Buy yourself a cheap CRO for board testing

[Marty Machine]

As the title suggests, if you can find yourself a cheap CRO (Oscilloscope) it will be a VERY handy piece of test gear for you guys tracking down cpu-card faults....

These old cpu's only run at 1MHz to 4MHz typically, some later boards might be up at 8-10MHz, or more??
So, your CRO only needs to be capable of displaying say 10-20MHz signals.
You can get them cheap on Ebay, otherwise a NEW one from Dick Smith, Jaycar or Altronics is quite good.

The 10MHz ones are a great (cheap) starting point, and will cover most (if not all) probs on pinball cpu cards....

DICK SMITH :
10MHz
http://www.dse.com.au/cgi-bin/dse.storefront/4a2103f61692137a273fc0a87e010678/Product/View/Q1803
20MHz
http://www.dse.com.au/cgi-bin/dse.storefront/4a2103f61692137a273fc0a87e010678/Product/View/Q1822


JAYCAR :
10MHz
http://www.jaycar.com.au/productView.asp?ID=QC1920&keywords=oscilloscope&form=KEYWORD
20MHz
http://www.jaycar.com.au/productView.asp?ID=QC1922&keywords=oscilloscope&form=KEYWORD
40MHz
http://www.jaycar.com.au/productView.asp?ID=QC1924&keywords=oscilloscope&form=KEYWORD


ALTRONICS :
20MHz
http://www.altronics.com.au/index.asp?area=item&id=Q0150

Hope this helps....
MM.

[ddstoys]

Hey Marty
             A simple guide to using these would be great.  Ive worked out the basics but like voltages but thats about it lol also if you touch it on your skin you get a cool pattern lol

[Marty Machine]

Cool, is there anything in particular you don't know/want to do with your Cro? (besides sticking it on your hand or in your gob).

I might write up a beginner guide too, stay tuned.....although there's probably a bunch on google i guess?

MM.

[ddstoys]

Well mainly when im testing pulses all i get is a big fat light across the screen like its pulsing that fast its a big blur.  So i know im getting a pulse but how do i read this?

[Marty Machine]

Well mainly when im testing pulses all i get is a big fat light across the screen like its pulsing that fast its a big blur.  So i know im getting a pulse but how do i read this?

Do you know what the signal is meant to be doing? is it constantly pulsing (cpu master clock) or is it a temporary pulse from a switch input or something?

You should adjust the timebase switch and watch the pulse on screen, the pulse(s) will get narrower (more of them on screen) or wider, so wide that you miss it. (sounds like what you see now).

Also try adjusting the 'trigger' knob, you should see the pulse appear (or not) as you adjust the trigger setting.


MM.

[ddstoys]

It was when i was testing the clock pulse on a sys80 cpu it said that another pin had opposite shift or some crap but i couldnt tell as it was just a blur.   I did adjust all the setting but couldnt get a nice pulse going it fairly old so it might not be able to read that frequency?

[Marty Machine]

Pretty much all Cro's will read 5-10MHz nicely as old as it may be...

What brand/model is it? i can maybe lookup specs etc...and get a better idea of what controls are on it..

It sounds like your triggering needs to be adjusted, which also may include other associated switches like 'trigger' level' 'trigger polarity', you could switch your input switch (where the probe plugs in) between DC and AC etc etc...

[ajlaird]

I might be able to offer a good deal on the Jaycar 20MHz and 40MHz CROs on a multiple order through my company.

Mods, let me know if this is OK or not - I haven't read the rules that closely - so I won't post any details unless approved.

[ddstoys]

Thanks for your help marty its a BWD 530a    And here is a picture of the controls.  I did try looking up instructions on using a Cro but ran out of patience lol

[Marty Machine]

Nice, the old BWD's are ace Cro's, gee i used them at school ALL those years ago....
That model should easily handle pin-cpu signals, no probs.

I'd start with setting the trigger (between the probes) to Channel 1 (assuming you use channel1 probe for your measurments).

Set the volts/Div so the signal almost fills the screen height makes it easier to read.

Select the 'trigger' button at top-right to also be AC/DC (same as your probe setting AC/DC, and anything that relates to channel 1 etc.

Probably also play with the 'level' control, down under the green dot sticker...it should help trigger the display at various level of your signals.

that's a start 


AJ:
I reckon you should organise thru the moderators to offer a special AP Cro-deal for our newbies.
You might crack a decent order for 10 Cro's at a better discount price to help them on their way...

Hmmm, a Cro & MMeter might make good prizes in any upcoming meets & raffles hey?

just my 2c
MM.

[Strangeways]

I might be able to offer a good deal on the Jaycar 20MHz and 40MHz CROs on a multiple order through my company.

Mods, let me know if this is OK or not - I haven't read the rules that closely - so I won't post any details unless approved.

I can't see it being an issue if the members benefit and you are willing to organize such a deal. It is not against any rule(s) that I can think of. I'll have a quick chat with Tony and Nick.

[Retropin]

Aaaah CRO's!!

 Ive had a few....

 2nd was the DSE one which is a nice model and purchased for $80 new - i forgot it was on top of the pin when i went to play it and it fell off and broke.
Yesterday i bought the jaycar one - slightly more expensive and IMO - not as good as DSE ( DSE have run out.. only have voice activated animated flowers for sale or an LED massager)

The Y position doesnt work.. so back it goes today.

 Me and CRO's dont mix!

[Marty Machine]

Me and CRO's dont mix!

Some people just aren't meant to have a Cro heheheheeh