Hey Bob,

What model of Hantek do you have?

The scope indicates you are measuring 128V? By chance do you have the probe setting to 'X1' and not 'X10'?

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I know, but one thing at a time. If the attenuator is set wrong, you could saturate the AtoD, causing the vertical scale to potentially look like it was not working. Granted, the other functions (i.e. time base) should have still worked.

Is anything working on the front panel? Buttons OK?

BTW, I have the same scope. Wonder if it is just a loose connector.

I'll see if I can round up a schematic too. is it still under warranty?

Bob,

There might be some interesting tidbits of info for the DSO5702P here: https://www.eevblog.com/forum/repair/hantek-dso5072p-oscilloscope-channel-1-drift/msg1840220/#msg1840220

Doesn't specifically address your issue directly, but it shows some voltage test points which might come in handy if you have to fix.

Also, I believe you can control the scope via the usb. It would be interesting if you can still do that.

Mines probably two years old. Still impresses me for what you can get nowadays for not a lot of money. There is a simple mod if you ever wanted to expand the bandwidth to 200MHz. I think it's just a resistor removal or add. Doubt if you would ever need that for a pin tho. If you look for the video to mod it, you might get an idea of what's inside and maybe spot a cable that if you took yours apart, could check. Don't do it if you think it's still under warranty tho. Don't want to void it.

USB: I'm pretty sure I tried it once, or at least watched the video. No real interest in actually using that feature, so didn't give it much more than a passing thought.

Your AutoSet button changing the scale is an interesting comment. I'll have to think about that. It looks like there's and input board, and I'm thinking the control panel might be a separate board? I'd dig up the 200MHz mod video and check it out.

Here's the inside from the 200Mhz mod video:
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Looks like a power supply board in the image.

Good for you Bob!

Bob,

Adding to Barack's comments: Here's a good thread on cleaning battery acid off a PWB.

https://pinside.com/pinball/forum/topic/stripping-battery-corrosion-with-a-strong-acid/page/2#post-5270047

Thanks for the kind words, many more smarter people here than me. I'm still just a newbie.

As a precaution, make sure the iron isn't too hot. If you're energetic, I think they make 'rivets' (for lack of a better word) that can be used to fix a broken via pad (assuming it's just a two layer board). We use them them for when we route prototype designs, but not for thru hole parts since we use surface mounted parts exclusively. We use them to ties traces together between layers.

In many years prior, we actually repaired loose traces with glue. This was an acceptable practice at the time, and worked rather well. Don't recall what glue we used, but I think it was an epoxy. Of course, we were very careful soldering on the repaired traces - but they did hold.

LOL, I didn't even notice he started that thread. No doubt, I didn't pour it down the drain...or even have it in the house. Didn't need a lot of ZEP, just brushed some on, then rinsed well in the yard. Wore safety glasses, old clothes, and gloves too!

The 'Default Setup' button is the factory reset (for what it's worth)...

Just pressing the button sets it to default. I assume 'Cancel' will return it to the prior setting. If you were already at default settings, then I suppose it looks like it didn't do anything.

Bob,

The 4051 is pretty straightforward. Depending on the the level on A,B,C lines, it will select one of the X0-X7 inputs/outputs and connect it to the X (common) pin. Let's say you want the signal to go from X3 to the X (common), you would set Enable to low, set Select C, B, A to low, high, high (respectively). I highlighted this below in red and yellow. Want the X0 to X (common) connection? Set Enable to low, set C, B, A to low, low low - and so forth. Don't want any connections? Set the Enable to High to disable all the switches. You can have only one (or none) connection (i.e. you can't have X1, X2 on at the same time).

Think of it this way: It's just 8 switches (X0-X7) that go to a common connection (X). To pick what switch you want, set the the Select (i.e. the address) C, B, A appropriately along with having the Enable low.
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To answer your question Quench, it would be the C line is stuck low.

Maybe that was a test for Bob? LOL Sorry if it was...

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That trace appears to be ground. Its likely for a RF connection to a shield or cover. EMI or similar type of connection. Look at where that board goes and check for fingestock, conductive foam, etc. Either it lowers an emission or grounds a RF hot spot on the board.

Even tho Quench has been steering this ship...I feel a little left out here. LOL!

But you're in good hands...

Nah, other than my simpleton comments about the 4051 and the EMI shielding, I haven't been following the thread very closely. You're doing a great job!

Adjust the sweep time longer to catch all 63 cycles. Use the Single Seq button to catch the start of the 63 pulses. It will only trigger once (it won't keep sweeping). Make sure you set the trigger level to catch a real pulse (like you did above - that's probably OK other than you might have the x1 x10 setting wrong).

Sorry if I missed something, just butting in here for a few while I got a free sec.

FYI: The Single Seq button makes the scope only trigger once, it won't keep sweeping. So one it triggers at xx volts, it does a full sweep and stops. And it won't sweep until the input goes above the trigger level. If the time base isn't long enough (i.e to catch all 63 cycles), then you won't be able to count the pulses Quench is referring to. If you slow it down, then you should be be able to see all the pulses.

Make sense?

I have the same Hantek DSO5072P Bob has. I wasn't worried about Bob zooming in - thought that might muddy the waters. But yes, he could do that.

Bob, try hitting the F7 button. I think that allows opening up a window to zoom in. i.e. does a longer sweep and you can still zoom in to examine closely.

Not sure how much memory it has.

Bob,

F7 is hiding here:

You can see the wider sweep up top, but still zoom in below via the red brackets.
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Looks like you are getting there. Now increase the sweep time to catch the number of pulses you are interested in.

Is the scope probe ground connected? You have some noise on that trace.

Looking at your screen Bob, the complete cycle (on-off-on) is about 1.6uS. x64 = 102.4uS Set you scope to around that for a full sweep and you should see all the pulses Quench is talking about.

Set the sweep time longer to see more pulses if you are trying to count 63 pulses.

Time to call it a night!

Sorry, I'm confused...

Bob is trying to see 63 or 64 clock cycles, correct? Then, ideally, maybe see a delay. Bob's plot below is in the nS range, so the plot he captured is a single clock cycle, no? Why doesn't he increase the sweep time in order to count the pulses?

Might be a moot question if you are try to capture a specific event.

Regardless, finding a proper trigger would be the way to go if he can somehow get a probe on it.
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Bob,

Do you have a micrometer? If you cant read the full part number on the IC, then just measure.

Bob,

Removing/replacing the 4051 should be rather painless.

1) First off, note the pin 1 mark, dot, etc.

2) The simplest way to remove is to use two irons with a wider (chisel) tips, or maybe just a normal tip placed at an angle. But not high wattage! It won't need much heat to flow the solder - it's just a little part. You can actually add solder so that it bridges the pins on each side to help transfer the heat. Plus use some 63/37 or 60/40 (lead) solder since the scope is likely RHOS. Lead free solder melts at a high temp is somewhat of a PIA.

3) With an iron on each side and solder melted, the part will easily slide free. Shouldn't damage any traces. Don't force it, it should slide off like butter. Watch out for the bypass chip cap right next to the IC. Thank goodness there's no thermal pad to unsolder on the bottom of the part - that would make it a lot harder.

4) Use solder wick to clean up excess solder on the pads. It will probably be a mess due to the extra solder, but the solder wick will take care of it.

5) Place the new part on the pads, use just a small amount of solder on opposing corners to anchor and center up the part. Solder the remaining leads, and then correctly solder the first two joints used to anchor the part. Too much solder? - just wick some off. Check the pin 1 mark.

Easy peasy. I'm an old fart and have been using surface mounted parts for many decades. For the most part, I'd much rather work on surface mounted parts than thru-hole. At work we even use 0201 (0.02 x 0.01") parts and we are going smaller, but I admit I use bigger parts due to my line of work. You might want to get some thin solder.

You might be surprised how easy it is to replace/install if you have steady hands.

Got an old board to practice on?

Quickly tinning the part's lead prior to installing will help a lot. Don't need much, just a light coat. You can also add a little solder to the opposing pads so it's all set to go. Again, not much is needed - just enough to hold it in place and solder properly afterwards. Just take the eraser end of a pencil (or something similar) and hold the part in place, hit the opposing leads, part will settle in place because of you holding it in place - secured. No need to overthink it. I would think the tape would be a big PIA and is not needed.

0.031" solder - give it a try and make sure you don't short between pins. Smaller might be better, but 0.031 is definitely OK.

You'll get the hang if it - it really is not hard if you have halfway decent soldering skills (and you do). Too many post on Pinside about SMT being this weird and hard thing to work with since it's new to them. It's just not.

If you're really worried about it, just buy this and practice first: A few dollars, and money well spent to calm your nerves.

https://www.amazon.com/s
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That is some interesting stuff. I don't think you need that since your part is so small. In the demo the chip was huge - so that does look useful in that instance.

On a side note, he did make a very good comment...don't drag the iron and solder wick across the pins when cleaning.. Just down and up, then move over, repeat. Also, that was a pretty good size iron for the little pads to use w/the solder wick. If I was removing excess solder, I'd use a smaller iron.

Also, not all solder wick is created equal. Some has very little flux, and it can be a little bit of a pain to get it to wick up solder. Add some rosin flux to it if it doesn't take solder well. Good solder wick will really pull solder away.

I thought about the residual low temp solder, but once you wick it up, it will be gone. Any minuscule amount will simply mix with a lot more fresh 63/37 and be a moot point.

344C seems VERY hot. 63/37 should melt around 180 - 190C. I'm not opposed to applying a fair amount of heat to make the job go quickly. To me, 'not much heat and taking forever' to get the job done is by far an easier way to damage a board rather than 'hot and fast' with a little more heat - withing reason. 344C seems way too hot. WAG, but 250C'ish should be enough, depending on the tip. Hence, my comment about globing solder over all the pins to heat them up all at once with a bigger tip, and sliding the part off. Fast and done...

After you get the hang of this, you will officially be known as "NewSchoolBob".

Not really Bob. It's just a connection, it can be repaired with some greenwire. I design high power transmitters for a living, and I've vaporized huge traces when things go wrong. Rather speculator when it happens, resembles an arc welder going berserk - but we just repair the traces and go on.

Looks great!

The round diodes are a little bit of an oddity nowadays. Like Quench said, the IC looks fine.

I've used the square'ish 'MELF' PIN diodes in my designs for decades - never knew the round ones were considered MELFs too!

Bob, I'd be a little careful using tweezers with the caps and resistors. The small parts can be a little fragile. If you accidently give the tweezers a little twist or nudge after one end of the part is soldered, you can break the end of the part. Try using a small wooden toothpick (trying to think what else you might have laying around) to gently holding the parts in place by applying a miniscule amount of pressure from the top. After you get good at it, you probably won't even need to hold them in place.

The caps have a bit too much solder on them...but no harm. You just want a nice fillet. You could always wick excess solder off for appearance sake, but at the risk of damaging the part by fooling around with it too much. By the time you got to the IC, looks like you were getting the hang of it!
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I doubt if you fried it.

You and Quench were doing all the work, i justed started chiming in at the end.

Regarding the diodes, you're probably seeing a sneak path thru the other circuitry, especially since it is more than one diode. I doubt if you would have multiple diode failures. If you want to really verify, remove the diodes.

I know you really want to do this ...But then common sense kicks in a says "Don't tear apart the new scope." LOL, I wouldn't either.

Nah, easily done more than thru hole. I think we managed to to convert Bob. Been doing it for almost 30 years, would never go back to thru hole.

No biggie Bob, you got yourself a new scope!