New to Apple II & Troubleshooting

[ethump]

Hi - first, thanks all for your input - really appreciated. Very keen to get this beastie working.

Changing garbage. What I mean is that every time I power cycle it, I get a different garbage screen. To be clear, without moving any chips around, simply power cycling results in different nonsense characters on the screen just like the pictures I posted earlier.

When I was chopping and changing the DRAMs, I'd get similarly changing screens with each power cycle.

There's definitely that black crud on the legs of most of the chips. There doesn't seem to be any corrosion or other cruft on the board. I'll remove each chip, scrub the legs with some high grit sandpaper and contact cleaner.

 

[Gary C]

Good info Gary, thanks. I'll look into those bits.
I'm often in Manchester - never heard of this museum - will check it out!

Its embryonic at the moment.

We might even have a door next month !

But when its open, come on in.

 

[daver2]

My Apple disk controller had similar corrosion on a number of 74LS IC pins. Interestingly, when I removed some of the chips to clean the pins, some of the pins got left behind in the socket!

Closer inspection identified that some of the pins had been microscopically eaten through so they were not actually making contact with the IC body and were therefore floating!

I had surmised this fault with the onboard PROM (one of the address lines was stuck/floating high) and that was the pin of this IC that was left behind when I removed it!

This oxidisation is down to the manufacturing materials and process used, and is now the subject of various JEDEC Standards for that reason.

Other faults identified with certain ICs relate to the internals if the IC (e.g. bonding of the silicon die to the carrier) and can cause the IC to fail internally.

Dave

 

[oldpcguy]

Hi - first, thanks all for your input - really appreciated. Very keen to get this beastie working.

Changing garbage. What I mean is that every time I power cycle it, I get a different garbage screen. To be clear, without moving any chips around, simply power cycling results in different nonsense characters on the screen just like the pictures I posted earlier.

When I was chopping and changing the DRAMs, I'd get similarly changing screens with each power cycle.

There's definitely that black crud on the legs of most of the chips. There doesn't seem to be any corrosion or other cruft on the board. I'll remove each chip, scrub the legs with some high grit sandpaper and contact cleaner.

I've found soft pencil erasers work well for cleaning pins.

If this doesn't work then I would suggest following the other recommendations in obtaining a chip tester. Otherwise, an oscilloscope would be the next step.

 

[daver2]

I've found soft pencil erasers work well for cleaning pins.

If this doesn't work then I would suggest following the other recommendations in obtaining a chip tester. Otherwise, an oscilloscope would be the next step.

Thanks for adding that. I was going to mention that in my post this morning but completely forgot...

Keep the sandpaper for painting and decorating .

Dave

 

[ethump]

Noted.

On the subject of oscilloscopes - does anyone have any experience of those cheapy JYE tech ones? Are they good enough for goofing around with this old stuff?

JYETech 'DSO Shell' Oscilloscope DIY Kit w/Enclosure & Clip Probe by NooElec. Low Cost Digital Storage Oscilloscope with 2.4" TFT LCD. Model DSO150 (DSO 150); SKU 15001K : Amazon.co.uk: Business, Industry & Science

Buy JYETech 'DSO Shell' Oscilloscope DIY Kit w/Enclosure & Clip Probe by NooElec. Low Cost Digital Storage Oscilloscope with 2.4" TFT LCD. Model DSO150 (DSO 150); SKU 15001K at Amazon UK. Free delivery on eligible orders.

www.amazon.co.uk

cheers

 

[VERAULT]

You get what you pay for.. in that case you get about $30.00 lighter on your bank statement.

 

[daver2]

You can measure up to 128 kHz (or so with a following wind) with these.

They have a use - but not much.

I have one that I can stick in my back pocket and I occasionally bring it out to look at the voltage levels and edges on serial signals. You can check some signals - but don't expect much...

Dave

 

[oldpcguy]

Noted.

On the subject of oscilloscopes - does anyone have any experience of those cheapy JYE tech ones? Are they good enough for goofing around with this old stuff?

JYETech 'DSO Shell' Oscilloscope DIY Kit w/Enclosure & Clip Probe by NooElec. Low Cost Digital Storage Oscilloscope with 2.4" TFT LCD. Model DSO150 (DSO 150); SKU 15001K : Amazon.co.uk: Business, Industry & Science

Buy JYETech 'DSO Shell' Oscilloscope DIY Kit w/Enclosure & Clip Probe by NooElec. Low Cost Digital Storage Oscilloscope with 2.4" TFT LCD. Model DSO150 (DSO 150); SKU 15001K at Amazon UK. Free delivery on eligible orders.

www.amazon.co.uk

cheers

I don't have any experience with the lower cost DSOs but I imagine for a one time use it might be worth giving it a shot. If it doesn't work you can always return it.

That said if you're planning on goofing around with this old stuff I would recommend buying a better quality oscilloscope. I ended up buying a Rigol DS1054Z. It received great reviews for an entry level DSO and I'm very pleased with it.

 

[Gary C]

If your budget is limited I would really recommend an old scope from Ebay.

Something like a Phillips, Gould or Hameg.

Dual trace with external trigger. 20Mhz or above

They take up lots of space on the bench, but you will be able to get a quality device for not much more than that fairly useless device.

But remember, its a tool and don't always believe what its telling you.

AND, dont use it like a volt meter, the earthed side of the probe is normally connected to mains earth so if you try to measure a voltage across say a resistor in a PSU, you might just connect a part straight to earth

Then when your hooked, you can save for a quality DSO and marvel at how you ever managed without such a light and small footprint device.

Mind you, this https://www.ebay.co.uk/itm/234403672657?hash=item36938c3251:g:~ysAAOSweXRh-o8M would do almost everything you need (it does miss the external trigger, but its not essential)

 

[ethump]

Gary - yes I saw that scope and added it to my watch list. I shall keep an eye on it. I'd expect it to shift significantly higher than the GBP30 it's sat at now though!

Those Rigol's are GBP 3-400!

A friend recommended a PicoScope .... might jump on one of those if that Owon one goes pricey.

 

[oldpcguy]

Gary - yes I saw that scope and added it to my watch list. I shall keep an eye on it. I'd expect it to shift significantly higher than the GBP30 it's sat at now though!

Those Rigol's are GBP 3-400!

A friend recommended a PicoScope .... might jump on one of those if that Owon one goes pricey.

They are but well worth it if you plan to do this on a regular basis. I didn't get the impression that you were which is why I seconded the recommendation to go with a low cost chip tester instead. Never crossed my mind to suggest a used scope so I'm glad to see Gary did.

 

[GanjaTron]

Just saw this post today -- interesting discussion.

I have a DSO-shell and it's basically a toy for occasional use. Its bandwidth and voltage range is pathetic, and it's frustratingly fiddly to use. You won't get much joy out of it in the long run.

I have a two old Philips PM scopes for real work, and they're well documented and reasonably easy to calibrate. The big advantage of these scopes is that you don't need them on your bench -- they can be stood upright on the floor next to you if space is tight. Very convenient. One thing to look out for is exploding RIFA caps in these scopes.

Speaking of RIFAs... there are two in the Apple ][ PSU as well. I recommend replacing these if you haven't already done so.

Looking at the faults on your Apple ][, I'd also suspect the ROMs. The issue may be in the chips themselves, not the corroded pins. I've seen mask programmed ROMs fail in my Tek and KIM. I believe these were Mosteks (MK3600 or some such). I think this depends on the manufacturer and the process used. Or perhaps the addressing logic is knackered. But you'll definitely need a scope to check that.

Btw, didn't René say "Allo Allo"?

--Roland

 

[retrogear]

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

 

[GanjaTron]

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.

I noticed that too. But would the character gen. cause it to hang?

 

[ethump]

Finally out of 10-post jail so I can annoy you all with greater frequency!

Roland, yes, all caps in the PSU have been replaced, including the X2 RIFAs.

Alright, I'll ditch the idea of those shonky 'scopes.

Rene did indeed say "Allo Allo dis eez Nightawk" but I guess I was referring to PC Plod saying 'ello 'ello when he's discovered something potentially critical to an investigation

I do have a good collection of old crap but apart from the Acorn stuff, I doubt much of it is fixable-if-it-goes-wrong on a hobbyist level. So I'm 50/50 on dropping decent cash on a 'scope. I'd be happy to spend GBP50-100ish?

Larry I'll check your suggestion and report back!

 

[GanjaTron]

Finally out of 10-post jail so I can annoy you all with greater frequency!

Yay! Go right ahead. My Apple ]['s (original and clones) all work, which is boring. I wanna see a resurrection for a change.

Roland, yes, all caps in the PSU have been replaced, including the X2 RIFAs.

Good on ya! Gotta take care of those ticking bombs...

Alright, I'll ditch the idea of those shonky 'scopes.

You can have my DSO shell, but it won't even be worth the postage.

Rene did indeed say "Allo Allo dis eez Nightawk" but I guess I was referring to PC Plod saying 'ello 'ello when he's discovered something potentially critical to an investigation

Ah ok. Must've missed Plod. I bet he never said "Leessen very carefullee, I shell sey zeez only wance"

I do have a good collection of old crap but apart from the Acorn stuff, I doubt much of it is fixable-if-it-goes-wrong on a hobbyist level. So I'm 50/50 on dropping decent cash on a 'scope. I'd be happy to spend GBP50-100ish?

50-100 quid would buy you a pretty decent 2nd hand scope. Unless you plan on doing something fancy you could also settle for a good old analogue jobby, like those Philips PMs I mentioned. 2-4 channels with 150-250 MHz bandwidth should be good for starters. I'd stay away from no-name stuff in case you need to calibrate, as service manuals may not be available.

Other good ones are of course HP and Tek, but you tend to pay a premium for those. I have two very flexible mainframe Teks from the early 70s that take plug-ins. These are great to have on the bench, but you don't wanna lug these boat anchors around.

Finally, my only DSO is an early 9300 Series LeCroy, which is fantastic and has a really good UI (and that's coming from a non-DSO guy). However, you'd be hard pressed to find one under £100.

No home should be without a scope. I always have one within arm's reach.
When I lived in the UK, I spent a lot of time checking out gear on gumtree. Might be your best bet.

Good luck and sorry for getting OT.

--Roland

 

[ethump]

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...

 

[GanjaTron]

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...

I've never hard of Hantek, but 20MHz is pretty much on the low end; that's what my older Philips from the early 70s manages. The thing to note is that the scope's bandwidth can vary in practice. Some manufacturers (notably the more reputable ones like HP and Tek) typically factor in a tolerance, so the scope's response won't degrade immediately as you approach its designed bandwidth. YMMV with other brands.

It's also important to note that your effective bandwidth ultimately depends on the bandwidth of your probe; there is no point in hooking up a cheap probe to a high-end scope as you won't benefit from the latter's performance; the probe will already reduce the bandwidth in this case. Note that brand name probes can be very expensive, but you can save by getting a decent quality one from a 3rd party manufacturer. I use a Testec 150MHz probe with sells for around 20€: https://www.reichelt.de/modulartast...estec-lf-312-p32416.html?&trstct=pos_10&nbc=1

This probe can also divide the input voltage by 10; this is very important to prevent blowing your scope's input amp (or if you're lucky, a hard to replace fuse) with excessive voltages. However, only proprietary probes will transmit this factor to the scope so it can adjust the readout accordingly (AFAIK there's no standard for this). Personally I don't care, I do the maths myself.

As a bare minimum, I would look for a scope/probe combo around the 50-100 MHz bandwidth. This may not be an immediate requirement for the task at hand, but you'll be happy if you do need it one day. Scopes are pretty much your universal troubleshooting tool when the DMM no longer cuts it.

--Roland

 

[Gary C]

I note that that Hantek can only manage 250 million samples per second (for comparison the Owon linked above is doing 1 billion samples per second), so would only sample a 16Mhz wave about 15 times, which is enough to show you its there but might miss some detail. Not sure if it can show real time ?, I would have though the USB could be a bottleneck to displaying in real time ?

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.

I like hard controls too, and often I am using the laptop for drawings etc so a desktop scope is important.

And I agree with the 'universal' tool for computer diagnostics, I use mine for almost everything bar belling though connections.

Just been diagnosing an Osborne 1 disk drive. The write signal is not getting through the differential amp and without a scope, I would not be able to check it with a logic probe.