Hi everyone! I'm having some issues with a recently acquired Apple 2 plus. When I boot it up, all I get is a screen full of ??@@??@@??@@. I removed all the expansion cards, no luck. I tried reseating all the ROMs and spraying their sockets with contact cleaning spray, still nothing. I tried wiggling some of the chips in their sockets, sone times I will get some other random garbage in the ??@@s. I checked with a picture online and all the ROMs are in the right places. Does anyone know what might be the issue?
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Oops! Forgot to mention the keyboard has no effect and I don't get a beep upon startup.
The power supply is probably the easiest thing to check before diving deeper. If you have a spare known good Apple ][ or //e supply you can do a transplant just to check and see if it makes a difference, or you could check the voltages under load to see if anything is amiss using a multimeter.
If you wiggle the sockets and get different garbage that may point towards some loose connections or short circuits on the motherboard, you could try reflowing solder on each IC socket (with the IC removed, to stop potential heat damage).
Actually, my 2+ didn't come with a PSU so I cut up an old 300 watt PC power supply to replace it for now. Shorted the power ok wire to the common and the hard power switch controls the entire PSU. I checked my connections many many many times before turning the unit on. This is my first Apple 2 of any kind and the only other power supply on ebay going for $35 to $55, this is what I went with.
HI Ste,
Unsurprisingly there isn't one single issue which causes this, though at least you know that the video circuitry is working.
Anything from a cracked trace to bad socket to bad power to bad RAM to a bad LS chip via a bad ROM to a bad 555 timer to a bad CPU can be a problem.
Simple checks first - power and RESET. How much do you know about 6502 based systems? 4116 DRAMs? Reading schematics?
I've just been through this with 3 other machines so let us know where you're at with troubleshooting skills.
Cheers
W
I'm pretty new to the wonderful world of 6502 systems (my only other 6502 machine being a Commodore SX64) but I know the basic operating principals of a computer and can read schematics. Another hobby of mine is antique tube radio repair so schematic reading isn't an issue. I like to believe I can troubleshoot pretty well if I know what each part of the machine does.
Wait a minute, Witchy, you replied to my post on VCF! I'm 6502Fan over there.
Ah, hello
I've just posted a reply over there. I wonder if board etiquette means I should also post it here...
W
I would... For Continuity...
MarkO
OK, edited slightly because context:
RESET on 6502 pin 40 should always be 5V while the machine's running. Clock on pin 37 (phi2) should be around 2V.
Voltage-wise check for:
5V pin 8 6502
5V pin 24 ROMs
5V pin 1 4116
12V pin 8 4116
-5V pin 9 4116
Next I'd remove all the RAM and processor to see if the display changes. With a multimeter set for continuity check that pin 2 (DI) on each *column* of RAM sockets is connected together (eg C10, D10, E10), also pin 14 (DO). Then check the address bus and CAS/RAS/WR line on each *row* (eg C3 - C10 pins 3-7 and 10-15). Google for '4116 pinout' to reference. Download the best reference guide for the ][+ from here. All the schematics you need are at the end. Another good resource is Mike Willegal's troubleshooting page here.
At its most basic you need a boot ROM (known as the $F8 autostart ROM) in F3 and Row C of RAM populated with 8 fully working chips.
W
Handy info, thank you. For some of us that haven't yet invested in an oscilloscope (I'm slowly wearing down), a multimeter is the only tool we have.
Hi,
Even with a meter you should be able to check the
Reset line - Pin 40 on the 6502 CPU.
Attach the common lead of your meter to ground
and the positive lead of your meter to pin 40.
Press the RESET or Ctrl with RESET key on
your keyboard and the voltage reading on you
meter should dip towards zero.
If not the system isn't reseting.
Check the transistor and resistor around
location A13 along with the 555 timer IC.
I had issue where the 2.2 M resistor was
actually open preventing a Power on RESET.
Those aren't Mike's troubleshooting notes. He's not the author. They're Apple Service repair notes that are on his site because I typed them from photocopies and gave it to him many years ago.
Thanks for doing that, it's a useful addition to anyone's 'fix it' collection. Perhaps the notes should state the origin since I first happened across them from a search, not via Mike's site directly.
W
Sorry I haven't been replying lately. I'll check more processor voltages. Is there a way to determine if a chip is good or not with an ohm meter? Say if I were to check the continuity of the + input to the - output?
I checked everything you said and everything checks OK. I looked at the troubleshooting guide and my problem wasn't listed. I tried a few things in the guide that seemed something like my problem but no dice. I got curious and checked the output of the 555 timer in A13 or so and it was about 0.2v to 0.5v while the 555 timer in B3 had an output of 2v. I swapped them and the same thing happened. Not sure if this is the problem but it might be. Any more ideas?
I'm also wondering if the problem lies with my makeshift power supply. Again, i'm using a cut up 300 watt PC power supply. The original power supply was 70 watts. Could the problem lie here?
That power supply should be more than enough even with a full suite of cards. If the voltages under load check out then you can rule it out as an issue.
Each rail on the Apple II PSU has different amperage requirements however, it might be worth double checking these to make sure that your PC PSU meets these, just in case. I remember the -5v requirement being particularly tricky for some PSUs to match.
I got a little curious about the RAM because the first row was regular plastic coated ICs while the other two were not. The other 2 rows were 8116. Apparently someone was trying to expand the memory. I removed all those and finally got a change on the screen! Instead of @@?? I get all ????. I decided to remove the rest of the RAM and got no change. I then removed the ROMs and processor. Still no change. I then began to remove random chips. Most had no effect and the ones that did were video related. Even when I removed the 555 timer for the clock I got no change. Any more ideas?
Repost from my post on VCF:
Pin 3 on A12 measured open to ground. I changed the 3904 and then it went down to a few kOhms. The reset pin is now getting 1v and jumps up to 1.26v when I push the reset button. I'm guessing the A12 is bad?
I made a video of the problem back when it was ??@@ https://youtu.be/XEd5UCwrlJc
Hello...
interesting when i stay off just a few weeks....none of the members
that have joined this platform for longer timer ever thoght about mentioning this page:
http://www.appleii-box.de/D06_resurection.htm
?
Instead if digging around for a possible "lucky hit"
ever anybody thought about searching with system ?
sincerely
speedyG
That did certainly narrow down the problem, it seems I have a problem with the Databus. The only question is, which IC? Is there a way to determine which IC is the problem without guess and checking by replacing ICs? Would a scope come in handy perhaps?
This page was made because most readers don't have a scope and
therefor the page offered solutions without a scope.
If you have a scope of course it's even faster to solve the problem.
At the beginning of the page there is a map of the chips and the colors
indicate the function.
The chips related from D0 to D7 and the RAM are indicated in light red shade.
I guess that you have downloaded the related books with the circuitplans from:
http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Books/W.%20Gayler%20-%20The%20Apple%20II%20Circuit%20Description.pdf
view the lastpages...
and
http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Books/Sams%20ComputerFacts%20-%20Apple%20II,%20II%20Plus.pdf
as well as:
http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Books/Chilton%20-%20How%20To%20repair%20and%20maintain%20your%20Apple%20Computer.pdf
I've recommended this links dozends of times in this platform in former postings....
and i remind to the statement:
for testing it's recommended to test with only first bank of RAM chips present !
Reread that part of the page and the tips about selection of the RAM chips ( timing / manufacturer )....
When the computer starts correct you may test second row of chips in first bank,
then third set of chips in first bank.
When then chips are tested completely you may first add second row and test again
and then third row and test again and then languagecard and test again.
The reason:
If a chip at Dataline D3 for examle is dead it will kill operation at complete dataline...
you would not be able to determine which chip kills the line...
but if you check the chips row by row in the first line you will surely find the damaged chip !
In the first book as well as the second the pinouts of the chips are indicated in the plans
by pinnumbers.... so you know where to measure with the scope.
Hunt for chips with "frozen" pins "without action" !
speedyG
The site said there is something wrong with the Databus or addressingbus. Would it be wise to go ahead and order parts and just replace the 5 ICs next to the 6502 in row H?
Hello,
why don't you just follow up the instructions ???
there is reason that this instructions have been written !
One reason is to save time and money by ordering wrong parts !
Seems i even should add further explenations to the page to avoid such suggestions like the one here....
Strip down the system to one row of RAM.
Then the trouble can be narrowed down to D0, D1, D2, D3, .... D7 !
If it's not one of the chips - then next step would be to examine 74LS174 at location B5 or B8 !
in the first row only adressinglines from A0 to A7 are involved.
By experience i can tell that the chips in row H are in less than 5 % of repairs the source of trouble !
So by the explained procedure by stripping down to 16 kB the possible sources of trouble are limited
to a bunch of 10 to 12 chips ! And for 8 of the chips you have still 16 other chips present to replace
damaged chips without ordering new chips !
Remember one thing : A damaged RAM chip can kill the communication of a dataline or adressingline
by shortcutting it !
Then - when the system boots up normal with that first row - it's recommended to check chips for later
second row and third row but testing them in Rom 1 where you then really know that the chips of the
databus and lower part of the adressingbus are O.K. - so then malfunction is for sure dependent to
the tested RAM chips themselves and you can sort out damaged ones !
After that procedure of testing chips in row 1 - you then may add up second row and test it again.
If then a problem rises it's limited to 4 or 5 possible chips that are responsible for selection
of the RAM rows ( RAM banks )
- then adding third row of chips and testing third row!
By that you finally will have sorted out that chips, that really must be replaced !
And at that point you can boot up with a diskinterface with a dealers disk and test the system tough
and after adding up the languagecard you then also may test the languagecard with the dealers disk !
If you prefer to follow your own suggestion you will end up with 3 or 4 cycles of ordering chips
( and most of them without even need for replacemt and waisting weeks of time testing without success
because your just guessing around instead of really locating the problems !
But if you know better than a guy, who has repaired more then 150 Apple II computers....
then leap ahead to "TRY and ERROR" and kick out your money!
Omg, I feel stupid now. I was rereading the CommandCompare site and I've been stripping the wrong rows of RAM. I was stripping the machine down and leaving the 3rd row of RAM which is apparently the closest to the 6502. My logic said the third was the first. Will try again. I never was good at reading instructions the right way.
Just for the record, I read through the command compare site but I am not going to read through 200+ pages of the Sam's manual until i've tried absolutely everything.
Sorry about causing frustration, will look at the site more closely.
SAMs Computerfacts is only 66 pages.....
it's just mentioned, because you mentioned that you can use an oscillscope and it contains
pictures of the expected measurings with oscilloscope for diagnostic purposes.....!
and the Apple II circuit desription from Winston Gaylor ( and that one really has more than 200 pages )
was mentioned because it has detailed explenations of the functions inside of the Apple II.....
and it contains at the rear part circuitplans that are easier to handle than those in SAMs Computer facts,
because there the diagrams split the complex plans to function blocks.....
It's recommended to have a reference on shelf if and trouble rises and you want to perform research on your own
by understanding how the Apple works.....
and yes at my page it is explained that the first row of RAM is at the C-row and that at the E-row is the 3rd row
( first picture on the page - comments in the picture ! ).
I spent a little more time with the apple. I left the real row 1 with RAM and got the same thing, ??@@. I took another look at the directions on the CommandCompare site and here is what it said under the image of my problem:
This kind of screen or similar black/white screen is displayed in later bootup stage if adressing line or dataline is not working. This kind of mistake might be related to a single RAM chip - but rather more it's related to the chips controlling the data- or adressing busses ! In such case it's in most cases related to the Databus and not the adressingbus.
I then looked at parts 3 and 4 (databus and addressing bus) and this is what they said:
3)
In case of adressing port malfunction one or more of the 3 adressing port chips 8T97 at position H3, H4 or H5 is responsible for the trouble.
The easiest solution would be to swap a spare similar 8T97 chip step by step through all 3 positions and try by that to identify the damaged chip.
Depending to the version of mainboard in later mainboard versions instead of the 8T97 the chips have been replaced by 74LS367 chips.
In such a case of course the replacement chip also should be a 74LS367.
4)
In case of trouble with the databus there are 4 sources of trouble possible:
a) one of the databus buffering chips 74LS174 at location B5 or B8 might be damaged and must be replaced.
b) one of the databus from RAM to videosection chips 74LS194 at location B4 or B9 is damaged and must be replaced.
c) depending to the version of mainboard you have at the right side from the CPU ( away from the side heading to the power supply )
is either one chip labeled as 74LS244 at position H10 or 2 chips labeled 8T28 at position H10 and H11 might be damaged and
by swapping the responsible chip with a spare chip of the exactly same typ might solve the problem.
Basically, all it says to do is swap chips with a known good one, however; I do not own ANY replacement parts at the moment. I think I might simply order all the parts it says could be at fault and replace them just to be done with this project. Each chip is only $0.50 to $1.00 each on jameco.com after all.
One more thing, all the RAM was replaced in my machine at one point. RA03 had 9016s (I think, can't remember their number off the top of my head) and RA01 and RA02 had 8116s which I found out are supposedly able to substitute for a 4116. Is there any issue using these? Are they generally more reliable than 4116s or should they go?
Then we are for sure back again at the RAM chips.
Both 8116 and 9016 are in many cases a real problem !
It would be quite useful if you would have posted pictures of the mainboard
like done by other members in earlier postings related to that kind of topic !
or here: http://www.applefritter.com/?q=content/apple-2-bringing-back-life
You have not named up till now which manufacturers have made the RAM !
Neither data about the speed ???
It is known that several manufacturers have made 8116 RAM chips or 9016 RAM chips as 5 Volt only versions !
And some of then don't work in Apple Mainboards because Apple Mainboards expect 4116 chips with
supply of +5 Volt ( pin 9 ), - 5 Volt ( pin 1 ) and + 12 Volt ( pin 8 ) GND ( pin 16 ) !
( See page 202 of Apple II Circuit Description - W.D.Gaylor )
Yes, I should have mentioned it earlier, me being me again. Not sure about the manufacturer off the top of my head, will check later today. I believe the 9016s are stamped with an Apple logo but the 8116s, I can't remember. Will have to check again.
Uploading images is a hassle from my phone but if you must, I can try and upload one. First post, first Apple computer, I know nothing about what normally is and is not good, regular forum posting procedures, etc.
Someone told me to measure the voltages on the RAM before, they all measured perfect.
With the wrong RAM in mind, should I just order 24 new 4116s?
First upload pictures for diagnostic...
then i will recommend next steps...
tossing money out of the window by ordering unneeded chips won't get the Apple up faster....
use more time about how research and how to make good pictures
(good lighting good focus good resulution - how to upload - where to upload )
there have been several threads related to that topics
for research use the "search" field in upper right corner of the page...
If the system also had languagecard also make picture from that card...
speedyG
So many projects, so distracted! Sorry it has been a while. Anywho, I made a video of the problem. The board is show in the video. https://www.youtube.com/watch?v=XEd5UCwrlJc
Hi,
nice but useless video......
why ?
1. its that "parkinson-like" that nobody can view calm the chips....
2. no chance to zoom in for details
3. parts of the mainboard even stay "invisible" - are not displayed...
the only thing that can be stated from the video:
it seems to be a rev.4 mainboard with Applesoft Rom set.
I mentioned in posting #27 a thread that displays the kind of pictures requested
for diagnostic....
i get the impression that I'm talking some brazilian native dialect
upfront of the Wailing Wall in Jerusalem....
I ask - but i never get the expected response to my inquiries.....
maybe someone else will take over the torch.....
maybe another person is able to handle such kind of communication better
than me ..... it's wasting my time .....
remembers me to a kind of roleplaying game in the 80's:
lets go 3 steps west...
answer: why not go 4 steps south....
- is it needed to explain that that field is occupied
by a ditch filled with killing zombies ? LOL
I can't handle that kind of communication and i'm beyond that age to start learning it...
sincerely
speedyG
Hi, Just FYI
I've just had that issue on my Europlus, gone crazy trying to guess what was going wrong, checking every IC changing and RAM/ROM, scope measurements,voltages ... ect
I was going to give up and as last resource I changed the 6502 Turned on the computer and bang . it started working back...
Regards.