Can't even get started

[Watchkeeper]

After completing the build, as per instructions, I get to Step 2 - Test and Use. First thing is A. Check voltages. So I check the voltage at TP22, as instructed, and find 0V instead of the 3.3V expected. But there's no remedy offered! The instructions assume everything will be hunky-dory, but in my case it isn't.

A circuit diagram would be helpful. Is one available?

[MNTech]

The fourth page of the instructions has the diagram. If you didn't get this you may have a counterfeit.
https://www.jyetech.com/Products/LcdSco ... 38_new.pdf

If you have 5V but no 3.3V U3, the 3.3V regulator is probably bad.
Check for a short to ground on TP22. Before jumper JP4 is closed the only parts connected to this point are U3 and C22.

ChipQwik will help you remove U3 without damaging the board or the part.
https://www.youtube.com/watch?v=FTQqjggeklo

[Watchkeeper]

Thanks for that.I'll give that a go once the Christmas madness has abated.

[Edit] Guess what's on page 4 of the instructions ("when all else fails, read the instructions")? You're dealing with an idiot, I'm afraid!

[MNTech]

There is a kit with necessary QuipQuik materials.
The SMD1 removal kit cost nearly as much as the DSO138 but I'm sure you find other uses for it.
https://www.digikey.com/product-detail/ ... -ND/304148

The regulator is a LM1117IMPX-3.3/NOPB. It's in a SOT-223-4 package.
https://www.digikey.com/product-detail/ ... ND/3440160

Buy from where ever you like, the DigiKey links are for reference.

[Watchkeeper]

It's all good! I re-flowed the solder on the regulator pins and she's sprung into life.

I need to calibrate it and adjust the trimmer caps, but basically she's operational.

Thanks for your input, MNTech.

[MNTech]

I'm glad to hear you now have a working scope.
Out of curiosity, did you install the SMD parts or was the regulator done by JYE?

Loading the 113-13801-066.rar firmware upgrade is worth the effort. read the whole thread if you want to know why.
https://www.jyetech.com/forum/viewtopic ... t=20#p4543

[Watchkeeper]

Out of curiosity, did you install the SMD parts or was the regulator done by JYE?

The kit came with the microprocessor installed but everything else was loose in the polythene bag. This was my first ever experience with SMDs, so mea culpa. Lessons have been learned.

I bought the kit from melisocy2017 on eBay:

https://www.ebay.co.uk/itm/DSO138-2-4-T ... 1a3ac7a774

Loading the 113-13801-066.rar firmware upgrade is worth the effort.

Thanks for the link. I watched a YouTube video last night describing the firmware update procedure ...

https://www.youtube.com/watch?v=fDtqO2wDdHk

... so I've already ordered a USB-to-serial converter which is apparently needed to do the job. It'll probably be on a slow boat from China shortly.

https://www.ebay.co.uk/itm/USB-2-0-CP21 ... 1868740494

I first became interested in electronics in the early 1960s, passing the CGLI Radio Amateurs Exam in 1964. I remember Veroboard coming onto the market and Maplin starting up as mail-order, being named after the nearby Maplin Sands! An oscilloscope was the stuff of dreams and quite beyond my means. This kit is just amazing to me, so much so I've just presented one to No. 2 Son for his birthday. He was equally chuffed.

I'm off now to buy a couple of powerbanks from Poundland. I'll wire them in series and use them to power the 'scope.