of calibration. If the unit powers on and seemingly works, is it a big gamble or can I just compensate for the cursors or find some way to correct them? Is this a hardware or software issue, or backup battery issue? The other questions is if it was a simple repair why did they pawn it off for cheap? Or is it just a lucky find? Anyone with experience on Iwatsu and the quality of the brand let me know please.Thanks.

author: Unknown
author_rank: Unknown
timestamp: August 02, 2013, 07:18:32 pm
content: What do you mean with out of calibration? Did the date on the cal by sticker expire? Is the 'uncal' light that goes away when you lock the vernier adjustment in the calibrated position? Or are signals grossly distorted or have the wrong amplitude/frequency/DC offset?

author: edavid
author_rank: Super Contributor
timestamp: August 02, 2013, 08:54:34 pm
content: You can download the SS-7810 service manual from several places, including:http://www.iti.iwatsu.co.jp/manual/pdf/SS-7810-05-04_ServManl.pdfThe SS-7821 is very similar.If you do need to calibrate it, you will need to build (or borrow?) a test jig, consisting mainly of a 16 bit DAC. The schematic is in that manual, but it's a project.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 02, 2013, 10:47:23 pm
content: My old job bought a similar Iwatsu.It was a very useful & capable instrument.I wouldn't worry much about calibration --it's mainly so that companies can point to a calibration sheet to prove that their tests are to a specified standard.Good instruments do not drift that much that theyneedtweaking at regular intervals,so that for private use it should be more than adequate.

author: edy
author_rank: Super Contributor
timestamp: August 03, 2013, 03:27:01 am
content: The instrument was used in a government lab and was sold off at auction, but there is a label attached that says cursors are out of calibration and so measurements will not be correct.I am assuming the scope works fine, but when you pull out the little cursors and move them over on the screen to your signal, the number value displayed would be off.Does this make sense? I haven't seen this scope in action ever, so I am guessing that there are "cursors" that you can activate and they draw on the screen a little "+" sign, which you can slide up/down/left/right to some place on your signal if you want to measure say the peak on a sine curve or something. I assume the value at the cursor would then be given as a numerical value somewhere on the screen.I don't think that is a huge deal, probably can be recalibrated but wondering why they put a label on the scope, was it just too hard to calibrate or does it need special tools to get in and reprogram or change some settings?

author: G7PSK
author_rank: Super Contributor
timestamp: August 03, 2013, 08:48:30 am
content: The cursors measure voltage (vertical) and frequency/time (horizontal) when you switch to the horizontal cursors you get 2 vertical doted lines that you move to the relevant parts of you wave form, this then also gives a digital read out on screen, as the scope also has a digital frequency read out on screen you can compare the frequency readings in order to check how far out the cursors are, on the Iwatsu that I have (SS-7804A 40mhz)it can be quite hard to get the two to match due to the width of the cursor lines but as long as you always use the same edge on each cursor there is no real problem. Being ex government department they might have rejected the unit as unserviceable due to the cursors being out just in order to get the latest and greatest model out there and if they had to prove that the cursors were out they just deliberately used opposite edges. I ones got an ex government milling machine that was declared unserviceable, the reason "the paint was chipped" other than that there was nothing wrong with it. The military at one time used to buy vehicles with a supply of all the spares each vehicle was expected to use in its life time, I have seen bedford three and half tonners at auction with very low miles but the tail light is out, that vehicle has used up its quota of spare bulbs or lenses so of to the auction it goes. I think that things have altered recently but back in the days I used to go to the MOD auctions on a regular basis that was hoe it worked and if something did not sell or was not collected within fourteen days it went into a big hole. I would not be worried about a label saying out of call.