I posted about this a while back ago but I want to jump back on the horse and try to get the 2+ working again. Here's where I stand:
1. I used an old cut up 300 watt PC power supply because my 2+ didn't have one when I got it
2. The first two rows of RAM have 8116s instead of 4116s and the 3rd row has another kind. I don't remember what they are off the top of my head but they aren't 4116s.
3. Upon stripped down boot up, all I get is a screen full of ??@@??@@. No beep, no prompt, just ??@@. If I remove all the RAM, I get all ???? (No @s).
4. All voltages on the RAM pins check OK, reset pin on the CPU is about 2.37v but I don't think it would keep the system from booting. Or will it?
5. Keyboard input does nothing. This includes CTR+(other keys)
6. The 6502 and ROMs get warm after a few minutes of being on. Not super hot, just warm as if it were working.
I think that's all. If there's anything else to check, please let me know. I have a multimeter and ocilliscope. I'm not 100% sure how to use a scope and I don't have a probe so i'm not sure if the scope will be useful.
One site said it could be either RAM, databus, or addressing bus. I know I need to get a row of working 4116s but is there anything else that might be the issue? Just to save rounds of ordering chips.
Let's get 'er going!
So what you need is a Power Supply and a Motherboard?
Steven
Yup, that'll make it work great! Lol
Have you tried lifting up and reseating all the chips?
Yep. Also sprayed them all with contact cleaning spray and sanded the pins a little to get rid of any currosion.
The "one site" was here...
might be usefull to others that want to pick up the torch to point to old thread
to show what was proposed up till now - at:
http://www.applefritter.com/?q=content/apple-boot-issues
speedyG
Finally figured out the image system! Here's the top side of the board: http://www.applefritter.com/?q=content/apple-0
Hello Streamlined Steamroller,
after all you finally posted a picture of the board....
ccongratulation,
it's a Rev.4 Mainboard.
I've uploaded the picture back with some comments and markings.
A: Check if this Chip at position C1 is really a 74LS153. You can swap this chip with
one of the chips at position E11, E12 or E13. If behaviour at
bootup does not change we may assume the chip to be correct and O.K.
B: Checkout at position B10 if pin 13 is really clean inside of the socket
and not crunched.
C: The D-row of RAM chips is mixed with 3 different typs of chips. Thats a
situation the Apple mainboard does not like. The chip at position
D10 is the slowest with only 300 milliseconds accesstime. It's also definitly
not correct typ of chip and i would recommend not to use it.
E: The 3 chips at position H3, H4 and H5 handling the adressingbus are mixed up from different manufacturers.
Not the best solution. Try to get 3 74LS367 from same manufacturer.
F: Swap out RAM chips from Row C and Row D and store them temporary on a
antistatic foam and swap RAM chips from Row E to Row C for repeating initial testing,
Use this RAMchips till Apple boots correct again or this row is replaced by 4116 chips for
testing and if replacing by 4116 chips make sure that the 8 RAM chips are from same typ,
same manufacturer and same speed !
G: Check the memory select plugs for broken or bent pins.
Perform initial testing first after points A to G have been checked or corrected.
speedyG
Gee thanks! I spent the evening working on the 2+ and unfortunately could not get it to boot. Here's what I did:
A. The chip at C1 was actually a 74153 (no LS). Not sure if this is a compatable chip but I swapped it with the 74LS153 at E12. I got the same ??@@s but sometimes when cycling the system, ]s, /s, =s, or >s would appear in almost a logical grid in amongst the ??@@s. Probably is just a coincidence but the ]s almost made me think it was trying to boot.
B. The socket at B10 had a curroded pin. I removed the chip and cleaned it along with the socket the best I could and verified I was getting conductivity with a multimeter.
C&F. I removed all the RAM and put the 3rd row (the 9016s) in the first row. Same result.
E. Miraculously, I found two other Texas Instrument 74LS367s. They had the number and date code in opposite positions from the original one on the board but Texas Instrument chips none the less. Didn't effect performance.
G. I didn't see any broken pins but I couldn't inspect them very well. No broken solder joints.
With all this, I assume I'll need to order a new set of 24 4116s and possibly three 74LS367s?
I would start first with a set of 10 x 4116
and the 3 74LS367.
4116 RAMs are usually nowadays salvaged from junkyards even if seller promises
them to be NOS. So its recommended to order 2 spares for testing. The rest of
RAM chips should only be ordered after verification, that the board boots up with 8 chips.
- otherwise you might be killing 24 working chips with a damaged board.
But i would first recommend some further "swapping tests! before order and purchase,
to hunt for change in behaviour and narrow down of problems.
If you swap a damaged chip the computer will change in its behaviour at booting up !
But to really identify a damaged chip its needed that you will have to swap only 2 chips
at a time try bootup and then swap next 2 chips repeating same procedure of test by bootup
again and watching each time if display changes significantly !
Of course this will require about 30 test cycles.... but by this procedure you can
check very many chips for theit reliability without need to order new ones.
If a swap changes display at bootup significantly then one of the 2 swapped chips is rather
sure a damaged chip and should be marked with a label.
By the procedure of swapping be sure to examine each time that the pins are really inserted correct
in the socket and did not bend a pin and slip below the chip ! In 70% of all cases such a mistake is the
cause of mainboard malfunction ! Pay also attention to orientation of the chip : all notches of the
chips point same direction toward front side at the keyboard. And while tests the keyboard shall
remain plugged to the mainboard !
At the picture below i sorted similar chips, that may be swapped by similar colors and arrows.
sincerely
speedyG
speedyG
Sorry it took a while to reply, didn't get a chance to work on the ][+ over the weekend. I swapped chips around this evning and nothing different from what i've been experiencing. I did find one 74LS139 had a broken pin. Not wanting to heat up and potentially damage the chip, I simply stuck the broken pin in the socket and made sure it made contact with the chip. Still no dice. I assume this means the RAM is most likely the issue?
One other thing, I can get brand new 4116s from www.jameco.com for about 99 cents each.
They will be correct.
Hi everyone! Sorry I haven't posted in a while, I was waiting on parts. Anywho, I replaced the first row of RAM with brand new, not NOS or salvaged, newly made 4116s (or at least I think). I also replaced all three 74LS367s next to the 6502 with Portuguese made chips by Texas Instruments. I also replaced both 74LS139s in column B. After all this, I plugged the machine in and turned on the monitor, same exact problem as before. Any more ideas?
From the schematic of the ][+, the data output pins of the DRAMs goes via 2 x 74LS174 located at B5 and B8, then via 2 x 74LS257 located at B6 and B7, then via 2 x 8T28 at H10 and H11, then arrive at the 6502.
If you want to learn more about the circuit for troubleshooting get a copy of "Understanding the Apple II" by Jim Sather.
http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Books/
Regards
GeoffB
Up till now i've only viewed the component side of the mainboard.
Can you please post a good quality picture of the solderside of the mainboard ?
Similar is valid about the keyboard.....
can you take a picture from the solderside of the keyboard and post a link ?
Do you have besides of the Multimeter other testing equipment ( oscilloscope ) ?
Otherwise we have to step back to message #9 and check for changes in booting up
while performing moves of similar chips in a "swap around" by single steps to
detect changes in bootup behaviour ( slight changes in bad display ).
Sure thing!
Solder side: http://www.applefritter.com/?q=content/apple-motherboard-solder-side
Board that connects to keyboard (keyboard interface board?): http://www.applefritter.com/?q=content/apple-keyboard-interface-card Disregard the extra green wire. I broke a pin off of the ribbon cable plug and couldn't repair it so I did kinda a brute force repair.
Bottom of keyboard itself: http://www.applefritter.com/?q=content/apple-keyboard-underside
I still have the odd feeling that the issue may lie in my power supply. Something inside me wants to say the 300 watts instead of the original 70 watts is messing with something. One day I'll try to find an original.
Will try swapping around more chips.
sorry, but that pictures are not usable....
total size of less than 100 kB is in best case "size of thumbnail"...
no chance to zoom in and inspect solderjoints...
required size must be at least 2000 x 3000 pixel.
green wire at keyboard from where to where ?
I looked at your original post, and the startup pattern seems like perhaps the ROM code is not running. It could be a bad ROM (I've had many old II+'s with bad ROMs) or some of the addressing circuitry, or even the CPU.
You really need a whole working II+ to carefully swap parts to find this unless you are good with troubleshooting with an oscilloscope. Otherwise you are just relying on luck...
Hmm... I took them with the same camera and uploaded them the same way. Will try to upload them again.
The green wire is a little hack repair I did. I broke one of the pins on the keyboard cable and I didn't have a spare so I did that.
I found a site that said it could be the data or adressing bus but you're saying it could be a ROM? The F8 ROM doesn't get as warm as the others so this could be a problem. I do have a scope (two in fact) however I do not have a probe. In addition I barely know how to use a scope.