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Oscilloscope for beginner question

vholfx

vholfx

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I recently got a few dead boards for free, there's a 1 lost MVS board, a Tekken 3 a Kaneko board and a few others. Some turn on, some don't give any sign of life.

I know near to nothing about PCB repairs, but I definitely want to learn. I'm a programmer so I'm comfortable with logic, math, epproms, and a few other concepts, but I never repair anything electronic related.

I stumbled upon a somewhat cheap oscilloscope but I'm not at the point of deciding whether it is a good scope or not yet. It is a dual channel, 20 Mhz scope.

Is 20 Mhz enough for learning to troubleshoot PCBs? I've read 50 Mhz is better, 100 Mhz even more so. What is considered the minimum spec?

Here is the manual if you want to take a look.

https://1drv.ms/b/s!ApWphfoykW4hlWQvVQoljYHR6nJI

Thanks!
 
For context, I’ve been fiddling with boards for a few years though I’m no master yet. Honestly I bought an oscilloscope 6 months ago and haven’t had to plug it in yet. In the meantime I’ve fixed several boards though! So far everything has been solvable with a multimeter, $20 logic probe, soldering iron, some wire, an eprom programmer and whatever components I need for the fix. Also a very healthy respect for the MAME repo in github, and lots of data sheet googling. I am excited to plug in my scope but I think it’s overkill for a lot of repairs.

Like Tekken 3 for example... look for missing surface mount capacitors, that is pretty common with those. Just put one on if it’s missing and it’ll probably fire up! No scope needed.

Anyway there are some scope pros here and I’m sure they’ll chime in too. 20mhz should be fine for a lot of signals on a lot of 80’s and 90’s arcade boards btw. But for a lot of repairs you won’t be interested in looking at the signals timing, you’ll just be interested to see if it’s not doing what it’s supposed to (stuck low when it should be toggling for example). So your scope can show you, but a simple logic probe could too.

I remember this being a good jumping off point: https://forums.arcade-museum.com/showthread.php?t=177192 but this forum is super amazing too, folks usually jump in with insight on any given board.
 
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Thank you for your great input and that awesome thread link, I'll be reading that in detail.

Only a couple of months ago I barely knew what a jamma harness was, now I got a Naomi2 netbooting and I can troubleshoot basic voltage problems, I know the ins and out of my cab and I'm building a supergun for my workbench.

I love learning and I feel I'll definitely enjoy the hobby even more if I take the time to learn basic electronics / PCB troubleshooting.
 
on the tekken3 you strt by looking at the top board large customs for bent / damaged pins - very common.
then damaged or missing capacitors.
then check the bottom board for leaking capacitors - you WILL find some!


the neo is a different story, the most common problem other than battery damage is bad ram - but you need a way to test the surface-mount ones.
i have a 28pin soic adapter to put them in my universal programmer and run a ram test.

never worked on a kaneko board but i have many and they have a worrying amount of custom chips on them.
 
I echo what @ekorz said - a logic probe and multimeter will be much more useful for troubleshooting most board logic and voltage issues.

Oscilloscopes and logic analyzers have their place but they’re typically only useful once in a while when facing advanced issues involving timing and signal integrity.

I’d also prioritize picking up an EPROM programmer for dumping chips and programming new ones. It’s an invaluable tool for PCB troubleshooting and repairing.

With your Neo Geo board, try installing the Diagnostic BIOS-it’s really good at identifying bad memory of that is indeed the issue with your board.
 
ShootTheCore said:
With your Neo Geo board, try installing the Diagnostic BIOS-it’s really good at identifying bad memory of that is indeed the issue with your board.
Click to expand...
The diagnostic bios is SO GOOD.
 
What is an example of a good Logic Probe?
 
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