Unknown Issue with Hitachi V-1050F Oscilloscope - Page 1
Forum section: electronics / repair

author: ARAR-S2319 Rose
author_rank: Newbie
timestamp: December 03, 2024, 08:40:10 pm
content: Hallo, I recently bought a Hitachi V-1050F Oscilloscope from an eBay seller in seemingly great condition. Everything on the scope seems to work fine apart from the trace itself being... wonky?In the image above is meant to be a perfect circle on the display though it quite clearly is not, I've adjusted, tinkered, troubleshooted and researched for weeks but I just cannot figure out what the issue even is, nevermind how to fix it. The scope was connected to the line out port on my PC, which was playing two separate mono sine waves at 120hz on the left and right channel. Other media played into it, such as songs by Jerobeam Fenderson are also displayed very incorrectly. I don't know if the connection itself could be an issue or not but I am not at all an expert, just an enthusiast. I have tried recalibrating the scope and I've checked inside for any obvious damage but can see nothing out of the ordinary. I would massively appreciate any help, thanks! (I have never used a forum so if I have done anything wrong I apologise)

author: jdragoset
author_rank: Frequent Contributor
timestamp: December 03, 2024, 10:56:34 pm
content: Get the manual.Check vertical gain calibration of channel 1 and 2.There is also an x gain (sweep width) to check.

author: Harry_22
author_rank: Frequent Contributor
timestamp: December 04, 2024, 09:42:56 am
content: Have a look 1kHz signal.

author: tunk
author_rank: Super Contributor
timestamp: December 04, 2024, 11:28:10 am
content: No expert, but I think I would first use a multimeterto check the voltages of the two channels.

author: Mahagam
author_rank: Regular Contributor
timestamp: December 04, 2024, 11:37:13 am
content: Try swapping the inputs

author: CaptDon
author_rank: Super Contributor
timestamp: December 04, 2024, 01:35:43 pm
content: Please tell me exactly what you were expecting to see? If your answer is a single thin line at a 45 degree slant then you obviously have phase shift between X and Y. Is one A.C. coupled and one D.C. coupled? If you reduce the vertical gain it looks like you would get a circle. It appears the vertical gain is currently about 2X the horizontal gain.

author: CaptDon
author_rank: Super Contributor
timestamp: December 04, 2024, 01:41:32 pm
content: Why would you expect a circle??? You need 90 degrees of phase shift to obtain a circle. Is your laptop audio client capable of variable phase shift? Normally Left and Right outputs would show no phase shift and you should get one thin slanted trace at 45 degrees going from lower left to upper right. We need a bit more info about the signal generation. How are you controlling phase shift? It looks like your signal is whacked out, not the scope.

author: CaptDon
author_rank: Super Contributor
timestamp: December 04, 2024, 01:55:14 pm
content: Stereophonic musical information displayed as X Y can't be predicted although the mono content should form the slanted line. Any non-monotonic content will deviate from the singular thin slanted line. I think you are confused with what you expect to see with what you should really see.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 04, 2024, 02:23:12 pm
content: Nice old scope,I have mostly had imperfect Lissajous traces on old equipment.Everything has to be very well aligned and the input leads need to be near identical to get good lissajous pattern.Here is some suggestion:Put the same signal, perhaps a ONE KHz signal on both the A and B Channels using your leads. Or use Identical length BNC leads. See if they can very closely align with one another using vertical adjust to put them on top of one another and then amplitude. Once you do this then try the A vs B and you should get a 45 degree line as the Capt states. If you cannot get the same signal to be identical in both separate traces, you will not get the desired pattern. Your pattern suggests a 90 degree difference.wikipedia has nice diagram of different patternshttps://en.wikipedia.org/wiki/Lissajous_curve#/media/File:Lissajous_phase.svgedit: Please Adjust your probes using the compensate adjustment before doing anything else.

author: ARAR-S2319 Rose
author_rank: Newbie
timestamp: December 04, 2024, 07:44:37 pm
content: Thanks for the replies and advice!Quote from: jdragoset on December 03, 2024, 10:56:34 pmI have the operation manual (https://nscainc.com/wp-content/uploads/pdf/H_V1050.pdf) but could not find anything that helped, though a lot of it I could not understand. I have checked the calibration several times and it appears to be okay. Even after checking the manual I am not sure what you mean by checking the x gain sweep width, sorry.Quote from: Harry_22 on December 04, 2024, 09:42:56 amI tried this on each channel, channel 1 was displaying it very oddly, making a strange double sine wave thing, very cool looking but probably not correct.After leaving it for a bit, channel 1 very suddenly displayed it correctly (probably). The trace wasn't moving at all, unlike in the gif.I don't know what this means or if it's normal, but I do hope this is useful.Quote from: tunk on December 04, 2024, 11:28:10 amI currently do not have a multimeter, but I could maybe find one. I'm also not sure how to check the voltage of the channels but could probably figure it out.Quote from: Mahagam on December 04, 2024, 11:37:13 amAfter swapping them, I had the exact same result, but thank you for the suggestion.Quote from: CaptDon on December 04, 2024, 01:35:43 pmI was expecting to see a circle similar to the image below (Not my scope/image)As for the AC/DC coupling, both of the channels are the same cable, so coming from the same output on my PC. I am not sure whether it is AC or DC coupled as when I change the setting on the scope, it displays exactly the same thing. I have read that a line-out port from a motherboard is likely AC coupled.I tried changing the vertical gain and it was more circular but still far from normal, almost like a circle with a dent in it.Quote from: CaptDon on December 04, 2024, 01:41:32 pmThere was 90 degrees of phase shift (I think), I followed this guide.This image shows a 1kHz wave slightly adjusted so there should be a 90 degree phase shift (I have also tried adjusting it to see if it'd help but it always looks wrong). If you need more information regarding the signal then please let me know.Quote from: Wallace Gasiewicz on December 04, 2024, 02:23:12 pmThank you, I will give this a shot and read that Wikipedia page as soon as I get the chance and let you know how it goes. Would the compensate adjustment be the small red knob on the VARIABLE VOLTS/DIV knob? I am quite new to all of this and not great with terminology, sorry.Thanks again for the advice everyone(Quick edit, I have realised that the "gif" is now a static image, it is meant to show that the trace(?) is moving rapidly to the right, sorry)

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 04, 2024, 08:10:10 pm
content: Compensation adjustments are little screws on the oscilloscope probes, if you are using probes for input.The input lines to the scope must match, must be the same length and characteristics, otherwise phase shift will result. The higher the freq the more this is obvious on the screen.If you are using the stereo audio jack to supply the signal, is is probably out of phase at that point. Use the same channel, exactly the same source for both signal connections.The circle you were expecting is caused by two sine waves of the exact same frequency exactly 90 degrees out of phase. As you have discovered.