My new oscope arrived today : 72-3055

Smart Bomb

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My new toy arrived today...new, in the box, never used...a Tenma 72-3055 oscope.

I cant wait to learn how to use it.
 

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Looks too clean! You'd better start using it, pronto!

Also....we need to see the unboxing video. :p
 
Looks too clean! You'd better start using it, pronto!

Also....we need to see the unboxing video. :p
I didnt think of an unboxing vid...i will maybe get to use it before end of year...all my vector games are at my country place 45 minutes from me...i may go there this weekend and hook it up to an asteroids im attempting to repair.

It is NOS, NIB...it was in an electronics warehouse inventory and forgotten about for decades. I got to scoop it up.
 
Cool how they label Channel 1 as X and Channel 2 as Y. LOL
And has the blanking input on the back. Sweer.

Nice find. Use if for good and not for evil. :)
 
Cool how they label Channel 1 as X and Channel 2 as Y. LOL
And has the blanking input on the back. Sweer.

Nice find. Use if for good and not for evil. :)
I need to learn how to use it first before I can save the world...Im reading through the instructions now...im barely understanding it all.
 
Think of it as a voltmeter that simply tracks a voltage over time. (Y-T) The big trick is to fiddle with the trigger to get a stable signal.

Then in XY mode, it's like two voltmeters at once - one right to left, the other top to bottom. (Make sure both channels are same voltage setting and moved to the center horizontal grid). Without a blanking signal at the back, you'll see retrace lines when debuggin' vectors.

The easy part is getting waveforms.
The hard part is interpreting those waveforms.
 
Like this? LOL


For actually testing vectors, check out ArcadeDoc's vids (Classic Arcade Repairs).
He uses a scope (digi and analog) as much as he uses his Fluke 9010A and signal analyzer etc.
 
Like this? LOL


For actually testing vectors, check out ArcadeDoc's vids (Classic Arcade Repairs).
He uses a scope (digi and analog) as much as he uses his Fluke 9010A and signal analyzer etc.
Ive watched all of his vids...some more than once...he has the same scope. I watch him and jacklick's vids everyday. Ive asked them both questions on youtube.
 
I would suggest... if you have boards that are "known working" (tested in a cab say) that you can power up on a test bench - start learning to use the scope on things that will show valid signals to give yourself confidence around getting the scope setting right, without having to worry about the PCB.
So if you have a working vector game... hook the scope onto the X+Y outputs from the board and try and get the "right" image on the scope screen (set to XY mode, play with the voltage/gain settings on the 2 axis and the centring etc.)
Or hook a probe onto the clock and /RW lines on the CPU of a known good PCB - see if you can set the timebase and trigger to give a good image of what's going on etc. etc.
 
I would suggest... if you have boards that are "known working" (tested in a cab say) that you can power up on a test bench - start learning to use the scope on things that will show valid signals to give yourself confidence around getting the scope setting right, without having to worry about the PCB.
So if you have a working vector game... hook the scope onto the X+Y outputs from the board and try and get the "right" image on the scope screen (set to XY mode, play with the voltage/gain settings on the 2 axis and the centring etc.)
Or hook a probe onto the clock and /RW lines on the CPU of a known good PCB - see if you can set the timebase and trigger to give a good image of what's going on etc. etc.
I have a space duel, lunar lander and an asteroids and NONE of them have working boards....so nothing working to compare to. Id have to build a test bench being i dont have one..
 
I have a space duel, lunar lander and an asteroids and NONE of them have working boards....so nothing working to compare to. Id have to build a test bench being i dont have one..
Well if I were you I'd start with Asty or LL. To be honest I wouldn't consider trying to trouble-shoot PCBs in a cab, running on the bench is the best/safest way in my opinion.
It's fairly straight-forward to use a JAMMA PSU and a separate centre-tapped transformer (+diodes if needed) to give you all the voltages you need to run this stuff on then bench, then wire in a switch of the test switch and that's about all you need to get started.

Edit... see also: https://www.jmargolin.com/vgens/vgens.htm
 
Well if I were you I'd start with Asty or LL. To be honest I wouldn't consider trying to trouble-shoot PCBs in a cab, running on the bench is the best/safest way in my opinion.
It's fairly straight-forward to use a JAMMA PSU and a separate centre-tapped transformer (+diodes if needed) to give you all the voltages you need to run this stuff on then bench, then wire in a switch of the test switch and that's about all you need to get started.

Edit... see also: https://www.jmargolin.com/vgens/vgens.htm
That asteroids cab, the edge connector has pretty long wires...long enough to where if i made a little stand and set it at the back of the cab I could set the board flat on it and work it like its on a test bench. Thats what I plan on doing..I have some spare wood laying around i could make a stand in a few minutes.
 
That asteroids cab, the edge connector has pretty long wires...long enough to where if i made a little stand and set it at the back of the cab I could set the board flat on it and work it like its on a test bench. Thats what I plan on doing..I have some spare wood laying around i could make a stand in a few minutes.

I just stick a plastic milk crate in the back of my cabs when I want to troubleshoot the video section with a scope, and I rest the board on that. You can wedge it in the cab, leaning up against the AR, so it's at a slight angle. It works fine for Tempest, AD, and SD cabs. Never tried it with an Asteroids, but I wouldn't expect it to be too different.

However if I'm trying to debug the logic sections, I'll just power the board up on the bench using only 5V, and monitor the inputs to the DACs with a logic probe, to see if/when I have data there. You can get the logic sections of most boards to run with just 5V, using some tricks to disable the power-on reset circuit, on the boards that need it. (Basically just jumper across the diode in the reset circuit.)

Once I get the logic working so I have healthy data at all of the DAC inputs, I'll stick the board in the cabinet and check the video section with the scope (and test the XY outputs for DC and AC voltages with a DMM, to make sure they're safe), before I connect the monitor.
 
I just stick a plastic milk crate in the back of my cabs when I want to troubleshoot the video section with a scope, and I rest the board on that. You can wedge it in the cab, leaning up against the AR, so it's at a slight angle. It works fine for Tempest, AD, and SD cabs. Never tried it with an Asteroids, but I wouldn't expect it to be too different.

However if I'm trying to debug the logic sections, I'll just power the board up on the bench using only 5V, and monitor the inputs to the DACs with a logic probe, to see if/when I have data there. You can get the logic sections of most boards to run with just 5V, using some tricks to disable the power-on reset circuit, on the boards that need it. (Basically just jumper across the diode in the reset circuit.)

Once I get the logic working so I have healthy data at all of the DAC inputs, I'll stick the board in the cabinet and check the video section with the scope (and test the XY outputs for DC and AC voltages with a DMM, to make sure they're safe), before I connect the monitor.

@andrewb, if you're already testing with a scope, why do you bother with the DMM measurements? Scope should already give you that info. Either automatically or manually, depending on the scope.
 
@andrewb, if you're already testing with a scope, why do you bother with the DMM measurements? Scope should already give you that info. Either automatically or manually, depending on the scope.

My scope usually stays in AC coupling mode. :)

I also just like to see the DC number, as that's what really matters. It's just easier to adjust with the DMM, as for boards that have a XCTR/YCTR pot, you can tweak it and get the DC number as close to zero as possible before you connect the monitor. My 2465 doesn't have a DMM function.

I also mention it for pedagogical reasons, for folks who don't have a scope. All you really need is a DMM for checking the DC and AC voltages.
 
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