Show off your oscilloscope

[blargg]

I've been looking for months on craigslist and eBay for an affordable scope. I had missed a $50 Tektronix 2245 on craigslist a while back. Today I got a list-alert.com email that something with oscilloscope was just posted, and here this is for $50+$7 for me to drive there (the guy had FIVE of them for sale, $50 each):



These were from a university. I haven't found the manual but it looks like it's from around 1994. The inside is almost dust-free, suggesting that it's hardly been used:



It's got digital storage and cursors. More pics. Still looking for the manual to download (only found the service manual so far).

Better late than never!

[infiniteneslives]

Nice find! Looks like a pretty good one especially for the price

I got my old oscope from a university (which I attended) also. It was down in the basement in storage for a few decades, it's from ~1975 as near as I can tell. An old analog tektronix 5440 20Mhz, it's actually vertically oriented. Mine looks like it's from the stone age compared to yours I can share pics if interested.

[blargg]

Yes, post some pictures. I've updated the thread title accordingly

EDIT: Yes, I figured out how to use the EXT TRIG connected to $4016 read strobe and then do a one-time trigger started by reading $4016, that gets captured in the scope's 8ksample buffer for examination afterwards.

[koitsu]

Pots and buttons and a scope and BNC connectors and weird digital readouts. Hell if I know what you magicians do with those contraptions. :P

[infiniteneslives]

Bonus points for naming the signal pair



The three 'drawers' pull out breaking contact deep within the scope via card edge connectors.

[blargg]

DMC-generated square wave? Wild guess

Nice thing about the older scopes is that replacement parts are much easier to find. The later ones have expensive custom ICs galore. Heathkit made one which I bet is all off-the-shelf parts.

Here's that measurement I'd have loved to have done years ago, that took ten minutes now:

Code: Select all

; Setup
set_ppuaddr $3F00
mov PPUDATA,#$01
mov PPUDATA,#$11
mov PPUDATA,#$21
mov PPUDATA,#$31
...
; This is run once each scanline
set_ppuaddr $3F00
bit $4016 ; trigger scope
bit $2007 ; next palette entry
bit $2007 ; next palette entry
bit $2007 ; next palette entry
bit $2007 ; next palette entry

So simple to do now. But now there's little left to measure. Meh.

[koitsu]

You can try to figure out what's going on with that (non-DMA) OAM stuff. :-)

And infiniteneslives, that looks like a scope from Oregon State. :P

[infiniteneslives]

And infiniteneslives, that looks like a scope from Oregon State.

Good eye

DMC-generated square wave? Wild guess

Naw nothing that fancy, I was lazy and just took some traces off the cart.

[Grumskiz]

50$ for a Tektronix Phillips scope with digital storage...you don't know how jealous I am right now ;3
No, seriously: Great find! These go for at least 100-200€ around here, because you just don't see them that often.
If I wanted to get a cheap one I'd have to go with a russian one. Not that there is a problem with those, but they can not only be a pain to use if you don't understand russian , but also repairing them is nearly impossible. And I really don't get the analogue storage system they used.
Well I'm still looking at options around here, so I would be more than thankful for every recommendation!

€dit: I should learn to read first...

[Bregalad]

It's fun because I have exactly the same oscilloscope as you, and guess what, I got it from my university. They changed them to new oscilloscope and sell the old ones to EE students for a ridiculously low price.

I also have my dad's oscilloscope but it's even older. I think he bought it when he was a teenager and spend all his savings on it ^^

[Dwedit]

I'm still impressed by the old Youscope Demo. Play a WAV file and move the dot around on an oscilloscope in XY mode.

[Bregalad]

Not to be rude, but you need 2 signals to use the XY mode.

[Grumskiz]

Not to be rude, but you need 2 signals to use the XY mode.

The description of the video says that you need a 2 channel oszilloscope. The wave file is stereo, so it does actually use both channels to do these effects. I think this is also what Dwedit meant.

[tepples]

How much bandwidth do classic vector arcade games need?

[blargg]

Apparently it also relies on your DAC using sample-and-hold (i.e. unfiltered at the very least), which rules out most outputs. This makes the output quickly change levels (higher harmonics = sharper waves), which apparently several of the patterns rely on. So the fact that it's a wav is kind of misleading.