FIXED! - Apple II Plus Bad Memory/ROM? - The saga continues

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A few years ago, I won an Apple II Plus off of eBay that turned out to have a fault of some sort. After as much troubleshooting as my limited technical knowledge would allow, the problem persisted. I sought assistance on these boards, and after much back-and-forth over things to try and check...no luck. Eventually, an ugly thing known as life forced me to shelve the project.

Here is my original thread on the subject: http://www.applefritter.com/content/apple-ii-bad-memoryrom I strongly recommend you read the original thread, but if you're of the tl;dr mindset, I'll briefly summarize here:

  • There appeared to be something wrong with the Applesoft E8 ROM the system originally came with. Replacing it with two different repro EEPROMs and socket adapter from Reactive Micro didn't remedy the situation.
  • Running a diagnostic program shows ROM chips D0, D8 and E0 as having no errors. The test fails and then aborts on E8, so chips F0 and F8 never get tested.
  • Various RAM chip swapping attempts didn't help, and all RAM tests passed with no errors.
  • The system has a language card, but removing it doesn't remedy the problem.
  • Attempting to boot from the DOS 3.3 disk crashes to the monitor when attempting to automatically load Integer BASIC, even if the language card is not installed. But, Integer can be manually loaded at the Applesoft prompt (With the language card installed), and afterwards Integer programs run normally with no errors.
  • Binary programs run normally with no errors.

After three years, I finally decided to pull it out of the storage and try to tackle the problem again. I managed to snag an original E8 Applesoft ROM off eBay and have installed it...but it STILL isn't working properly. Attempting to boot DOS still crashes to the monitor and Applesoft programs will not run properly. Running the diagnostic disk continues to show the E8 ROM as being faulty. Although it is admittedly possible, I find it highly unlikely that I would have gotten FOUR faulty E8 ROMs in a row (The original the system came with, two from Reactive and the one I just now got from eBay). I know the language card is incompatible with the repro EEPROMs from Reactive, so it now gets removed whenever a Reactive chip is installed, yet the problem still persists.

Now, I will admit that I do have a little bit of concern about having possibly caused some damage to the system myself. When I received my first repro EEPROM from Reactive back in 2011, it did not include the required socket adapter. Not being aware at the time that it was a major no-no, I just plugged the bare EEPROM directly into the motherboard and powered it up. Could this have damaged the system? Beside that, there's also the concern of repeatedly pulling and reseating chips potentially stressing the sockets or the traces beneath them.

Assuming I didn't damage the board myself, I am starting to wonder if perhaps one of the logic support chips or perhaps some traces on the motherboard could be faulty, something that messes with the addressing for the E8 range. Therefore, I thought I'd ask the more knowledgeable people here for some further input on other areas of the board I could check, knowing that the RAM is good and assuming all of the ROM chips are good (Like I said, highly unlikely I'd get four bad E8s in a row). If it helps, here's the various revision and date marks I could find on the motherboard:

  • In the far rear left corner is the date code 41 82
  • Behind the card slots on the edge of the board is 606-X 548 MADE IN SINGAPORE
  • Next to "F" on the left edge of the board is 820-0044-D (C)Apple 1979 Apple II Main Logic Bd RFI

My technical knowledge of the Apple II Plus is just as limited now as it was three years ago, and I am still no closer to solving this problem. Hopefully, with enough brain power from everyone else here, we'll finally get this issue licked, eventually.

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speedyG's picture
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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,
I´d recommend to download from:
http://mirrors.apple2.org.za/ftp.apple.asimov.net/documentation/hardware/machines/
the book:
The Apple II Circuit Description_HiRes.pdf 28-Mar-2012 07:55 59M
after download view page 177 with drawing of the mainboard and mapping of the chip locations used in the circuitdiagrams
and then view page 207 with the diagram C-10 of the ROM-adressing......
i´d finnaly after reading also the previous thread conclude a fault at either the
74LS08 in position H1 or at the chip 74LS138 at position F12.
Alternating there is another chance of malfunction at the Adressbus.
for explenation view drawing C-9 at page 206
(CPU and Bustranscievers )
and focus to the 8T97 at position H4 and H5 ( related to the A10 to A15 Adressinglines ).
Its recommended to first check correct seating of the chips ( no bent pins below chip and every leg correct seated in the socket ) and if seating is correct and no problems with corroding pins present then its recommended to replace that 4 chips ( all chips togethher should sum to amount less than 10 bucks with additional mailing fees...

source in US should be preferably:
http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&freeText=74LS138&search_type=all
and other LS-chips there too....

8T97 probably need search for source at ebay.....
http://www.ebay.de/itm/SIGNETICS-IC8T97N-FNFP-IC8T97N-/311014485416?pt=BI_Control_Systems_PLCs&hash=item4869e86da8
or:
http://www.ebay.de/itm/MC8T97P-MOTOROLA-MC6887P-8T97N-TTL-IC-VINTAGE-1986-16-PIN-DIP-NOS-RARE-/390628225176?pt=LH_DefaultDomain_0&hash=item5af341b098

sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

torindkflt wrote:

Running a diagnostic program shows ROM chips D0, D8 and E0 as having no errors. The test fails and then aborts on E8, so chips F0 and F8 never get tested.

[sound of loud alarm bells is heard]

F0 and F8 have a lot of important firmware that a lot of other things depend on. Had you ever tried other/replacements of those?

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

I tried reseating all of the chips you indicated, this did not help. I will see about ordering some replacements, which should be fairly simple considering I work for RadioShack...that is, assuming they don't go bankrupt before I'm able to order them. Tongue

I have not yet tried replacing the F0 or F8 ROMs, but if the replacement logic chips don't work, I'll give it a try. At the time I ran the diagnostic, I had no reason to assume the F0 or F8 chips were faulty because it seemed to be a normal function of the program to abort the test without finishing once it found a faulty ROM. The diagnostic doesn't freeze or crash at this point, it simply pops up an error indicating which chip it stopped on, then after a few seconds returns to the main menu without testing the remaining ROMs.

I'll try to keep this thread up to date if/when I get replacements.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

I suggest you to dump the memory from D000 to FFFF to a file (under DOS) and post it here for analysis.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

georgel wrote:

I suggest you to dump the memory from D000 to FFFF to a file (under DOS) and post it here for analysis.

It has already been done in the previous thread. And torindkflt also mentionned the Apple couldn't load DOS properly. So everything relies on monitor.

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Apple II forever

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Indeed, booting to DOS is currently not possible, and even on the rare occasion that I CAN get an Applesoft prompt, attempting to run most commands eventually crashes it back into the monitor or freezes the system.

Assuming I somehow am able to get the system working suitably enough to dump the ROMs, what exactly would I need to do to save them to disk? Once they're dumped to disk I presume I can use ADTPro on my IIc (The II Plus doesn't have any serial ports) to transfer the file to my laptop, but the actual dump process is something I've never done before.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

In case that the replacement of the 4 logic chips does not solve the problem
the next task would be to make 6 hires pics:
1 pic front top half of the mainboard ( the section towards the keyboard )
1 pic rear top half of the mainboard ( the section towards the slots ) top indicates the component side
1 pic of entire bottom ( solderside ) of the mainboard
additionally i recommend to make
1 pic of the componentside of the languagecard and
1 pic of the solderside of the languagecard
and finlly 1 pic of the languagecard inserted in the slot 0 and cable plugged to socket at mainboard
pic taken with view to compside of LC and MB.
All pics schould be with size of approx. 3000 pixel x 2400 pixel and at least 300 dpi
( pic size 2,5 to 3 MB ) good lighting ( if possible without flashlight )
very good focus ( permitting to zoom in pic and inspect pins and reading of printings at top of ICs )
for example of pictures i have commented view :
http://www.applefritter.com/content/problems-apple-ii-clone-named-pluto-no-color
view the pics that the links have been published
or at:
http://www.applefritter.com/content/rev-0-apple-ii-troubleshooting
or very good example for the taken pictures:
http://www.applefritter.com/content/troubleshooting-language-card

the better the pictures taken, the better the performance of the analysis....
speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Ok, I'll keep the pictures in mind in case the logic chips don't work.

In the meantime, I managed to coax the system into a DOS prompt, and I -THINK- I was able to dump the ROM using the BSAVE command, provided I got the syntax correct, that is (BSAVE ROMDUMP,A$D000,L$2FFF). In the previous thread I merely examined the E8 ROM, so this time I dumped them all just to be absolutely sure. Now I need to figure out how to get that file from the disk onto my main system for analysis, which I presume will require ADTPro and a USB serial adapter, the latter of which I currently cannot locate.

Or, here's a question...could I use my IIc to somehow compare the dump to the original ROM images? If I recall correctly, there's a copy of the Applesoft ROM on the DOS 3.3 master disk, and unless they're not saved in the same format, shouldn't it be possible to BLOAD them both into different areas of RAM and then compare them that way? If so, this is something I should be able to do right away.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

As far as i remember you mentioned at posting quite back ago that the IIc does not have serial ?
The reason for this question is, that under normal conditions the IIc has a internal serial port.
If that port is not damaged you can transfer with any communication program the files with
binary transmission protocol to any serial port at the IBM and view that file at the IBM and
even compare with Epromfiles that you may also view within AppleWin Emulation program or
even better with a eprom programming program.
I usually use in that case the program which is used with the Willem Eprom programmer because
that software is availiable as open source from Internet. The other possibility would be to find
a Apple program related to a Apple II Eprom programmer ( by searching the interfacecard related
directories and searching there for disk image of related disk )
entry point for search would be:
http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Chip%20Programmers/

sincerely
speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

The IIc does have a serial port, but I have no other computers with serial ports on them, and I have misplaced my USB to Serial adapter cable. So at the moment, I have no way to connect either the IIc or the II Plus to any other system. During the time this project was shelved I had moved, and fear it may have been left at the old house.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

this makes a compare of eprom files and eprom dump to become a "hard-core task".....
maybe david_schmidt or amauget has idea of simple solution....
sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hard core indeed. It might be possible to compare the disk-based Applesoft to your ROM, but I'm not sure I'd trust enough of the machine's subsystems to believe any results.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

True. For all I know the dumped ROM image could be corrupt despite the II Plus reporting it as having saved successfully. Also, it did take three tries to finally dump the ROM without any errors, the first two times it died with an I/O error. Whether that's from the mystery fault or a bad disk, I couldn't say (I currently only have three writable disks available to me, and they're all quite old). So, even if I did use the IIc to do the analysis, it might be futile.

I think for now I'll hold off until I can get the replacement logic chips, then go from there. It'll be at least a week before they come in though if I do order them through RadioShack (I want to try them first because I'd get an at-cost employee discount and free shipping to the store I work at). Otherwise I found a couple places online that has all of the replacement chips I need.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

double strike posting....
sorry

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

In the meantime while waiting for the chips to arrive, it might be a good idea to
revisit this thread from 2 years ago:
http://www.applefritter.com/content/apple-ii-graphic-fault
and
http://www.applefritter.com/content/help-apple-ii

speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Got the replacement chips ordered from Jameco, even the 8T97 (A compatible part number for it is 74LS367). Now to wait for them to arrive.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

There is a difference !
74LS367 are a bit more slow than 8T97 !
They are pincompatible... but:
8T97 are about 20% faster than the 74LS367.....
maybe they will work....
- but in case they do dot work it is highly recommended to use the 8T97 !

In case you still want to use 74XX367 it is recommended to use the 74 F 367 !
sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

I did not know there was a difference. When I put 8T97 into Google, I found several websites that showed 74LS367 as being a compatible replacement and assumed it was the same thing. Unfortunately it is too late now to modify or cancel the order. Hopefully I won't have to replace them and it's one of the other chips causing the trouble.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

speedyG wrote:

There is a difference !
74LS367 are a bit more slow than 8T97 !
They are pincompatible... but:
8T97 are about 20% faster than the 74LS367.....
maybe they will work....
- but in case they do dot work it is highly recommended to use the 8T97 !

In case you still want to use 74XX367 it is recommended to use the 74 F 367 !
sincerely speedyG

It is not the speed that matters in A2. It is the output driving capability of 367 that might be insufficient sometimes.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

speedyG wrote:

They are pincompatible... but:

If a chip is pin compatible then why would there be a problem of any kind?

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

If indeed the part I ordered is 20% slower than the original 8T97, I presume it could cause issues/random glitches if its internal switching isn't able to keep up with the data bus. The processor could tell it to do something, then crash because it wasn't able to finish fast enough. Granted we're only talking about ~1MHz here, but the possibility is still there.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

insanitor wrote:
speedyG wrote:

They are pincompatible... but:

If a chip is pin compatible then why would there be a problem of any kind?

Hello insanitor,
as explained the chip is pincompatible. This only means that each pin at the chip does the same as the replacement.
But if the chip is slower there might rise a conflict in some cases while the CPU is setting up the adressing of the computerbus ....
you must always bear in mind, that only small part of the cycle time is used to set an adress while the following part expects the cell at the adress ( memory or ROM ) to display correct / valid data at the databus when strobe signal follows adress-setting.... in general as mentioned by georgel for the computer itself this is not that much important....
but for example if in use with some interface cards ( specially coprocessor cards like the Z80 CPM card ) are critical in timing and in later use suddentliy this issue appears to the user without warning.... resulting to a "frozen" system

same is valid to the driving capability as mentioned by georgel...
the more interface cards are inserted to the system the higher the "load" is given to the output of the chip
and this also affects to the reliability.... it might lead to an kind of "breakdown effect" where the chip is not able to output the required power to the adressing bus and causing the voltage to drop below of the specified limits
causing the following chips at the bus not to recognize reliable a "high" signal....

sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

That makes sense. When I bought my original Apple II collection, one of my Apple iie computers had one bad RAM chip on the motherboard. I replaced it with another chip which was supposed to be "pin compatible" but it was from a different company.

BAD IDEA. The system scared the living daylights out of me. So much so that I don't even remember exactly what happened. I think it damaged one of the disk controller cards. Anyway, that's how scary it was for me.

So I then bought an 80 column card which had a complete set of RAM chips for the iie and I inserted them in.

Haven't had a problem since.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello insanitor,
in fact that problem with the IIe can only be compared in small part...
the RAM chips are classified in speed by the attached numbering:

4116-15 for example specifies timing to be certified at 150 nano seconds
4116-2 for example specifies timing to be certified at 200 nano seconds
4116-3 for example specifies timing to be certified at 300 nano seconds
so in that group above the -15 is fastest
4164-70 for example specifies timing to be certified at 70 nano seconds
4164-15 for example specifies timing to be certified at 150 nano seconds
4164-2 for example specifies timing to be certified at 200 nano seconds
and in this group -70 is fastest
most RAM-chips of that days have been equipped by that kind of timing-coding

so for RAM-chips the following statement is valid:
the upmost first quality criterium is the certified speed
the company is the second quality criterium...

the company as criteriun is result from the fact that different companies have different quality standards and
quality assurance standards.... some have better testing and selection process ...
at some companies in that former days the selection process was rather more a "guessing process"

that´s the reason it´s not good idea to mix different companies :
slight minor differences is selection quality.... small but sometimes bothering differences...

RAM-chips are organized in ROWs to form a byte
therefor its recommended to make sure at least within the same ROW ( i.e. group forming a byte )
the chips should be made by same company...
difference of company in different rows do not cause that much problems...
speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,

If you manage to boot DOS, maybe you can try to boot the Dealer Diagnostic program. It has the ROM verification embedded.

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Apple II forever

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

amauget wrote:

Hello torindkflt,

If you manage to boot DOS, maybe you can try to boot the Dealer Diagnostic program. It has the ROM verification embedded.

Hello amauget,

remember reading message #3 ?

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Alright, I received the replacement chips today and installed them, although I made a mistake while ordering and only received one replacement (of questionable compatibility) for the 8T97 chips, so I had to try swapping them out one at a time. No dice, diagnostic program is still showing E8 ROM as being bad and DOS is failing to boot.

The next step, as requested, will be uploading high-res photos of the motherboard, but this shall have to wait as I am currently on lunch break from work and do not currently have the time to fully disassemble the system. Would you like me to take pictures of the bottom of the board as well, or just the top?

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Picture from bottom of the mainboard is only needed, if there is any kind of modification or wires added....
if it´s just the bare board there will not be any need for taking picture....
sincerely
speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Ok, here are high-res pictures of the motherboard. Apologies for the flash glare, I did not have any other suitable lighting.

Whole Board

Top Third

Middle Third

Bottom Third

The E8 ROM that's currently installed in these images is the one it originally came with. The chips at H1 and F13 are the new ones (I tried the new 74LS138 in both F12 and F13 just to test, it didn't make any difference). I'll need to re-order proper 8T97 replacements, but the pin-compatible one I ordered didn't help when testing one socket at a time.

Assuming I can find some, I might also try replacing the F0 and F8 ROMs. I want originals though because I want the language card installed, so I'll have to keep an eye out on eBay. There's currently none up there short of buying a whole motherboard for $50+ (Currently not possible for me).

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,
while waiting for the 8T97

before testing:
in row E the one RAM chip at position E3 ( the one in the white socket ) has been taken from the languagecard...
i assume that the chip from NS ( National Semicuductor ), being same as the other chips in that row,
is still located at the languagecard..... please swap this chip with the one at the languagecard from NS with
the aim to have afterwards all chips in row E of the same kind and manufacturer !

you can perform at least 2 tests by swapping according to the picture below:
1st test:
Pull chip marked as A and set besides
Pull chip B and insert that chip in position formerly occupied by chip A
Pull chip C and insert that chip in position formerly occupied by chip B
Insert chip A formerly pulled and seated aside in position formerly occupied by chip C
result should be:
in postion of former chip C now is the chip from ST( from Thompson )
and in position of former chips A and B are now both chips from f ( Ferranti )
then try to boot and check if behaviour of computer changes and report here
2nd test:
swap the 2 74LS08 marked as 4a and 4 b !
then try to boot and check if behaviour of computer changes and report here

I guess you have recognized that only in ROW C there are 4116 RAM chips from Mostek that have been certified by Apple
( marked with the famous small apple logo stamp )
while in ROW D and E there are compatible to 4116 chips from National Semiconductor....
this indicates that the computer was originaly equipped with 16KB and later upgraded to 48 KB.
also to be recognized: the E0 and the E8 ROM do not seem to be from the same set...
they rather more look like if they have been replaced in some time ago....

This might be wrong immpression by lighting.... but it seems that several chips are not relly inserted firm in their sockets...
i´ve marked them with light violett shade:

please check out that chips and check the rest of the chips for being tight inserted in their sockets....

sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Unfortunately, the language card does not have any RAM chips that are identical to the others on the motherboard. The ITT chip is the one that was in the socket next to the flying lead on the card. Here's a closeup picture of the RAM chips on the language card compared to the upper row of RAM on the motherboard.

Could this be a memory issue, despite the dealer diagnostic passing all RAM tests both with and without the language card installed? I might try swapping the RAM from the language card onto the motherboard so the top row all has the same chips, but this will have to wait until I have more time, as will swapping around the other chips. Of course, this means then the language card itself would have the mismatched RAM, and I probably wouldn't be able to use it until that were remedied.

I did already reseat all of the chips though. I didn't remove them entirely from the sockets, instead I used my IC extractor to gently rock them back and forth to hopefully clear up any oxidation, then pushed them back in firmly. Otherwise, the chip swapping I'll have to do later tonight. Thanks for the tips though.

As for the apparently mismatched ROM chips, this is how it was when I received it. The dealer diagnostic says there's nothing wrong with the E0 ROM, so I presume there's typically no problem with them not being from the same series. Am I mistaken in assuming this? If so, then my only option would be to replace ALL of them, which is prohibitively expensive currently as it will likely require purchasing a whole motherboard or Applesoft-equipped firmware card. None of the other E8 ROM chips I have are an identical match to the rest.

I do agree though that this board had been worked on before I received the computer, as I also noticed the character generator ROM has been replaced.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,
just for explenation:
while booting the apple tries to detect how much memory is present and the depending to the result of that test
it starts loading portions of the disk to highest verified part of memory - preferably to the languiagecard.....
so depending to the result of testing the RAM from 32kB to 48 kB and the testing of the 48 kB to 64 kB
the computer decides to load stuff in the card or not....

and the result of the primitiv RAM test also determines if the computer believes to be able of using only 48kB of 64 kB.
In case the E row is not reliable the computer even refuses to use the E row of chips but instead believes only to have 32kB.

Unfortunatly i have a problem with the chips at the languagecard.... some chips of the 9116 series
are similar but not totaly compatible with the 4116 chips in that way, that some only use 1 supply voltage
of +5 volt but not using +12 volt nor - 5 Volt.... as far as i remember that pins are marked to be NC in
such case in the datasheets meaning to have no connection...
under normal conditions this schould not bother us - but without the specific datasheet i´d prefer to keep at
the "safe side"
and leave the RAMchips at the languagecard untouched.....

Like i explained in the posting it might just be an immpression caused by the lighting to assume some chips
not completely inserted in their sockets.... this impression might be wrong... if you claim to have checked
correct
and firm seating in the sockets then no further check is needed....

I do agree that if the dealers disk does not mention a mistake with the E0 ROM, then it´s not a problem
with the series but rather more only with one chip or with the related decoding by the adressing chips
of that single chip or with the adressing lines to the adresses above
of one adress affecting all adresses
above that point
....

that´s also the taskline i have been running along from the beginning of this thread when i joined this thread
till now....

this means that the problem is located in the decoding / selection of the single ROM chips them selves....

short explenation:
if the adressing line of the highest 16kB is selected then there is a decoding performed to decide if
the 16 kB of RAM at the languagecard is selected or if the adress is to be used at the ROM chips or
if the adress is to be used with the so called "softswitches" ( meaning cassetteport, slotadressing, or selection
of data from gameport etc. )
I believe the problem to be located in that specific part of the adressing process.

if the swaping like explained in my last posting does not change behaviour and therefor lead to other conclusions
i´d resume to stay with testing the problem with one of the 8T97 chips.... otherwise in the
"decoding process" of the ROM chips only very few mistakeoptions are left....

besides ... did you check the bottom of the mainboard for added wiring ? In former days it was quite
common behaviour that users performed mods for adding lower case letters to the computer and the changed
Char Eprom might be indicator of such modification...

some guys performed modification at top of the board - but some instead prefered to carry out the mods at the
soldering side.... - if such modification has been performed i must inspect that.... sometimes by time wire
gets loose or broken off....

sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

I tried swapping around the chips you indicated, and it didn't make any difference. I'll see about ordering proper 8T97s, it's looking like the least expensive way though will be to buy a lot of 25, and I definitely don't need that many!

I also double-checked the chips you said appeared to not be seated fully and verified that they are indeed firmly seated all the way, but it still didn't make any difference. I checked the bottom of the board and did not see any extra wires or jumpers.

In regards to the mismatched RAM, I can look into finding fully-matching replacements for all three banks. You said to leave the RAM currently on the language card there? Or, should I match it as well? For the record, this is the results for the RAM test from the dealer diagnostic program with the language card installed.

There's currently a II Plus motherboard on eBay that the seller claims is a working pull. It has no bids and there's only one day left in the auction. Against my better financial judgement, I might just go ahead and buy that for the chips, if not to just swap it in with the current board. I notice, though, that it also doesn't have matched RAM, so I presume I'd have the same potential issues as the current board if indeed that's the cause of my problems.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,
i in fact explained the RAM itself not to be the problem at the moment. It might turn to become a problem if
you intend to use later a Z80 card with CPM. But for normal use it´s O.K., if the Dealers Disk tells it
to be O.K.
In which country are you located ?
I have a bunch of 8T97 so i can mail you by letter in airbuble envelope 3 or 4 of them.
On long term i guess it´s a good idea to have a spare mainboard for parts....
if the seller has reliable reputation by feedbacks the announcement that the board is
from a "working pull" might be reliable too.... so then it´s a question of price....
it might even solve the entire problem just by swapping the mainboards....

After the tests above did not change behaviour i´m checking the remaining options....
i´ll note them here in a message till this afternoon ( within next 7 hours ) ...
At the moment it´s getting getting closer to the confirmation of being a bad E8 Eprom.

sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,
lets just repeat:
first task should be to examine the 8T97 chips as explained in previous posting.

Just to explain one point:
if we examine the previous part of the adress decoding there is a part that is also

Related to that process in previous stage before switching the high 16 kB between RAM, ROM and softswitches.
( mentioned as "Block switching" )
Within the previously mentiond Book "the Apple II Circuit description" there is a signal in the circuit diagrams that is
related to that "block switching" and mentioned in the plans as "SOFT5". In general it´s related also to switching between Text, Graphic and Hires pages......
There is a slight minor chance only that this signal has in early stage a fault that effects the Block switching.

I sorted this part too and there are some tests that might be performed with no cost and some with minor cost...:

A You may check the function of the 74LS138 located at H12 by swapping it with the other 74LS138 at location F13.

At each step please also try to boot the Apple and examine if behaviour changes !

If you perform more steps at one time and then test you won´t know which task caused the change and what´s to blame....

B will be a swap of the 74LS257 at location J1 with the 74LS257 at the location C12.
check by booting again

C will be a circle swap like explained in the picture and swapping the 74LS74 chips marked in the picture and moving them in the direction of the arrows.

again check with booting attempt....

then finally there are some changes of chips .... i give priority to price and availiability ( meaning the chance to get that chip from another board and chance to swap:
G the 74LS00 at location A2
F the 74LS04 at location C11
D the 74LS139 at location F2
E the 74LS20 at location D2
and
H finally 74LS283 at location E14 (this will become difficult to find and change )

again : please give feedback.... if none of this tasks causes a change, then the mistake will finally be proof the be a bad E8 Rom.

If then the ROM is changed there still might be trouble because the F0 and F8 ROM have not been tested yet .... so first thing will be to check that ROMs to by use of the Testdisk too!
Then next step will be testing the pages of the display / memory ( switching of Text / Graphics and Hires )

and of course at each test the keyboard shall be pluggud in its connector at location A7 !
sincerely
speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

I believe I was able to rule out the 74LS00 and 74LS20. The language card had both of those chips, so I tried swapping them onto the motherboard one at a time, checking to see if it would boot each time. No change even with both chips swapped. Just in case though, I still have them on my shopping list, along with a 74LS74 for the language card (The one on there apparently still works, but I just noticed it's cracked).

I'm looking into getting replacements for the other chips you mentioned. Since I was confused about compatibility with the 8T97 earlier, I thought I'd post a list of what I've found before buying, so you can verify that they are 100% compatible replacements.

74LS00 - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_46252_-1
74LS04 - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_46316_-1
74LS139 - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_46623_-1
74LS20 - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_47095_-1
74LS283 - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_47423_-1
8T97 - http://www.ebay.com/itm/4-PCS-N8T97N-High-Speed-Hex-3-State-Buffers-Inverters-DIP-16-IC-/221611311781?pt=LH_DefaultDomain_0&hash=item33991042a5

As I said before, I've tried four different E8 ROM chips on this system so far. I admit it is possible, but doesn't it seem very unlikely that all four of them would be defective, especially if two of them were flashed EEPROMs from Reactive? The most plausible way I could see this being the case is if there's something else wrong with the board that was actually damaging each ROM chip that I tried. Could that be a possibility? Perhaps bad voltage at the E8 socket or a short there?

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindklft,
yes all parts you passed over the links are O.K. !
If you like, you might extract the E8 Rom and take a picture of the area surounding that chipsocket within diameter of 10
centimeter from top and from solderside as closeup with good focus...
then i will inspect that area very tough....

but my best average tip are still the 8T97 chips....

If you want to checkout the socket with multimeter :
http://pdf1.alldatasheet.com/datasheet-pdf/view/22809/STMICROELECTRONICS/M2716.html

Pin 12 = VSS = GND = 0 Volt
Pin 24 = VCC = Supply Voltage = + 5 Volt
and Pin 21 = Vpp in normal operation mode ( not programming ) = Vcc = + 5 Volt !

just a stupid question: of course you have examined that at CPU pin 18 to pin 20 ( A9 to A11 )
and pin 22 to pin 25 ( A12 to A15 ) are correct in the socket and not "folded back" below the cpu ???
sincerely
speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

I did check the processor, none of the pins appear to be bent and it is firmly seated in the socket. I hesitate to remove and reseat it because I do not have an IC extractor tool large enough to fit it, and fear using a screwdriver as a lever might damage it.

As requested, here is a closeup picture of the E8 socket and surrounding area. I apologize for the poor image quality, this was the absolute best I could get with a camera that is horrible at closeup images and the lighting available to me (I don't have a flatbed scanner, otherwise I would have just scanned the board in).

I'll have to see if I can locate my multimeter. I misplaced it during my most recent move. In the meantime, I'll order the 8T97 replacements...and whether it's a good decision or not I don't know, but I went ahead and bid on the claimed-working motherboard on eBay. I'll know in six hours whether I won it or not.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Ok, I found my multimeter and was able to test the voltages at the E8 ROM. I had to test it it with the ROM chip inserted (The original, not the Reactive EEPROM), as my probes are too large to fit directly into the socket itself. The ground I used was at the unpopulated three-hole connector located between E1 and E2. Here's the results I got:

-Pin 12 measured 0 volts. I also verified continuity to ground for pin 12, it checked out ok.
-Pin 24 measured 5 volts.
-Pin 21 measured 4 volts.

Pin 21 definitely seems to have a low voltage, but I imagine there's a margin of error within which the chip will still function normally. Does it fall within that margin? If not, I presume I'll have to begin looking at capacitors, resistors and other non-IC components. Note that this may be difficult for me, as my multimeter is a basic analog model that cannot measure capacitance or other more advanced features (It only does voltage, current and resistance).

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindklft,
the measured values are O.K. ....
pin 21 is still within limits....
in fact it toggles some small periods to 0 Volt ( while being toggled off ) but stays in general at +5 Volt...
so in fact a analog measurement device will make some kind of "interpolation"
displaying a kind of "avarage voltage summary" because it´s too slow to react to fast switching....
so that value is O.K. ....

remark to closeup picture:

It seems to me that the 8T97 closest to the CPU has very slight change in the surface of it´s case
- this might indicate that that chip has been "running hot" some time months ago bleaching the printing on top
of the case and slight color exchange - compared with the other 2 x 8T97 chips...

This sometimes happens if in former days a interfacecard was inserted in a slot and having a shortcut at the
interfacecard.... even if - after detecting that damage - the switch off power might have been a little bit late
causing the chip to be altered inside a bit.... in such cases a chip even might fail months later....

-----

Some slight change ( in this case rather more scratching ) in the case is at the CPU at the end where the
high adressing pins are located ( close to the side of the 8T97 ) - but that change seems to
be result of CPU extraction and re-inserting to it´s socket.....

sincerely SpeedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Well, I managed to snag the supposed-working motherboard from eBay. I'm planning on using it as a source of further chip replacement, although if it comes down to it I might just swap it out with the current board and call it done, provided it is indeed in working order as the seller claims. I'm going to at least try replacing the 8T97s on the current board since I've already ordered them.

Regarding what was said earlier about mismatched RAM potentially causing problems with Z80 cards and similar...I currently have no plans to install any such cards. My goal for the time being is to simply get this system in a similar configuration to the Apple II Plus my family owned back in the early 90s, all it had that I can recall was a disk controller with one drive, language card and what I believe was a firmware card (All I remember is it had a switch on it that stuck out the back).

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt.
first of all congratulation for the successful purchase.....
lets wait and check the arrival of the chips and the board....
that should solve the task and finally both boards should become the status "working condition"
i´ll wait for the feedback...
sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Out of curiosity, how can I tell if the current motherboard is the one that originally shipped with the case? If it is, that gives me even more incentive to repair the current board if possible, rather than swap it out.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

hello torindkflt,
at the one side you have the label with serial no. at the bottom of the case,
at the other side you have the year and week of manufacturing noted close to the powerplug of the mainboard.....
and third there is the revision type....

by these three factors a expert can tell you if the mainboard has been swapped according to the known
timelines of production....

At the other hand: even in Appleshops the technicians often performed such a swap
to solve a repair fast and satisfy the customer by fast service....

so it was common to first swap the board and later rrepair it and
when next demand for repair came again first swap and then repair....
keep the repaired board on the schelve for the next task of repair...
and so on...

sincerely speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Well, today I received the replacement 8T97s. Popped in all three...nothing. Problem still exists.

At this point, I'm just gonna call my attempt to repair this motherboard a loss, and I'm just gonna swap out the board when I get the one from eBay. I MIGHT try again to fix it sometime in the future, as I know there's still a few other chips to try replacing. But for the time being, I've already spent more money that I was prepared on this restoration, and need a bit of a break from buying any additional parts.

I'll let you know how the new board works out when I get it in. I apologize for wasting your time with this seemingly-futile endeavor, yet still thank you for your assistance.

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,

that´s O.K. - even experienced user sometimes make a break while repairs
and let former days pass by and review past path of a task....

just continue at the point you want to continue....

due to symptoms i would have expected the mistake in the later part of decoding we have now completely examined...
if the problem is located in the earlier part ( related to the "soft5" part explained above ) i would have expected
also some strrange effects at switching of the graphic pages too - which have not been mentioned yet....
if you continue, it would be good to examine that in first "next step" ....

lets hope the mainboard ordered, jumps in the breach at first start as replacement....

sincerely
speedyG

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Re: Apple II Plus Bad Memory/ROM? - The saga continues

Today I received the replacement motherboard I ordered from eBay. I decided to just save time and try swapping it out with the current board, since the seller claimed it was a working pull. Unfortunately, it turns out the replacement board is even LESS functional than the original! Nothing but garbage on the screen at power-on, no beep or disk access. It was at this time that I discovered the replacement board is actually missing a chip, the 9334 at F14. So, I tried putting the 9334 from the old board onto the new one, yet it didn't have any effect, still screen garbage.

Next, I swapped the LS283, LS04 and LS139 chips between the two boards, and reinstalled the original board. It still failed the ROM test. Then, I took the E8 ROM from the replacement board and tried it in the original board. That brings the number of different E8 ROM chips I've tried on the original board up to five. I ran the motherboard ROM diagnostic again...

...IT PASSED! So did F0 and Autostart!

Cue the choir, it's time to sing "Hallelujah!" I am now the proud owner of a fully-functional Apple II Plus! Thank you Speedy and everyone else for all the assistance!

Now, I need to figure out what to do with the board I got from eBay. Obviously I could try to repair it, but that would have to wait for another day, as I want to tackle the faulty disk drive on my IIc next. I don't know if I could return it since I salvaged parts from it, I might contact the seller and inquire.

Again, thank you all for the help!

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Re: FIXED! - Apple II Plus Bad Memory/ROM? - The saga continues

Hello torindkflt,
i´m happy to hear that you finally solved the task and that some of the experience solved in the task
was usefull to perform the final task....
later if you like to make a set of pictures ( screenshot from Monitor and mainboard ) we might take attempt
to the second board....up till then enjoy the running system....
and like posted in the other thread just read the pages related to the drives with eyemark to the parts related
to the IIc drives..... if you walk along that pages carefully i´m quite sure you´ll also solve the issues with
the drive....
sincerely speedyG

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Re: FIXED! - Apple II Plus Bad Memory/ROM? - The saga continues
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Re: FIXED! - Apple II Plus Bad Memory/ROM? - The saga continues

It'll be time before the external IIc drive I ordered comes (Even if I can't/don't swap the mechanisms I wanted a second drive anyway). In the meantime, I might see what I can do with that second II Plus board. I'll start a new thread for it though since the subject of this thread is now resolved. Thanks again!