How to setup Atari Tempest on a Oscilloscope?

[DMGambone]

So I'm trying to diagnose issues with my Atari Tempest.

Per the many suggestions by others here, I've finally acquired an oscilloscope (Tektronix 2235A) to prevent damaging my 6100 that was working.

I've never used one before, so I need some assistance on understanding this tool. I believe I have everything connected properly.

Channel 1 probe connected to XOut + GND
Channel 2 probe connected to YOut + GND

The part I haven't really found info on is what to set the oscilloscope to. Lots of dials and buttons that I don't know what's right.

I have a bunch of questions like:
What's the Ch volts/div supposed to be set to? Dial and the AC/GND/DC switch below it

How to I specify XY Mode? I think I have it set right with 'Both', but want to confirm.

Thanks for any help.

 

[VectorCollector]

Read the manual. XY mode setting is shown and explained.

https://www.tek.com/oscilloscope/2235-manual/2235

Ideally, you'll use the scope in X-T and Y-T and X-Y modes to validate the signals. You should center/ground each in the middle horizontal line and have same vertical settings when doing X-Y. You can play with the vertical and horizontal settings to get the correct waveforms if using a known working UUT.

Play with the scope to best get used to it. It's a fun piece of equipment, don't fear it or be intimidated by it. LOL

HINT: some setting details shown below, it also shows all three modes as I noted above; search Google for more examples

 

[eschism]

Try turning your "A and B SEC/DIV" knob to the "X Y" position. Bottom of the knob.

 

[DTAR]

What voltages does the tempest need to run on the scope? Obviously 5v, but anything else?

 

[andrewb]

What voltages does the tempest need to run on the scope? Obviously 5v, but anything else?

You also need +15 and -15 for the video section. (Or +22 and -22, if you want to power it from before the onboard regulators.)

The easiest thing is to just run the board from the cab. I stick a milk crate in the back of mine, and set the PCB on it. The harness will reach, if you remove one of the screws holding it to the cab, to free up a little more slack.

 

[andrewb]

I have a bunch of questions like:
What's the Ch volts/div supposed to be set to? Dial and the AC/GND/DC switch below it

For safety, it's generally best practice to run a scope in AC coupled mode when you can. This basically puts a capacitor in series with each input, to prevent DC from getting to the scope. This will result in some distortion in the image (as the beam will sag when it draws long vectors), but it's safer, and it's the default mode the scope comes up in (or at least it is on mine).

You can switch it to DC coupling for both channels, which will make the image more accurate, but you run more of a risk of damaging your scope's inputs, if you do something dumb. Most of the time when using a scope with a vector, you're mostly concerned with whether you have an image or not, and if it's roughly correct, as you can't see small artifacts on the scope screen anyway. So you do need to test on a real monitor, but only once you're certain that the image is basically ok, and you test the AC and DC values with a DMM, to make sure they are ok (as a scope won't tell you the DC component of a signal, when you have it in AC mode.)

As for the settings, just adjust them to taste once you get an image. (I don't even know what I have mine set to, offhand. You just want the picture to roughly fill the screen.)

 

[DTAR]

Ok. Thanks. I don't have that cab to test, just the board. I wonder if it would be easier to get the regulator board to supply the correct voltages or just supply them directly to the pcb. Either way I'll have to get something to fully power the regulator board or something to get the voltage to power to xy section of the pcb.

 

[andrewb]

Ok. Thanks. I don't have that cab to test, just the board. I wonder if it would be easier to get the regulator board to supply the correct voltages or just supply them directly to the pcb. Either way I'll have to get something to fully power the regulator board or something to get the voltage to power to xy section of the pcb.

If you don't have a cab, the easiest thing is to get a brick and AR. You can technically build a circuit to make the +/-15, but you'd need a center-tapped transformer, and then a rectifier circuit. (Which is basically what the brick and AR are.)

 

[DTAR]

If you don't have a cab, the easiest thing is to get a brick and AR. You can technically build a circuit to make the +/-15, but you'd need a center-tapped transformer, and then a rectifier circuit. (Which is basically what the brick and AR are.)

Thanks. Know anyone in the Los Angeles area that has a brick for sale?

 

[andrewb]

Thanks. Know anyone in the Los Angeles area that has a brick for sale?

Nope, they're in demand, so they tend to sell quick. You could maybe ask Kalan714, as he tends to have a lot of Atari stuff.

There's also one on ebay right now.

Atari Arcade cabinet Isolation Transformer Power Brick Block WORKING Tempest | eBay

<p>Atari Arcade cabinet Isolation Transformer Power Brick Block with power cable. Bench tested WORKING Tempest. Condition is "Used". This came out of a tempest cocktail cabinet. I believe it also works in Star Wars, buyer would need to confirm. Check out my other listings for more tempest...

www.ebay.com

 

[DTAR]

Got my brick and ARII. But I'm having trouble getting a image on my scope, not sure if it works anymore. Is there a cheap digital scope I could buy?

 

[VectorCollector]

If you want to see the vector outputs, then an ANALOG scope is best.
If you want to debug the logic, then a DIGITAL scope is useful.
Lots of KLOV threads on this subject.

 

[andrewb]

What VC said.

Also, most scopes have a calibration output, which can be used to test to see if it's working.

 

[VectorCollector]

Yeh, what andrewb said - you can test your scope with the 1kHz 0.5V square pulse (typ.) calibration pins.
What scope is it? Got the manual?