How does one test an old oscilloscope (Hitachi V-355)? - Page 1
Forum section: electronics / repair

author: UnkaHeemee
author_rank: Newbie
timestamp: April 01, 2023, 03:40:32 am
content: I will possibly buying an old Hitachi V-355 scope from a stranger. It doesn't have any probes. It turns on and produces a solid green tracer line. He's willing to let me have it for about 50 dollars.I have never owned one and definitely don't know how these things work ( watching YouTube vids to get basic idea).I want to know how I can safely test this thing once I have it and what else I might need. I found themanualfor it.I am not in a good spot financially so this seems like a good opportunity for me. I'd really appreciate some help and support.

author: C-47
author_rank: Regular Contributor
timestamp: April 01, 2023, 09:33:19 am
content: With a read of the manual you are mostly there, you will need to obtain a probe to be able to connect to the test point of the machine and that will give you a good idea of its working condition. As an aside, selling an oscilloscope without probes would start to raise questions. Also the attached maybe of help. Alan.https://www.eevblog.com/forum/chat/how-to-test-an-analog-oscilloscope-before-buying/

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: April 01, 2023, 10:30:32 am
content: Consider the costs of probe. Probe should have the same capacitance listed on the scope, otherwise trace is distorted.I think the capacitance of the probes is 25 pF. Check Manual and then see how much they cost.You need two probes. 10X probes.This is definitely a low freq scope at 35 MHz. Consider that. Do you want to measure more than signals at 35 MHz?

author: jonpaul
author_rank: Super Contributor
timestamp: April 01, 2023, 01:25:38 pm
content: We bought German Hameg 1 ch 10 MHz, 2 ch 20 MHz at Marché au Puces and Vide grinier (street sales) in Paris € 5,€25Beware dead/dim CRT, abused mechanical, damaged connectors and controls.DO NOT buy off epay, CL etc unless you can meet the seller and tes it.DO NOT SHIP they will be damaged in handling and are seldom packed well.Test is easy, no probes,,,CH 1 >>any wire from BNC center>>scope CAL for 1 kHz sq waveRepeat with CH2.Check focus, brightness move traces up/down pos, check every VER V/div and every HOR TIME/div controlJon

author: UnkaHeemee
author_rank: Newbie
timestamp: April 01, 2023, 04:26:12 pm
content: Quote from: C-47 on April 01, 2023, 09:33:19 amThanks for the link.Unfortunately I won't have probes with me when I go to pickup the thing. Why is it concerning that the scope is missing the probes? The person who is selling it says its an estates sales thing and he doesn't even know how to use or test it.Quote from: Wallace Gasiewicz on April 01, 2023, 10:30:32 amI don't see any capacitance listed in the manual. What are the usual terms used for that?So far, the max signals I've come across are the 14 ish MhZ clock signal from a C64. By the time all the processing is done and it reaches the CPU, it drops to about 1. I intend to work on old electronics or small arduino based projects.Quote from: jonpaul on April 01, 2023, 01:25:38 pmThanks for the suggestions.However, I am not sure how to interpret the test method you suggested. Are you asking me to connect something to the input channels and then do something?

author: Neepa
author_rank: Regular Contributor
timestamp: April 01, 2023, 05:25:34 pm
content: Quote from: UnkaHeemee on April 01, 2023, 04:26:12 pmThe Input capacitance is listed under "Input Impedance" of the Vertical Deflection System. pF as in Pico(a trillionth)-Farad is what you're looking for.As for testing you should make sure that every switch, rotary or sliding, is working correctly mechanically and is actually switching something.For the screen itself there is usually a Focus knob and a Brightness/Illumination knob. The former expands and contracts the scanning dot or trace on the screen. Going from fuzzy like 360P video to sharper and then fuzzy again. The latter increases or decreases the brightness of the dot or trace. At around halfway travel of the knob there should be a perfectly visibly trace/dot on the screen without sunshine shining on it directly. If it is still dim or hardly visible it is evidence of "tired" CRT screen. Which is unrecoverable apart from getting a CRT tube with less operating hours or even a new old stock one.For the Horizontal Deflection or "Timebase" it should vary the scanning speed of the dot across the screen. Going ever faster the further you decrease the scanned amount of time.The Vertical Section/Input should vary for a given constant signal the displayed amplitude. And do so so it looks symetrical if split horizontally along the graticules of the screen.For the position knobs those should vary the space over or under the displayed line, or "trace", for the Vertical Postion and the centricity for the Horizontal Position. With the latter the whole scanned line will vary left to right and can be even made to begin away from the edge of the screen towards the center.For analog scopes all turnable knobs that don't have detents when you turn them are usually variable resistors, called Potentiometers, and those can get dirty due to intruding dust or other dirt. Any glitchyness or sudden jumps on the screen when turning them is evidence of that. To clean those there are various cleaning sprays but those are best used only in moderation! Do not coat the whole inside of the Scope with them.Taking the Potentiometers out by desoldering them and carefully prying open the crimping to pull them apart and clean them with isopropanol alcohol can be done. If you can desolder and have reasonably steady hands. The alternative would be to desolder the old ones and and put in new ones with the same resistance values, shaft length and diameter.More I can't think off off the top of my head. If you don't want to troubleshoot any receiver sections of radios or anything beyond 80ies computers it should serve you fine for the beginning. Anything audio it will do and also the slow clocks of Arduino or anything Z80, 8088, 6502, 68000. The only problem with digital signals is it has no storage capability. It only displays continuous real time signals. So viewing split second events of a C64 RAM bus will require some patience and squinting.

author: edavid
author_rank: Super Contributor
timestamp: April 01, 2023, 07:23:36 pm
content: It's not a bad scope, but very basic. I think $50 is on the high side unless it's in really great condition.You don't need a probe to test it. Just bring a 1 foot length of wire with both ends stripped. You can connect that between the calibrator output and each input BNC in turn. Yes, you will have to look at the manual and a tutorial or two to figure out how to display a trace. If you can't handle that, don't buy a scopeAsk to look at the rest of the electronics stuff from the estate, and maybe you will spot the probes there.If you buy the scope, you can get the cheapest China probes and they will be fine - examples:https://www.amazon.com/Sumnacon%C2%AE-P6100-Sensitivity-Oscilloscope-Probe/dp/B00XJH2M02https://www.ebay.com/itm/165961133020ETA: I didn't notice you were in Canada - $50 Canadian is an OK price.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: April 01, 2023, 10:20:16 pm
content: Input Impedance on Page 32 of manual. 25 pFAs has been pointed out cheap probes are OK. The ones that have switch for 1X-10X can be problematic, So I just stick to 10X for now.Since you don't have the probes to check it,As edavid pointed out you do not need a probe to check the scopeIf you use the calibrator to see if the channels work and just use a wire, it will work but you will not get a nice square wave.

author: jonpaul
author_rank: Super Contributor
timestamp: April 01, 2023, 10:25:11 pm
content: self test: Scopes have a test point with a CAL signal on panelConnect: Place a bare wire or even a paper chip in INPUT CH 1 and thasn CH2Touch the clip or wre,The hand pickups up stray mains freq a few volts.Jon

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 02, 2023, 04:26:34 am
content: $50 for 35MHz? Eeehhh, I wouldn't pay that much...

author: Bud
author_rank: Super Contributor
timestamp: April 02, 2023, 07:21:53 am
content: $50 CAD is Nothing in Canada these days. You cant even fill your car fuel tank for it.

author: UnkaHeemee
author_rank: Newbie
timestamp: April 02, 2023, 03:20:40 pm
content: Quote from: Neepa on April 01, 2023, 05:25:34 pmDude! You're a legend!That's one of the simplest way to explain it all to a noob that I've ever come across.Thank you all for your inputs.So I did some basic tests on the scope and everything seems functional. I don't have probes or a foot long cable now. But I do have jumper wires and so I tested the built in test with it. Here is the output:It's set at 0.5 V div and 0.2 ms time/div.Is this the sort of square wave I am supposed to be seeing?Also! The trace needs rotating. Do I need to use a plastic screwdriver or something? I am afraid of putting a metal one inside that hole.

author: edavid
author_rank: Super Contributor
timestamp: April 02, 2023, 03:43:33 pm
content: Quote from: UnkaHeemee on April 02, 2023, 03:20:40 pmNo.(But don't bother until you get the scope where you are actually going to use it.)

author: tunk
author_rank: Super Contributor
timestamp: April 02, 2023, 03:54:34 pm
content: That looks like 1kHz, which it usually is. Not sure, but I think theamplitude usually is 1V; Is the red center knob on volts/div turnedall the way up?

author: UnkaHeemee
author_rank: Newbie
timestamp: April 02, 2023, 04:16:46 pm
content: Quote from: tunk on April 02, 2023, 03:54:34 pmYes. I turned it all the way to the right until the red light turned off.What is the significance? Please educate!

author: tunk
author_rank: Super Contributor
timestamp: April 02, 2023, 04:27:44 pm
content: Googled a bit and it could look like the face plate says .5V,and if that's the case, then it's fine.Edit: And maybe check ch2 as well.

author: jonpaul
author_rank: Super Contributor
timestamp: April 03, 2023, 02:52:19 am
content: OK fine, check ch 2 same way.Trace,rotation, is almost good, any tiny screwdriver that fits, not critical. Very small adjustmentJon

author: UnkaHeemee
author_rank: Newbie
timestamp: April 08, 2023, 03:02:20 am
content: Just posting for the sake of closure.Tested both channels with 100 Mhz probes:Had to use the adjustment tool provided with the probes to trim them until the outputs looked the way they do in the above images for channels 1 and 2. Looks like it's all working okay so far.