Will my dsoshell 15001k be ok after giving it 18v instead of 9v? - Page 1
Forum section: electronics / beginners

author: snow
author_rank: Contributor
timestamp: January 10, 2022, 08:28:40 pm
content: hey y'all, (not sure if this is the right place to post this) i just finished building a DSOshell 15001k DIY oscilloscope kit, and to test it, i accidentally used an 18 volt power supply instead of a 9 volt one. will it still be ok? or will i have to get it swapped out? i didnt hear any components pop or anything.

author: snow
author_rank: Contributor
timestamp: January 10, 2022, 08:31:47 pm
content: and if you're wondering why I gave it 18v instead of 9v, its 'cause I play guitar and I had a daisy chain power supply wall wart laying around, and I used it 'cause I thought it was a 9v PS, but it's and 18v PS. but I didn't check to see if it supplied 9v before using it.

author: Manul
author_rank: Super Contributor
timestamp: January 10, 2022, 10:43:41 pm
content: Quote from: snow on January 10, 2022, 08:28:40 pmI don't really understand a question. Either it was not damaged and it works or it was damaged and it does not work. Have you tried? Does it work?Generally speaking the result of such event depends how the device is designed and what parts were used. This one seems to have only the LM1117-3.3 linear voltage regulator powered by 9V. LM1117 absolute maximum is 20V I think and it also has thermal protection. So all should be ok.

author: tunk
author_rank: Super Contributor
timestamp: January 10, 2022, 11:20:29 pm
content: The ICL7660 doesn't like more than 10.5V, and if it's an unregulated18V supply, the light load voltage could be well above 20V. Look at theschematics below and measure the test points.https://jyetech.com/dso-150-shell-oscilloscope/

author: Manul
author_rank: Super Contributor
timestamp: January 10, 2022, 11:31:25 pm
content: Quote from: tunk on January 10, 2022, 11:20:29 pmThat's a good point, I've totally missed the "analog" part of the schematic. Situation does not look so good anymore. At least ICL7660 is not a big deal and can be replaced.

author: snow
author_rank: Contributor
timestamp: January 11, 2022, 12:16:35 am
content: Quote from: Manul on January 10, 2022, 10:43:41 pmwell it works (i havent really messed with it yet, it just turns on and the controls work), but the on/off switch doesnt seem to do anything.

author: Manul
author_rank: Super Contributor
timestamp: January 11, 2022, 12:55:40 am
content: Quote from: snow on January 11, 2022, 12:16:35 amOn/off switch seems to be bypassed in schematic. Don't ask me why. You can remove R30 (0R jumper resistor). Does it show signals properly? If yes, then it survived. Astunknoted, the negative voltage generator was the most likely to fail. In that case I assume it would work, but would not show signals properly.

author: snow
author_rank: Contributor
timestamp: January 11, 2022, 02:13:09 am
content: Quote from: Manul on January 11, 2022, 12:55:40 amhow can i test if it shows signals properly?

author: snow
author_rank: Contributor
timestamp: January 11, 2022, 02:26:31 am
content: Quote from: Manul on January 11, 2022, 12:55:40 amand it turns out r30 bypasses the on/off switch

author: Gyro
author_rank: Super Contributor
timestamp: January 11, 2022, 09:56:21 am
content: The TL082 / TL084 opamps should be ok as they are rated to survive +/-22V (assuming that the 7660 output actually made it to anywhere near -18V). The LM1117 regulators in these things have been reported to fail sometimes (potentially non-genuine), but if this one survived the overvoltage then it's probably not a weak one. The other things that would have sufferedsignificantovercurrent are the display backlight LEDs which are fed from the unregulated supply. If the display is still illuminated evenly then they should be ok. Many of the electrolytic caps are also not rated that high - check for any bulged ones.Quote from: snow on January 11, 2022, 02:13:09 amIn the absence of other equipment, connect the probe tip to the 1kHz output, set the coupling to AC, and check that you get a symmetrical square wave about 0V. Check that you get a nice stable trigger on rising and falling edges. Run through the sensitivity ranges and check that the waveform gets bigger (reaching over full scale) and smaller appropriately.

author: snow
author_rank: Contributor
timestamp: January 12, 2022, 03:59:24 am
content: Quote from: Gyro on January 11, 2022, 09:56:21 amis this what is supposed to happen?:https://imgur.com/a/TsCsN4Q

author: Gyro
author_rank: Super Contributor
timestamp: January 12, 2022, 06:04:12 pm
content: (It's always worth attaching images to your posts, external links inevitably become orphaned over time.)No, that doesn't look right. It seems to be showing a large negative offset on the waveform. Strangely the waveform looks to be roughly the right size (on 5V/div) but it should be centred on the channel position marker (green arrow on left hand side of the screen). With the 1kHz input removed, you should also get a flat line which lines up with the marker.Try moving the trace vertical position and see if it moves at all. Off the top of my head, it may be that the positive supply to the analogue board opamps has failed.

author: snow
author_rank: Contributor
timestamp: January 12, 2022, 06:59:57 pm
content: Quote from: Gyro on January 12, 2022, 06:04:12 pmhow do i do that?

author: Gyro
author_rank: Super Contributor
timestamp: January 12, 2022, 07:05:10 pm
content: Best that you read the instructions to familiarize yourself with its intended operation. That will speed up your fault-finding and understanding what isn't working properly.

author: snow
author_rank: Contributor
timestamp: January 12, 2022, 07:17:04 pm
content: Quote from: Gyro on January 12, 2022, 07:05:10 pmok, i did the VPos allignment, but the vpos still like to move around alot

author: Gyro
author_rank: Super Contributor
timestamp: January 12, 2022, 07:26:32 pm
content: It sounds as if it's time to get the meter out and establish what is happening to the supplies on the ICs on the analogue board. If the supplies are all ok, then it may be a damaged IC. It's probably best to look around the U5 (the ICL7660) but there could be a problem anywhere, for instance, burned out R26 or R27 or damaged electrolytic caps downstream of them.At least t looks as if the 3V3 logic supply to the CPU and display is ok. Other parts are cheaper and easier to replace in comparison.EDIT: When you say "but the vpos still like to move around alot" maybe the probe is picking up noise. Try shorting the probe clips. Also check again to see if you get a symmetrical (AC coupling) squarewave waveform above and below 0V (the green arrow).

author: snow
author_rank: Contributor
timestamp: January 12, 2022, 08:40:13 pm
content: Quote from: Gyro on January 12, 2022, 07:26:32 pmi removed the clip from the probe and now the VPos isnt moving around nearly as much, but it is still slowly going down a bit.

author: snow
author_rank: Contributor
timestamp: January 14, 2022, 02:31:54 am
content: voltages:V+: 5.6AV+: 4.2V-: -4.9AV-: -4.1V1-V3: 0V4: 1.3

author: Gyro
author_rank: Super Contributor
timestamp: January 14, 2022, 10:46:38 am
content: If V+ is only 5.6V then it indicates that you are not feeding the board with 9V (more like 6.4V). The logic supply is regulating ok and the +/-AV voltages indicate that the 7660 -ve rail generator is working and there is no excessive current drain on the Analogue board. Maybe your (unregulated) 9V adapter isn't rated for sufficient output current.Feed it with the correct voltage and the trace will probably stabilize!

author: Peabody
author_rank: Super Contributor
timestamp: January 14, 2022, 03:54:26 pm
content: Your DSO150 is a newer version than mine, but to reset the vertical position on mine, I disconnect the leads, move the input switch on the back to GND, then hold the left button down until it says it's resetting the vertical. That moves the left indicator to the middle, and that's also where ground is. Then I move the input switch back to DC and test the squarewave generator on the back, which should give you a square wave from ground to 3.3V. I don't know if the newer versions work the same way.

author: snow
author_rank: Contributor
timestamp: January 14, 2022, 11:55:38 pm
content: Quote from: Gyro on January 14, 2022, 10:46:38 amyea rn im just using a 9v battery with a battery clip thingy

author: snow
author_rank: Contributor
timestamp: January 15, 2022, 01:05:30 am
content: for some reason my truetone onespot power supply isnt working with it, but the battery clip does work.

author: snow
author_rank: Contributor
timestamp: January 15, 2022, 01:07:46 am
content: and the battery is at about 8.5v

author: Gyro
author_rank: Super Contributor
timestamp: January 15, 2022, 10:44:27 am
content: Your battery is probably 8.5V open circuit, but is dropping significantly (to around the 6.xV figure when under load - maximum voltage drop of a 1N4007 diode is around 1.1V at it's full 1A rating (so less in your case).I can't comment on why your mains adapter isn't working. Maybe it isn't rated for enough current and sags too low, maybe it has excessive ripple (Have you checked the polarity of its output even?).The little 9V battery won't survive for long (it is failing already). If you want a portable setup, you would be better to get a 6xAA battery holder. That ought to give reasonable battery life.There is a thread on the JYE forum about using alternative battery sources, including internal lithium - but I really wouldn't advise that at your level of experience.https://forum.jyetech.com/viewforum.php?f=19&sid=0d35785e52febca7607085b79162322d

author: m3vuv
author_rank: Super Contributor
timestamp: January 15, 2022, 12:19:28 pm
content: I honestly dont know why people bother with these chineese toys that are like sommat that fell out of a christmas cracker!

author: Gyro
author_rank: Super Contributor
timestamp: January 15, 2022, 01:14:03 pm
content: Because theyweredirt cheap (<$20 pocket money price - I haven't checked Ali, but they're really pricy on ebay now). They at least allow visualisation of low frequency signals. Basically the scope equivalent of a really cheap DMM and a fun beginners kit to build. Occasionally handy to be able to stick one in your pocket.Irrelevant anyway, as the OP already has one.

author: Peabody
author_rank: Super Contributor
timestamp: January 15, 2022, 04:09:27 pm
content: I've found mine to be surprisingly useful. I converted it to battery power, and it's convenient sometimes to have a scope that isn't reference to earth ground. I'm just a hobbyist, and wasn't really interested in spending hundreds of dollars on a bench scope. Never had any luck finding Dave's $50 used analog scope. My latest use was to put it across a shunt resistor in a solar 18650 charger with load sharing, to see if the battery voltage ever went negative. It did. And it's useful in decoding IR remotes, and other slow things. No RF of course, but it was $20. Banggood is the place to buy them if you want a genuine one. And it isn't just junk from the Far East. The manufacturer provides documentation, and even firmware updates. They have a forum, and respond to emails. I think it's one of the best gear purchases I've ever made.

author: snow
author_rank: Contributor
timestamp: January 15, 2022, 08:37:33 pm
content: so am i gonna have to replace the 7660?

author: Gyro
author_rank: Super Contributor
timestamp: January 15, 2022, 08:44:30 pm
content: Quote from: snow on January 15, 2022, 08:37:33 pmWhy?Didn't you read the replies?

author: snow
author_rank: Contributor
timestamp: January 15, 2022, 09:53:09 pm
content: Quote from: Gyro on January 15, 2022, 08:44:30 pm'cause someone said that the 7660 doesnt like more than 10.5v, and the scope doesnt seem to work with wall power. so im thinking the 7660 should be replaced (or maybe the LM1117s since someone else said those fail sometimes)

author: Gyro
author_rank: Super Contributor
timestamp: January 15, 2022, 10:42:02 pm
content: No, because the voltages you posted indicate that they are both working. See my reply #18.If it's working with a battery then you need to check the mains adaptor specifications.

author: snow
author_rank: Contributor
timestamp: January 15, 2022, 11:06:12 pm
content: wait i just used a different outlet, and used a small extension cable and it works now, and the vpos is stable.

author: snow
author_rank: Contributor
timestamp: January 15, 2022, 11:09:50 pm
content: and it looks to be displaying the signal correctly!

author: Manul
author_rank: Super Contributor
timestamp: January 15, 2022, 11:13:24 pm
content: At least take a new 9V battery. Alkaline type, not that carbon-zinc. Or get AA battery holder. Or get regulated 9V adapter (probably switching type). Maybe use this oportunity and get an adjustable lab power supply. Your choice, but a proper supply is a must.Update: congratulations.

author: snow
author_rank: Contributor
timestamp: January 15, 2022, 11:23:49 pm
content: thanks for all the help!!

author: Gyro
author_rank: Super Contributor
timestamp: January 16, 2022, 09:39:01 am
content: Glad it's explained / sorted.Don't forget to get an electrician to sort the faulty outlet, or at least tape it so you don't forget in future.