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New to Apple II & Troubleshooting

Gary C said:
I am using that Owon, and its great for general use and 99.999% of all the diagnostics on vintage PC's I have done, but I have had to use the Hameg traditional scope once on a higher frequency signal to really see the detail.
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Hameg made some really good and affordable scopes. Another recommendation right there. I agree the analogue scopes are of course clumsy when you wanna document stuff. Obviously this is where DSOs really shine.

Just for fun, my 1st scope was an ancient and very basic AEG Elograph (no, I didn't make that name up) from the late 50s -- and it uses valves! It's cute and portable, has a 1MHz (!) bandwidth (on a good day) but is incredibly rugged. Fell off my bench onto the concrete floor once. Front panel all bent and beat up. But no broken glass. After a quick panelbeating it fired right up as if nothing happened! :biggrin:
 
Keep an eye on this one as well as that Owon

www.ebay.co.uk

Hitachi VC6025 digital storage oscilloscope | eBay

<p dir="ltr" style="margin-top:0; margin-bottom:0;">Hitachi VC6025 digital storage oscilloscope.</p> <p dir="ltr" style="margin-top:0; margin-bottom:0;">This is a dual trace, 50MHz scope. It powers up and has two trace lines on screen, I couldn't say for certain if it's working correctly as I...
www.ebay.co.uk

Though I note its not fully tested
 
ethump said:
How about a Hantek 6022BE? I've found one for 40-50GBP.

I've no idea about these things (yet)... what bearing Mhz bandwidth, triggering, samples/sec etc has on what I need to use it for...
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I went through the same thing as you are now. What are the important specifications and how do they relate to my needs? In the end I ended up buying what I did as the reviews stated it is a great entry level scope. However I think it has more capability than I'll ever need to troubleshoot these old computers.

I would recommend you watch some Youtube reviews on this. From what I watched it appears it will work acceptably for troubleshooting an Apple II computer. If that is the primary (only?) reason you're buying a scope then this would suffice. If you intend to use it for more then I would recommend a stand alone unit. Watching the videos it looks as if using a mouse and a cursor to change settings would get old really quick. Also, at the price point you're talking, you could resell it and get most if not all of your money back if you feel it isn't meeting your needs and buy something else.
 
When looking for an old 'scope, I found it more fruitful to look for all scopes available to me. Then determine which ones fit my needs and which don't, rather than looking for a handful of suggested models which may be hard to find. Don't let a good scope pass you by simply because it isn't the exact model someone recommended!

I also learned quite a bit (Now forgotten) about scope ratings and features since i was looking at so many different scopes.
 
Gary C said:
Keep an eye on this one as well as that Owon

www.ebay.co.uk

Hitachi VC6025 digital storage oscilloscope | eBay

<p dir="ltr" style="margin-top:0; margin-bottom:0;">Hitachi VC6025 digital storage oscilloscope.</p> <p dir="ltr" style="margin-top:0; margin-bottom:0;">This is a dual trace, 50MHz scope. It powers up and has two trace lines on screen, I couldn't say for certain if it's working correctly as I...
www.ebay.co.uk

Though I note its not fully tested
Click to expand...
Well spotted! That's a great DSO for the (current) price. Bandwidth is ok for the intended purpose too. Grab 1 or 2 probes and you're good to go.
 
Our friend in Portland reckons the Hantek 6022 would be just about sufficient for my immediate needs. I take your point about other 'scopes being useful for other applications but at this stage, I'm not sure what that would be. I was already watching that Owon - it's sat at £100 now with a healthy number of watchers so I suspect it'll end up being more than I really want to pay... but equally, it'll probably hold it's value. The Hitachi might be a good punt so I'll keep an eye on that also.
 
retrogear said:
Did you check the pins of the character generator rom at A5 in front ? It looks like your missing one column of pixels in each character. If you leave that rom out it should beep but show solid white screen.
Make sure that speaker is good with an ohmmeter.. It's a great part of the diagnostics.

Larry G
Click to expand...
Chip looks intact and clean. Removing it does indeed result in solid white screen, but no beep.

Speaker measures 8 ohms.
 
Do you have a multimeter ? Is reset being released ? Should be 5V on the 6502 reset pin 40.
Also make sure you have -5V and +12V coming out of the power supply. Without that, all ram is dead.
The power supply connector on the motherboard can get oxidized too.
 
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ethump said:
Our friend in Portland reckons the Hantek 6022 would be just about sufficient for my immediate needs. I take your point about other 'scopes being useful for other applications but at this stage, I'm not sure what that would be. I was already watching that Owon - it's sat at £100 now with a healthy number of watchers so I suspect it'll end up being more than I really want to pay... but equally, it'll probably hold it's value. The Hitachi might be a good punt so I'll keep an eye on that also.
Click to expand...
Perfect timing.
 
retrogear said:
Do you have a multimeter ? Is reset being released ? Should be 5V on the 6502 reset pin 40.
Also make sure you have -5V and +12V coming out of the power supply. Without that, all ram is dead.
The power supply connector on the motherboard can get oxidized too.
Click to expand...

Getting 5V across pins 1 & 40 on the 6502

PSU reports correct outputs at its connector pins.

Each of the 8 RAM chips on that first lower row is getting the correct voltage on the pins 1 (-5V) ,8 (12V) & 9 (5V) with 16 as GND
 
remove all the roms except F8. You can put the chargen rom back in if you haven't already. You're correct that it shouldn't cause it to hang, I just was hoping because of the character anomaly that it
might trigger a clue. I have documented that a bad D8 rom caused a screen full of ???. With only the F8 rom installed, you should get a beep and crash to the monitor showing E002-. A bad F8 rom would
definitely show what you're seeing.
 
The other easy thing to try is setting your meter to ohms (not diode check) and measure all the address and data lines to ground for low ohms as in hundreds of ohms. Normally they should all be high K ohms.
I had a shorted 8T97 buffer read like 200 ohms on one of it's lines.
 
ethump said:
Getting 5V across pins 1 & 40 on the 6502

PSU reports correct outputs at its connector pins.

Each of the 8 RAM chips on that first lower row is getting the correct voltage on the pins 1 (-5V) ,8 (12V) & 9 (5V) with 16 as GND
Click to expand...
I am still leaning towards something wrong with the first row of RAM chips. However, without known good chips or a scope it will be difficult to rule out.

Have you had an opportunity to reseat all of the chips?
 
oldpcguy said:
I am still leaning towards something wrong with the first row of RAM chips. However, without known good chips or a scope it will be difficult to rule out.

Have you had an opportunity to reseat all of the chips?
Click to expand...

Not reseated all the chips yet, no.
Will do in the next few days.
Working on a scope or DRAM tester.
 
ethump said:
Not reseated all the chips yet, no.
Will do in the next few days.
Working on a scope or DRAM tester.
Click to expand...
IMO if you're going to be doing this on an occasional basis then I would opt for the scope over a DRAM tester.

Is this the only system you plan to troubleshoot?
 
oldpcguy said:
IMO if you're going to be doing this on an occasional basis then I would opt for the scope over a DRAM tester.

Is this the only system you plan to troubleshoot?
Click to expand...

Well.... most of my old crap works.... probably not going to be the case forever... so yes, a scope is probably in my future...!
 
ethump said:
Well.... most of my old crap works.... probably not going to be the case forever... so yes, a scope is probably in my future...!
Click to expand...
These Apple II systems are quite resilient and have held up well to the test of time. It's been my experience and observation the weak point is the memory chips. I have recently revived three Apple II Plus systems and a number of Apple Iic systems (about a dozen in total). The primary failure I have observed with them is the memory chips.

This is not to say that your issue could be something else. Especially with the condition of the ROM chip you posted. But it's where I would start and a scope is definitely a must for anyone who will be doing this type of work on a semi regular basis.

Is it possible you could post high resolution pics of the system board? What is the part number for the memory chips?
 
Struggling to upload pics of a decent res to this site.

This link is the link to all the photos to do with this A2. Though it's not working for me using a different Google account.

photos.app.goo.gl

Apple ][ project

51 new items · Album by Iain Hardcastle
photos.app.goo.gl photos.app.goo.gl

I have to head out now, if it's not working in a bit, I'll think of something else.

There's close ups of the mobo and chips toward the end.
 
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