Oscilloscope calibration issue - Page 1
Forum section: electronics / beginners

author: destroyfx
author_rank: Newbie
timestamp: October 29, 2014, 09:34:37 pm
content: Hi,I just got myself my first oscilloscope, a old 20Mhz analog one as recommended by Dave, instead of a USB thingy.It was totally not calibrated so I as able to adjust tho horizontal, I will do the vertical later when I will have the correct equipment but I thing I have something wrong with the CRT (I did not find it in the service manual.)The problem is that if I move the trace down, it move the the left.Any idea?Also, the 5X Mag in the sweep do nothing.

author: poot36
author_rank: Frequent Contributor
timestamp: October 30, 2014, 04:59:39 am
content: I would suggest these three things as a start, 1. Check that all of the voltage rails are in spec. 2. Clean all of the switch/variable resistor contacts. 3. If there are socketed ICs or other components remove them and clean the component leads as well as the socket and plug the component back in. It could also be a bad or out of spec component (most likely a capacitor) in the horizontal circuit. Be careful around the high voltage crt anode and electrostatic vertical and horizontal deflection plates!

author: KJDS
author_rank: Super Contributor
timestamp: October 30, 2014, 08:18:42 am
content: When an old car gets a little noisy, it's usually best to turn the radio up.If that's the only problem with your first scope, then use it as is, rather than taking it apart and risk making it worse.

author: oldway
author_rank: Super Contributor
timestamp: October 30, 2014, 06:35:37 pm
content: That's a rebadged HUNG CHANG OS-620, low end "made in China".http://diagramas.diagramasde.com/otros/HungChang_OS-620.pdfhttp://www.videosistemas.com/CIRCUITOS/OSCILOSCOPIO_HUNG_CHANG.pdfAs KJDS said, if you are not a specialist, don't try to calibrate your oscilloscope, you risk to make it worse.

author: destroyfx
author_rank: Newbie
timestamp: October 30, 2014, 06:49:30 pm
content: I did calibrate it. The only thing left is this small screen offset issue but I will leave that as is, for now.

author: destroyfx
author_rank: Newbie
timestamp: October 30, 2014, 07:30:21 pm
content: From what I read, it's a Korean OEM (Hung Chang Products Co. Ltd., C.P.O. Box 3125, Seoul (South-) Korea. Measurement equipment.)Tenma 72-720Elenco MO-1251Hung Chang OS-620Neotronics OS-620JDR Model 2000A-1 ElectronicsAW Sperry 620CTenma 72-320Dick Smith Q-1240Aron BS-601Degem System 112Ramsey Model 2200KB Electronics Model 33330OMRON PAN-8022and now, Ramsey BS-601 (miss labeling with the Aron or they put different model number for the same thing).I got the calibrations instruction from the Tenma 72-320 service manuel.I got the user manual for the Elenco MO-1251I got the schematics from pdf scan .. for the Hung Chang OS-620I think I have everything now

author: oldway
author_rank: Super Contributor
timestamp: October 30, 2014, 08:55:15 pm
content: And also OMRON PAN 8022 for sale on Ebay Germany as "Made in Germany" for...499 EUROS..http://www.ebay.de/itm/OMRON-Oszilloskop-PAN-8022-Neu-Deutsche-Qualitat-/261075222917?pt=Mess_Pr%C3%BCftechnik&hash=item3cc94bc185

author: poot36
author_rank: Frequent Contributor
timestamp: October 31, 2014, 04:22:37 am
content: Also look for dry cracked solder joints.