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Hello all. I am a newcomer to the board. I recently purchased an Apple II Plus from eBay. Aside from a 16K expansion card, it is a bare system. No monitor, no disk drive or controller, no other expansion cards. Just the computer itself (I've separately purchased a disk drive and controller, still waiting for them to arrive). However, I know that the computer will still boot into the BASIC prompt even if no disk drive is attached, so I decided to play around with it anyway.
However, while doing so, I noticed some odd glitches that I'm fairly sure shouldn't be happening. Keep in mind that 95% of what I know about the Apple II Plus is based off 20 year old childhood memories, so my troubleshooting expertise when it comes to this old system is fairly nonexistent. However, I did try a few different things that I was readily able to recall from memory, and came up with the following symptoms:
1. Attempting to use the LIST command almost always kicks it into the program monitor at address E851, but sometimes instead it returns a divide by zero error, then freezes. The only exception to this problem is if no program code exists in memory, in which case LIST just displays a blank line and returns to the BASIC prompt, as it is supposed to do.
2. Attempting to assign a variable (For example, setting X to equal 10) kicks it into the program monitor at address E916.
3. Attempting to run the following invalid one-line program:
10 GOTO 20
Returns "UNDEF'D STATEMENT ERROR IN" with no line number given for the error, then immediately after kicks it into the program monitor at address E851
4. Attempting any math function (1+1, 9*64, 3/0, etc.) kicks it into the program monitor at address E916.
On a whim, I did a CALL-151 to enter the program monitor, dropped it down to address 0000, then did a sort of "poor man's" memory read test by holding Rept+Return, letting it read and scroll all the way through to FFFF. Whenever it would glitch, I manually went back through and stepped it one address at a time until locating the exact address that caused the glitch. These are the results I got, the addresses that caused problems and what they did:
C050 Random patterns/text/colors on screen
C080 Hard freeze
C083 Hard freeze
C084 Hard freeze
C087 Hard freeze
C088 Hard freeze
The glitch caused at C050 could be cleared by doing Ctrl+Reset. The rest were hard freezes that required the power to be turned off and back on.
Admittedly, these may be normal, and my lack of in-depth knowledge of the Apple II may make me think it's a problem. However, there is undeniably something wrong with this computer, and this is all I was able to come up with using my limited knowledge. Until I receive the disk drive and controller card, the diagnostics and tests I am able to run are quite limited.
As previously mentioned, the computer did come with a 16K expansion card. However, the problems persist even with the card removed.
So, I felt it necessary to turn to the experts here for assistance. Childhood memories that consist almost entirely of just using the system to play games really isn't enough for me to solve this problem on my own. I appreciate any assistance.
This is expected behavior. The $C0 page is all I/O locations, not RAM, so you're accessing soft-switches and things.
Here's a little memory map for you:
$0000 - $00ff : zero page
$0100 - $01ff : stack
$0200 - $02ff : input buffer
$0300 - $03ff : free RAM, but DOS usually uses the high end
$0400 - $07ff : text page 1 (or graphics)
$0800 - $0bff : text page 2 (or graphics)
$0c00 - $1fff : free RAM
$2000 - $3fff : hi-res gfx page 1
$4000 - $5fff : hi-res gfx page 2
$6000 - $bfff : free RAM
$c000 - $cfff : I/O
$d000 - $ffff : ROM
So in other words, anything above $c000 is not RAM, unless you're using the Language Card, and you have the ROM address space switched out.
I relayed your message to comp.sys.apple2, and I received the following response from Michael J. Mahon:
You're right--something is amiss.
High on the hit parade is memory. You might also try reseating all the
chips to clear oxide from contacts.
The 16K card provides spare DRAMs to substitute on the main board, which
can help in troubleshooting. A RAM test would be a good start, but if
page zero is bad, it probably won't run--and unless you have a cassette
version, a lot of the machine needs to work for DOS to run.
I'm sure that you replaced the DRAM chip when you removed the 16K card's
"flying lead"...
Also reseat the ROM chips and verify that they are in the correct
sockets.
You can remove the upper two banks of DRAM, creating a 16KB system
which should pass all your tests. DRAM chips can be swapped in the
low bank, and if symptoms don't change, that DRAM is probably eliminated
as a source of the problem.
Good luck in isolating the problem.
Well, I tried swapping the RAM chips one at a time with a chip from the 16K expansion, no luck. I also removed and reseated the ROM chips, again with no luck. As for whether they're in the correct sockets or not, I'll need to research that, I'm not familiar with that info right off the top of my head.
I now have a disk drive and controller card I can use with the system, so that should at least provide me a means of doing a more thorough diagnosis...provided I can locate or create a diagnostic disk, that is. As it is right now, the only disk I have is a DOS 3.3 System Master, and it won't even boot from it. It gets as far as showing the DOS 3.3 title screen, then immediately either crashes into the program monitor at address BBB8, or displays a bunch of random error messages, and freezes. For example, here is exactly what it's showing on the screen right now:
DOS VERSION 3.3 08/25/80
APPLE II PLUS OR ROMCARD SYSTEM MASTER
?SYNTAX ERROR IN
?DIVISION BY ZERO ERROR IN 000tu0tvs
?DIVISION BY ZERO ERROR IN
Then hard freeze. Yes, it's showing lower-case letters, which I didn't think was possible on the II Plus. So, something is definitely screwy here.
FYI, I currently have the 16K card removed, but the same thing still happens even with it installed. The white socket where the expansion card plugs in has been filled with a chip from it, so all 24 sockets on the board are filled.
If it behaves ok executing monitor instructions as it seems , might be AppleSoft roms?. Does it modify memory locations uniquely ? - addressing problem ?
(Updated after some more tinkering, see bottom)
Apologies for letting this thread lie idle for so long, got busy with the holidays and stuff.
Anyway, I've done a little bit more troubleshooting. I removed all except for the lowest 16K of memory and repeated my tests (Except for the stuff in the monitor, I understand now that was normal behavior for reading the C050 range). The problems persisted.
I then swapped out the remaining bank with one of the removed banks, so the system still had 16K but with different memory chips. Still, the problems persisted.
With the full 48K installed, I'm able to intermittently get the DOS 3.3 disk to somewhat boot. Most of the time it crashes into the monitor, but every now and then it will instead crash to the Applesoft prompt. From this point, all disk-related commands mostly work (LOAD, SAVE, CATALOG, etc. They execute, but sometimes crash to the monitor after completing), but attempting to RUN or LIST any programs loaded from the disk causes random error messages similar to my earlier testing. Until I am able to make or acquire a proper diagnostic disk, the only disk I have for testing is the DOS 3.3 System Master
Again, the problems persist regardless of whether the language card is installed or not. Same with the Disk II controller, inserted or removed doesn't affect the problem.
Admittedly, my extremely limited knowledge of the Apple II line is still limiting my troubleshooting skills, so I can't think of anything else software-wise to attempt. I'm thinking my next step should be to try replacing the ROMs. The question is...which ones should I replace? Or, should I just replace them all? I've seen full Applesoft ROM sets periodically pop up on eBay for around $60, but there's always uncertainty with how well used pulls work, and for all I know I could end up with a set in worse condition than the ones I have now.
I did find a place that sells them burned on new EPROMs with pin adapters (ReactiveMicro.com), but at $15 each, it would be pretty pricey to replace them all (I don't have the equipment or knowledge to burn my own EPROMs). However, this would give me an opportunity to purchase and replace only the specific ROM chips that are faulty, which could help limit the necessary expense to repair the system. But again, the question remains of figuring out specifically which chips are bad (I don't have access to another Apple II Plus to try swapping parts with).
Any other thoughts?
====================
UPDATE: It appears these problems are limited only to non-binary programs. I was able to successfully BRUN the "MASTER CREATE" and "FID" programs on the DOS 3.3 disk with no errors.
====================
UPDATE 2: The more I play with it, the more I learn. Since the DOS 3.3 disk crashes during boot, it never manages to make it to the point where it loads Integer BASIC onto the language card. However, I found out how to manually do this myself. Once it is loaded, Integer BASIC programs run perfectly fine with no errors.
It's almost certain to me now that one or more of the Applesoft ROMs are FUBAR'd. The question still remains though...which ones should I replace, if not all of them?
====================
UPDATE 3: I've done a little more reviewing of my troubleshooting notes, and a little more research online. A majority of the time it crashes into the monitor, it lands at an address in the E8XX-E9XX range. So, on a hunch, I am going to try replacing the E8 ROM (Ordering it from Reactive).
In the meantime, while I wait for the replacement to arrive, any other thoughts on stuff I should check or try to see if any of the other ROM chips need replacing? Apologies if I'm asking questions that should be common knowledge on here, as I've said many times over, a majority of my Apple II knowledge is based off of 20+ year old childhood memories that involved mainly using it to play games 95% of the time. I greatly appreciate your patience and assistance with this though.
Hello,
First, I suggest you try this simple 48K RAM test (thanks to Jim Sather and his precious book "Understanding the Apple II") :
1. Go to the monitor (CALL -151)
2. Type in the following code (don't forget to add a space after 34:14 before pressing Return).
C050 C053 C054 C057 N 265:FF N 266<265.BFFEM 266<265.BFFEV 265:0 N 266<265.BFFEM 266<265.BFFEV 34:14 (Return)
The Apple II will go to HGR mode and display white and dark graphic screen along with question marks and inverse @ characters at the bottom of the screen.
If some RAM chips are bad, faulty addresses will be printed on the bottom of the screen.
Just tell me what does this produce.
When executing the code you provided, the screen slowly alternates back and forth between the following two screens about once every five seconds. Apologies for the bad image quality, these pictures were taken with my cell phone:
Solid white in the upper portion, with four rows of white squares below. No other characters/text/etc. is displayed on this screen.
Solid black in the upper portion, with four rows of inverse @ characters below. No other text is displayed on this screen.
I am assuming this means the test has passed, correct?
BTW, thank you for this code! It may come in handy in the future.
It quits back to the monitor asterisk prompt after one pass of white+squares, one pass of black+inverse '@' signs, right? It shouldn't continuously cycle.
No, it doesn't quit back to the monitor, it just keeps going until I do Ctrl+Reset to restart the computer. It never displays any memory addresses or other text while doing this though. No question marks appear whatsoever during the test. I also tried it again with the language card removed, same results.
For what it's worth, it does the same thing when I try this on my Apple IIc, continuously cycles back and forth between those two screens until I do Ctrl+Reset. I know for a fact that there's nothing wrong with RAM or ROM on the IIc, but also admit that the test could be "failing" on the IIc because it has more than the 48K the test was designed for.
I only tried it on emulators, but both KEGS and AppleWin only go through one cycle each then end.
David, you forget the space after 34:14. This test only ends when RESET is pressed. It's an infinite loop.
Well, now we now for sure that the RAM chips are good.
To test the ROM chips, you can transfer the II+ diagnostic disk by using ADT.
Then, boot the disk and choose the Motherboard ROM TEST option.
See ya.
Yep, you're right. I wasn't sure what you meant by that when you first wrote it, or why it would be significant.
Well, another update.
I was able to create a diagnostic disk using ADTPro, and ran it on the system. As suspected, it reported that the E8 ROM is bad.
Now, here's the kicker...I ordered a replacement E8 ROM from Reactive on a hunch before I even had the disk made. So, I put it in and re-ran the test.
HOWEVER...same result. With the replacement from Reactive installed, the test is still saying the E8 ROM is bad.
Now, obviously I cannot rule out the possibility of the motherboard itself being bad...and I honestly mean no ill will towards Reactive, but it needs to be said that the replacement E8 ROM I received from them was quite scratched up and appeared to have been used. So, unfortunately I cannot rule out the possibility that the ROM I received from Reactive is also faulty.
So...anyone know of another source of Applesoft E8s other than Reactive or eBay? Also, in the meantime while I search for another replacement ROM, is there anything else I can check on the motherboard itself that may be bad?
Thank you all for your patience while I continue trying to figure this out.
Hello,
You can check that your Apple doesn't have an addressing issue :
1. Go to the monitor : CALL-151
2. At the * prompt, type : E800.E8B7
It will display the starting hexadecimal values at E800. You can check them with the result of an Apple II+ emulator like AppleWin. Here is a starter.
If the values are totally different, this is almost an addressing issue.
Using AppleWin 1.19.3 for comparison, I tried this with both E8 ROMs I have, and got the following results:
Using the E8 the system came with, most of the values are the same, but every couple of lines or so there are some minor differences. For example, line E800 shows "A4" in place of the second "A5", line E810 shows "05" instead of "04", and so on. I'd estimate it's perhaps a 90% match.
Using the E8 I got from Reactive, on the other hand, gives me nothing but a screenfull of "A0", "FF", "C1" and "C6" with a few other random values scattered around. Absolutely none of it matches up with what it shows in the emulator. On a whim, I did E800.EFFF to skim through the whole E8 ROM Reactive sent. Obviously I can't read as quickly as it was scrolling, but the initial appearance of the various values I could briefly make out, along with the last page when it stopped scrolling, suggested the entire ROM is the same way. Then, on another whim, I turned off the system, removed the E8 ROM completely, turned it back on, and did E800.EFFF again...exact same results. So, either the E8 Reactive sent me was never flashed, or it has a problem that simply makes it appear as if it's not even installed. It needs to be said that the ROM they sent didn't come with a 2316 adapter as the site claimed it would. Also, as mentioned earlier, it's quite scratched up, as if it's been inserted/removed several times before.
Hello,
You can not plug an EPROM directly in the Apple without an adaptor.
Take a look here and it should work (thanks to Understanding the Apple II by Jim Sather).
The saga continues with another update. This is more of an FYI for those following the progress of this, since I imagine we've exhausted just about every possible troubleshooting step software-wise.
I contacted Reactive, and they sent me the missing socket adapter they forgot to send the first time around, and it is now installed along with the EEPROM I received from them. Unfortunately, it is still failing the diagnostics, with E8 still indicated as being bad. I tried doing E800.E8B7 again, and most of the values (I'd estimate 95%) match the screenshot provided by Amauget above, but some values are still incorrect. So, even with the adapter, it appears the ROM I got from Reactive is still faulty.
I'm going to contact them again to see what my options are for replacement, but I'm thinking I've passed the deadline for returns/exchanges, since it's been a month since I ordered it (Work and other life events have prevented me from working on this project in a more timely manner unfortunately). Hopefully, eventually, I'll get this up and running again!
Hello torindkflt,
What are the news ?
Have you finally overcome your problem ?
Apologies for the lack of an update. I was finally contacted earlier this week by Reactive, and they are going to send a replacement ROM. I should receive it in a few days. Hopefully this will solve my problems.
That solution is not compatible with language cards. See my page on Apple II prom solutions.
http://www.willegal.net/appleii/appleii-integer.htm
Regards,
Mike Willegal
Absolutely ! Here are a text and schema for a language card compatible adaptor.
Apologies for any confusion. I am not attempting to plug the replacement ROM into the language card. It is being inserted in the E8 socket located on the motherboard. At the moment, I do not even have the language card inserted for troubleshooting purposes.
Hi torindkflt,
There is no confusion at all : Mike simply points out that if you use a bad adaptor to plug the EPROM on the motherboard, there will a conflict WHEN you will add the Language Card.
By the way, the Language Card already got pads in order to use an EPROM directly.
So I am troubleshooting yet another Apple II+ but this one has Integer ROMs on the motherboard.
Boots to monitor prompt, and I can get into Integer Basic.
I have it finally able to boot the Apple Confidence disk, which reports only 32 K of RAM present although all 3 banks are populated.
When it runs, it always reports that the first chip in bank 2 is bad. I have replaced/swapped and re-swapped this chip out to no avail. And I've tried 3 different sets of chips in bank 3 and it won't recognize it.
This is a Rev 4 board with the soldered jumpers - wondering if that might be causing me heartache?
Anybody have any thoughts?
Jen
Hi Jen,
AFAIK, the confidence test doesn't tell you which RAM chip is bad. A single 1 is just printed.
If only 32 Ko are shown, it's perhaps a bad IC in row E.
If you are sure all the RAM chips are good (try them into another machine or swap an entire row in this one), you can try to change the LS139 located at F2.
Hello Jen,
it sounds to me rather more that not the RAM-chips are faulty but
instead the adressing of the RAM banks cause the problem.
The lucky thing is that this is performed by rather cheap LS-Logic chips so a possible
repair would not become that expensive and that chips may be order by a large electronic
supplier like
Jameco
easily within days.
The chips related to adressing of the banks are in the hitlist by chance of being faulty:
2 x 74LS139 at location F2 and at location E2
1 x 74LS153 at location C1
2 x 74LS257 at location J1 and at location C12
1 x 74LS04 at location C11
1 x 74LS20 at location D20
1 x 74LS08 at location H1
or 1 x 74LS32 at location C14
The entire bunch of 9 chips should cost less than 10 U.S. Dollars
and shipping should be the most expensive in the bill.
Checkout that list of chips at the spotted locations if any of that
"suspects" gets more suspicious than it´s companions in the list
- by oxydation at the pins
- bent legs underneath the chip and not inside of the socket
- damaged socket or
- damaged trace to the socket at the solderside.
by that you might even shorten the list ....
otherwise you may swap all in a bunch check out working condition
and then step by step swap back original chips to verify the really faulty chip.
sincerely speedyG
Well I ran that cool memory check routine in Monitor that is in this thread... According to that here are the first addresses that are bad: (there are so many it scrolls off the screen)
445E-FF (DF)
445F-DF (FF)
4559-FF (DF)
455B-DF (FF)
etc
I will try the chip replacement, as I have a few "donor" motherboards that have all of these chips intact still.
Hopefully its one or more of them!
Thanks guys, for giving me hope!
Jen
Ran across some code I wrote years back that loads Integer Basic along with The Inspector/Dr Watson to the language card of the Apple II.
The code loads at $6000, you execute it at $6000 and it takes care of the rest. (loads to the language card)
Once executed, you can type "INT" for Integer Basic or "FP" for Applesoft. Call-151, D000G for Inspector and D800G for Dr Watson.
If you're interested:
https://www.dropbox.com/s/yhhljiy4035hc0y/IntBasicInspectorDrWatsonExecutable%246000.BIN?dl=0
Am working on yet another orphaned Apple II+ and when I run the memory test it flags a single address as questionable:
7FFF-FF
Can anyone here help me identify what this is telling me? (Like which chip or bank it might be?)
Many thanks!
Jennifer
Hi Jennifer,
It should be the second bank, row D.
You can try to swap row D and row E and see if the error moves to the $8000-$BFFF range.
Done!
Turns out 3 of the RAM chips were bad!!
Thank you for the assistance!!
ps: I ran them through a 4116 ram tester that you can order as a kit:
http://neoloch.com/products/Inquisitor.php
You buy the main board/kit and then the additional 4116 tester and build them - fun (and easy) to build and it works great!!
Jennifer
I came across this thread, and having trouble with RAM chips myself, I tried the 48K RAM test:
C050 C053 C054 C057 N 265:FF N 266<265.BFFEM 266<265.BFFEV 265:0 N 266<265.BFFEM 266<265.BFFEV 34:14 (Return)
What I got back is in this video:
https://www.dropbox.com/s/548dj190596paz0/48K_RAM_test.mov?dl=0
Are those numbers on the bottom bad RAM chips?
Edit:
Maybe I'm crazy, but man, I like those things on the screen.
I decided to post this within this thread because it seemed relevant to the discussion.
I just finished a small batch of EPROM converters for the Apple][ and ][+.
I built a set of these back in the early 1980's and sold a few to an enthusiast several years back,
but I decided to take another shot at a more advanced version. I didn't build these to sell. (yet)
What makes this one special is a built-in slide switch that allows you to choose between 2 different PROM sets.
This can be handy for those who want to (say) select between Applesoft Basic or Integer Basic. (for example)
Or, maybe choose between an autostart ROM or a non-autostart F8 ROM.
Integer Basic folks can choose between a D0 Programmer's Aid Rom or (say) a Inspector/Dr Watson ROM
I think you get the idea. The challenge was to fit it between 2 IC sockets sandwiched together to take the least
amount of vertical space. If I remember correctly, I had issue when trying this with a full-sized 7404 IC.
I used gold pin Augat sockets, a 7S04M5 TTL inverter, a 4.7K ohm 1/8W surface mount resistor, surface mount
slide switch, wire-wrap wire and Torr-Seal epoxy as a filler/sealant. A photo of the project can be seen HERE.
I plan on using OTP EPROMS such as the INTEL P2732A or the likes.
Anyway, I'll report on the fit & finish when I get a chance, but in the mean-time I thought I'd share the
progress with you folks. Enjoy!
Hello Abyscat,
Here are the row / address table :
New to the board, here.
Have dug out my Apple II, purchased in 1979. I used it extensively back then, but haven't touched it in at least 30+ years. Took out the Floating Point/Applesoft board from slot zero; took out the Mountain CPS card; took out the speech synthesizer I built; disk controller; parallel printer board; and another board I build with a DB25 on it and I don't remember what it was! It is bare bones, now. D8 socket is empty. We are down to the 16K that came with the box.
Monitor come up, but won't go to Basic with CTRL-B. I've run the memory test (above) and it does what you say. There is something on the screen, but it is covered by the inverse @ characters. Of course, RESET clears it all away.
Any hint how to deal with this? I have forgotten a lot.
Thanks,
Paul
If the machine boots to the monitor and otherwise seems to work but won't go into BASIC then it probably means a bad E0, E8 or F0 ROM. Of course it could also be the keyboard (make sure the B key works and CTRL-G gives a beep) or possibly the decoder IC at position F12.
If you do determine that you have a bad ROM, consider the ROMX as a replacement that also adds many other features.
ROMX.png
Presumably you have a non autostart F8 ROM then?
Have you tried booting any disks? *6<ctrl>p
Have you tried starting it with the Applesoft ROM card in slot zero?
Hi Paul,
Just to clarify, you mention the Apple only has 16 K. It means only raw C is populated with RAM chips, right ?
The above test is designed for 48 K so it's normal ou have error on the 17k -48K range.
You can test the lower 16K with with this command :
C050 C053 C054 C057 N 265:FF N 266<265.3FFEM 266<265.3FFEV 265:0 N 266<265.3FFEM 266<265.3FFEV 34:14(one space)(return)
Thanks Amauget, Baldrick , and Jeffmazur .... I was continuing to research when I came across your responses ... I received no notice, so forgive my delay in responding. I was a heavy user of this machine (Serial A2s1-9214) in its early days, writing 6502 assembly code and basic; used a Teletype model 37 as a printer; did baudot/ascii conversion for Ham RTTY. But, it's been sitting idle for 30+ years. It was quite the investment, $1200 new, plus $550 for the disk drive and controller, and the other cards. I just want it to work before passing it on.
Specifics:
With no cards installed, eight empty slots, I fired it up. It goes into monitor mode (*), but when I press Ctrl-B it does not go into Integer BASIC, but returns:
F002 - A=D9 X=0E Y=72 P=30 S=E2
If I enter E000G, it get the same result, but with different values in the Accumulator, Registers, etc.
F002- A=80 X=00 Y=00 P=B0 S=F9
I reinstalled the additional 16K of memory and set jumpers accordingly. I ran the RAM test, using 7FFE, vice BFFE, because I’ve on 32K of memory installed, and returned no errors.
C050 C053 C054 C057 N 265:FF N 266<265.7FFEM 266<265.7FFEV 265:0 N 266<265.7FFEM 266<265.7FFEV 34:14 (Return)
I pulled all the chips … ALL of them, CPU included … De-Ox’d all the pins; blew out the sockets; and, reseated them all. Same results.
I did the same with the chips on floating point/extended BASIC board and put it in slot zero, with switch up, and powered up. Screen is all white with maybe a dozen colored spots here and there. machine locked. Pulled the card.
I plugged the disk controller in slot six, and tried to boot from the DOS disk using the command:
C600G Enter (also tried 6 CTRL-P Enter) . The drive whirred and the machine returned:
F002- A=80 X=00 Y=00 P=B0 S=F9
*
PROGRAM TOO LARGE
>65535
Had to hit RESET to get back to Monitor (*) prompt. Pulled the controller card.
Hmmm … Now back to the 32K with all empty slots. Used to work!?
The ROM sockets consist of:
F8 F0 E8 E0 D8 D0
C38012 C28079M C28078M C38009 EMPTY EMPTY
I suspect one of the ROMs has gone daft. I see reference to a diagnostic program for the ROMs on another post and will look for that.
I'd attach a photo, if that would help anything, but haven't figured out how, yet!
Will keep with up with this series of posts. Thanks for your assistance.
Paul
Definitely looks like a bad F0 ROM. Try this form the Monitor: F000L If you don't see good code starting with A0 00 LDY #$00, then that is your problem.
Since you've already done the clean/re-seating of chips it probably is a bad chip, socket, or trace (in that order). You could use an ohmmeter to check continuity but probably will turn out to be the ROM or the LS138 at location F11.
Thanks, Jeffmazur. Out of the clouds in my brain, the memory location, F0002, and register dump was telling me where the command failed. The ROM at socket F0, C28079, covers F000-F7FF and contains 1K of BASIC, 1K of utilities.I'm back ... yes, you're right. F000L returns zero after zero after zero with an occasional odd value, all through the range to F7FF.I pulled the 74LS138 Decoder and swapped it with LS138 that decodes for the slots (there's nothing in the slots). No change in behavior.Will pull the motherboard and check for crud between the tracks, but will start looking for a replacement ROM.Thanks. Will continue the endeavor.PaulJeffmazur ...Thanks for the advice. I picked up another F0 ROM, et voila, it works. Goes into integer BASIC and works well. I can access the floppy drive and LOAD/RUN Integer programs from the floppy.I plugged in the ROM board (Floating Point) and tried to boot with the switch up. Still no good. Blank white screen with occasional color confetti. At one point in this resurrection process, I momentarily got a blank screen with Apple ][ at the top of the screen and the floating point prompt, "]". But, the screen quickly turned to garbage. I pulled all the chips off the card; cleaned; and reseated them, but theresult is the same. Takes a power down and reboot to regain control.Will continue on and address getting floating point loaded in another content stream.
Thanks for all your help.
Paul
I am having similar issues with a couple of Apple II+ computers that I picked up. I figured it would be easy to use parts from one to fix the other but that is not the case. Is there anyone that offers a repair type service for issues like this?
I am thinking you should make a new post and describe the symptoms - of one of the machines to avoid confusion.
Then perhaps someone here can help with suggestions.
In the middle of the top row of pins (top photo) the blue wire is not connected or does not appear to be connected to that pin. Why?
Would swapping the banks like this work the same if I have a similar scenario with an error at 7FFF-00 (01)? And what is the meaning exactly of the (01) at the end, compared to say the (04) from earlier in this thread?
sorry if I am asking something obvious, my computer knowledge is not very in-depth and I am learning as I go.
also, should cassette loading work with the same symptoms as the original post and this ram error? If I load from AppleSoft it crashes, but if I load using 800.A00R 800G with hifi, it crashes differently.
it will occasionally say "ERR" but typically spits back and address in the C000-CFFF range, and if I check C040L (I know these are I/O), when it crashes to garbage graphics it says in it "Loading Star Trek", or whatever load failed.
Attached is an image of the garbage and my result from the RAM test:
IMG_4421.png
IMG_4414.jpeg