-
Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.
Unhappy Macintosh 128k, Thick vertical lines
- Thread starter gubbish
- Start date
JDW
Well-known member
Whoomp! There It Is.
By all means, clean that board! I'm speaking to everyone here at the 68kMLA with this statement. Before you try anything else, you should always open the case and clean off dirty parts. Dirt and grime, not to mention leaked or dead capacitors, are the source of many electronic product problems.
By all means, clean that board! I'm speaking to everyone here at the 68kMLA with this statement. Before you try anything else, you should always open the case and clean off dirty parts. Dirt and grime, not to mention leaked or dead capacitors, are the source of many electronic product problems.
beachycove
Well-known member
JDW: Good to hear from you. How are things in your part of Japan?
Mac128
Well-known member
Those DRAM chips are the large silkscreened Apple logo. My experience has been without exception that usually one or more of those chips will have failed by now. This is not the case for non-Apple branded DRAMs. Nothing conclusive, but I blame bit rot. If the poor storage conditions are at fault, then you may well find several chips have gone bad. But by all means clean it up first, reseat the ROMs and see what happens. Also looks for obvious signs of corrosion around the solder joints and pins.
That Resistor array was a standard modification to the 128K whenever they came in for repair (which tended to be a lot) in order to prevent a certain kind of lock-up that tended to happen. That's why there are so few original unmodified 128K boards, since almost always, at least this was done. Nothing to worry about. Focus your efforts on cleaning it.
As JDW points out, considering the storage conditions, there could be some caps on the logic board that have leaked. Though the state of the analogue board is definitely a good sign. Be sure to adjust the voltage on the analogue board before powering it up for use, as the caps are most certainly at the end of their life.
Speaking of JDW, good to see you casually posting. Had almost forgotten you were in Japan. I trust you and yours are well. Sending good thoughts across the Pacific.
That Resistor array was a standard modification to the 128K whenever they came in for repair (which tended to be a lot) in order to prevent a certain kind of lock-up that tended to happen. That's why there are so few original unmodified 128K boards, since almost always, at least this was done. Nothing to worry about. Focus your efforts on cleaning it.
As JDW points out, considering the storage conditions, there could be some caps on the logic board that have leaked. Though the state of the analogue board is definitely a good sign. Be sure to adjust the voltage on the analogue board before powering it up for use, as the caps are most certainly at the end of their life.
Speaking of JDW, good to see you casually posting. Had almost forgotten you were in Japan. I trust you and yours are well. Sending good thoughts across the Pacific.
JDW
Well-known member
I will keep this brief so as not to upset the topic of this thread. Thank you for your concern. Some of you have sent me a PM, which I sincerely appreciate. Thankfully, we are located 8-hours by car from the quake epicenter and as such we sustained no damage from the quake, although we did feel it very noticeable for more than two full minutes. The concern at this point, as I am sure you know, is radiation. Winds are strong here in Japan. Given sufficient leakage from the plant it is possible that some parts of Japan could experience Black Rain, not too unlike what occurred after WWII. Your prayers and support for Japan is needed and appreciated.
But getting back on-topic, I'd just like everyone to know that I've swapped out the caps on more than just my SE/30. I've swapped out the caps on my IIgs keyboard (attached to my SE/30), which got it working well again. I've also swapped out the fluid-filled caps on my 512k logic board too. After all these years, it's illogical and silly NOT to replace them as they can be the root cause of more trouble than you think.
Best wishes.
But getting back on-topic, I'd just like everyone to know that I've swapped out the caps on more than just my SE/30. I've swapped out the caps on my IIgs keyboard (attached to my SE/30), which got it working well again. I've also swapped out the fluid-filled caps on my 512k logic board too. After all these years, it's illogical and silly NOT to replace them as they can be the root cause of more trouble than you think.
Best wishes.
Hi again,
Before continuing, wanted to send my support to the people in Japan.
I visited friends in Sendai last summer - thankfully they are safe but may have lost their home, I haven't heard more than that they are well. Let's all hope the radiation worries subside soon.
So, back to the Mac 128 saga -
much more progress since the last update. So, I cleaned the board up with denatured alcohol, removed the ROMs and cleaned those too. After it was looking pretty and clean I put the board back into the Mac, turned it on - and no change. Still the vertical bars with the garbage pixels. Time for the next tactic.
At that point, I had a feeling that the RAM still had something to do with it but wasn't quite ready to charge into the desoldering stage quite yet. I decided to try taking the ROMs out of the known working 128 that I bought in the same group of Macs and swapping them into this board to see what would happen.
Opening up the working 128 revealed, if it's possible, an even dirtier mac than the first one! This second 128 board was absolutely covered with dust, and even had what looked like seeds and other natural bits of debris. Who knows what conditions these Macs were stored in. But that board did work despite the dust, so I grabbed the ROMs, cleaned them up a bit, and swapped them into the logic board of the non-working 128. Put that board back, fired it up and...
*bong*
with a sad mac code of 020400.. and a lot of stray pixels all over the screen. The sad mac code was fortunately readable but the numbers were missing several pixels. So it looks like at least one ROM from the 128 board was bad.. and in addition to that the sad mac code indicates that the RAM at G7 was bad.
Now it was time for desoldering.. I removed the G7 ram (an MT4264) and replaced it with a TI 4164 chip. I opted for the method recommended in the Pina book of clipping the leads off at the chip and removing them afterwards. Not sure what experience others had with this, but I don't think I had the right type of cutters for this job. Mine were a little too large and too blunt to effectively clip the leads off close to the chip. If anyone has any recommendations for good cutters for this, please let me know.
After adding this chip, the board went back in the Mac, turned on -
*bong* - Sad Mac 044120
-- 3 more chips to replace now, G11, G5, and F10. I replaced each of these, testing after each replacement, and things progressed as I expected - after replacing G11, the code was 040120. After replacing G5 - I had a momentary scare when I turned the mac on and instead of a regular bong and sad mac there was a distorted bong and a screen full of garbage, with the hint of a sad mac message in the middle. I refreshed the solder connections on the new G5 chip, tried again, and phew, all was well, with a sad mac of 040020.
Last chip to be replaced was F10. Replaced that, started again and -
** SUCCESS **! Regular screen, asked for a boot disk. From the external floppy, booted up system 1.1 and it worked!
So in total 4 of the DRAMS were bad, and one or both of the ROMs. I haven't gone back to figure out which one was the culprit. Looks like now to have both 128s running properly I'll need to find one or both ROMs.. or perhaps burn a replacement PROM. Does anyone have any experience with using currently available PROMS or EEPROMS for ROM replacement? I was looking into this for an Apple II+ repair at one point and it looked like the pinouts were different, but could be adapted with a special socket.
Anyway, thanks for all of the advice, and I'm glad the machine eventually worked. One more Mac liberated. Now I just need to find an easier way to get those bad RAMs off of the board, that part of the process took me way too long.
Before continuing, wanted to send my support to the people in Japan.
I visited friends in Sendai last summer - thankfully they are safe but may have lost their home, I haven't heard more than that they are well. Let's all hope the radiation worries subside soon.
So, back to the Mac 128 saga -
much more progress since the last update. So, I cleaned the board up with denatured alcohol, removed the ROMs and cleaned those too. After it was looking pretty and clean I put the board back into the Mac, turned it on - and no change. Still the vertical bars with the garbage pixels. Time for the next tactic.
At that point, I had a feeling that the RAM still had something to do with it but wasn't quite ready to charge into the desoldering stage quite yet. I decided to try taking the ROMs out of the known working 128 that I bought in the same group of Macs and swapping them into this board to see what would happen.
Opening up the working 128 revealed, if it's possible, an even dirtier mac than the first one! This second 128 board was absolutely covered with dust, and even had what looked like seeds and other natural bits of debris. Who knows what conditions these Macs were stored in. But that board did work despite the dust, so I grabbed the ROMs, cleaned them up a bit, and swapped them into the logic board of the non-working 128. Put that board back, fired it up and...
*bong*
with a sad mac code of 020400.. and a lot of stray pixels all over the screen. The sad mac code was fortunately readable but the numbers were missing several pixels. So it looks like at least one ROM from the 128 board was bad.. and in addition to that the sad mac code indicates that the RAM at G7 was bad.
Now it was time for desoldering.. I removed the G7 ram (an MT4264) and replaced it with a TI 4164 chip. I opted for the method recommended in the Pina book of clipping the leads off at the chip and removing them afterwards. Not sure what experience others had with this, but I don't think I had the right type of cutters for this job. Mine were a little too large and too blunt to effectively clip the leads off close to the chip. If anyone has any recommendations for good cutters for this, please let me know.
After adding this chip, the board went back in the Mac, turned on -
*bong* - Sad Mac 044120
-- 3 more chips to replace now, G11, G5, and F10. I replaced each of these, testing after each replacement, and things progressed as I expected - after replacing G11, the code was 040120. After replacing G5 - I had a momentary scare when I turned the mac on and instead of a regular bong and sad mac there was a distorted bong and a screen full of garbage, with the hint of a sad mac message in the middle. I refreshed the solder connections on the new G5 chip, tried again, and phew, all was well, with a sad mac of 040020.
Last chip to be replaced was F10. Replaced that, started again and -
** SUCCESS **! Regular screen, asked for a boot disk. From the external floppy, booted up system 1.1 and it worked!
So in total 4 of the DRAMS were bad, and one or both of the ROMs. I haven't gone back to figure out which one was the culprit. Looks like now to have both 128s running properly I'll need to find one or both ROMs.. or perhaps burn a replacement PROM. Does anyone have any experience with using currently available PROMS or EEPROMS for ROM replacement? I was looking into this for an Apple II+ repair at one point and it looked like the pinouts were different, but could be adapted with a special socket.
Anyway, thanks for all of the advice, and I'm glad the machine eventually worked. One more Mac liberated. Now I just need to find an easier way to get those bad RAMs off of the board, that part of the process took me way too long.
jsarchibald
Well-known member
Fantastic news! Glad to see it was repairable!
At least Apple gives you the codes needed to repair these machines, it is a godsend 25 years later.
At least Apple gives you the codes needed to repair these machines, it is a godsend 25 years later.
Mac128
Well-known member
Gubbish, congrats!
Before you do any more work with that unit powered on, make sure you check the voltage and adjust for optimal conditions. Having cleaned it up, it will give you a false sense of security, and could easily tax the aged and poorly stored components to a literal melt-down. This is especially true if you are going to keep testing with it. Turning the unit on is one of the more stressful functions you can perform, so it's no wonder that they often fail on startup more than any other time.
As for the ROMs, look forward to hearing if either of the originals now function, which now that the DRAMs have been restored, might actually work. Good trouble-shooting by the way. I presume you checked the ROM pins for corrosion and found none? Regardless, I can't say I'm surprised the large Apple silkscreened logo DRAM chips were bad. This is the most common failure in logic boards with those chips. This might explain why Apple got such a deal on them! Otherwise, I have found the logic board components to be quite robust. I am a bit surprised that the ROMs have gone bad, but like the DRAM Apple sourced those out to more than one manufacturer, like the CPU as well. So your particular ROMs could likewise suffer from some form of "bit-rot" especially if stored poorly. Since I have not yet heard an explanation for why this kind of failure occurs, I am free to speculate that environmental factors can contribute just as much as disuse. But what do I know.
Thanks for offering such a detailed path to recovery. It just goes to prove how easy it can be to recover these little guys. Since you are now running mixed DRAMs, I am quite interested in how the Mac operates once you get it completely back on it's feet and using it.
Before you do any more work with that unit powered on, make sure you check the voltage and adjust for optimal conditions. Having cleaned it up, it will give you a false sense of security, and could easily tax the aged and poorly stored components to a literal melt-down. This is especially true if you are going to keep testing with it. Turning the unit on is one of the more stressful functions you can perform, so it's no wonder that they often fail on startup more than any other time.
As for the ROMs, look forward to hearing if either of the originals now function, which now that the DRAMs have been restored, might actually work. Good trouble-shooting by the way. I presume you checked the ROM pins for corrosion and found none? Regardless, I can't say I'm surprised the large Apple silkscreened logo DRAM chips were bad. This is the most common failure in logic boards with those chips. This might explain why Apple got such a deal on them! Otherwise, I have found the logic board components to be quite robust. I am a bit surprised that the ROMs have gone bad, but like the DRAM Apple sourced those out to more than one manufacturer, like the CPU as well. So your particular ROMs could likewise suffer from some form of "bit-rot" especially if stored poorly. Since I have not yet heard an explanation for why this kind of failure occurs, I am free to speculate that environmental factors can contribute just as much as disuse. But what do I know.
Thanks for offering such a detailed path to recovery. It just goes to prove how easy it can be to recover these little guys. Since you are now running mixed DRAMs, I am quite interested in how the Mac operates once you get it completely back on it's feet and using it.
Sounds like a good idea to check the voltage conditions. Need to get myself a new multimeter - I had an old one which seems to have broken.
The ROMs seemed to be fairly corrosion free, although I'll check again next time I open the Mac up.
There were different logos on the two sets of ROMs, so it does seem like two different companies sourced them. I'll send some pictures of both sets in case anyone is interested.
Forgot to mention that I also tried the bad ROMs in the working 128 logic board, and it did not work - in fact it resulted in a slightly different error condition. With the bad roms in the otherwise working 128 board, I got a checkerboard pattern instead of vertical stripes. I'll check those roms back in the repaired board and see what I get.
Next steps will be to check if just one or both ROMs are bad. Also attempted to rehabilitate the seized-up internal floppy drive last night. Got the parts de-greased and moving again, but there seems to be something else wrong with the drive. The red LED does come on, but when disks are inserted there is just a mournful quiet chunk..... chunk... chunk.... sound and no movement. I'll look through the repair book again to see if this case is mentioned.
Does anyone happen to know the pinout for the 128 roms? I may look into what steps would need to be taken to get a modern-day PROM to work as a substitute.
Thanks again!
The ROMs seemed to be fairly corrosion free, although I'll check again next time I open the Mac up.
There were different logos on the two sets of ROMs, so it does seem like two different companies sourced them. I'll send some pictures of both sets in case anyone is interested.
Forgot to mention that I also tried the bad ROMs in the working 128 logic board, and it did not work - in fact it resulted in a slightly different error condition. With the bad roms in the otherwise working 128 board, I got a checkerboard pattern instead of vertical stripes. I'll check those roms back in the repaired board and see what I get.
Next steps will be to check if just one or both ROMs are bad. Also attempted to rehabilitate the seized-up internal floppy drive last night. Got the parts de-greased and moving again, but there seems to be something else wrong with the drive. The red LED does come on, but when disks are inserted there is just a mournful quiet chunk..... chunk... chunk.... sound and no movement. I'll look through the repair book again to see if this case is mentioned.
Does anyone happen to know the pinout for the 128 roms? I may look into what steps would need to be taken to get a modern-day PROM to work as a substitute.
Thanks again!
H3NRY
Well-known member
ROMs for a 128K Mac can be replaced with 27C256 EPROMs with pin 1 lifted out of the socket and jumpered to pin 28. (Programming pin needs to be tied to +5V for Read Only useage.) If you can get the part number (there were at least 3 different "64K" ROM versions), I may have an original chip to replace your bad one. Worst case, I can fire up the Apple II EPROM burner and burn a pair of 27C256es. This is the first case of a bad ROM chip I've heard of, but considering the age of those chips, I can't say I'm terribly surprised.
Vertical stripes with no "BONG" or error code usually means the CPU isn't running, and that usually is some sort of ROM problem, usually from an upgrade come loose, as has been mentioned. Kudos for excellent trouble shooting!
Vertical stripes with no "BONG" or error code usually means the CPU isn't running, and that usually is some sort of ROM problem, usually from an upgrade come loose, as has been mentioned. Kudos for excellent trouble shooting!
Just checked again, and it looks like the bad ROMs are 342-0220-A and 342-0221-A. The working ROMs are 342-0220-B and 342-0220-B.
H3NRY, thanks for the information about the 27C256's. Jumpering pin 1 to 28 seems like it wouldn't be too difficult.
With two different sets of ROMs, I guess I can't pinpoint the bad chip by replacing the low or high rom individually. But I do have a ROM reader circuit that I used for some Apple II+ ROMs around somewhere, I might be able to resurrect that to read off the contents of the chips and see which one is bad.
H3NRY, thanks for the information about the 27C256's. Jumpering pin 1 to 28 seems like it wouldn't be too difficult.
With two different sets of ROMs, I guess I can't pinpoint the bad chip by replacing the low or high rom individually. But I do have a ROM reader circuit that I used for some Apple II+ ROMs around somewhere, I might be able to resurrect that to read off the contents of the chips and see which one is bad.
H3NRY
Well-known member
I find looking in my box of old ROMs, a set of 342-0220/21 (no letter), a set of -As and a set of -Bs, so I guess I have both versions plus a possible third version. There's also a set of Beck-Tech 64K upgrade ROMS which support large memory up to 4MB. Question: will a set of -A ROMs work in a Mac that shipped with the -B version? I don't remember what the differences are (if I ever knew to begin with.)
I seem to recall that one set of ROMs revised only one of the two chips, though both got new letters. I believe that was one of the 128K (Mac Plus) ROM sets, though, and the fix had to do with booting SCSI. When I have time, I'll try to dump these ROMs assuming my ROM burner for the Apple II still works. It's been in the closet for at least 20 years. If I can get a good read, I'll post the raw files for the curious. I imagine the ROM files are already on the 'net someplace, since emulators need them. I'm not inclined to disassemble and trace the code myself. Did that long ago and it was a lot of work.
I seem to recall that one set of ROMs revised only one of the two chips, though both got new letters. I believe that was one of the 128K (Mac Plus) ROM sets, though, and the fix had to do with booting SCSI. When I have time, I'll try to dump these ROMs assuming my ROM burner for the Apple II still works. It's been in the closet for at least 20 years. If I can get a good read, I'll post the raw files for the curious. I imagine the ROM files are already on the 'net someplace, since emulators need them. I'm not inclined to disassemble and trace the code myself. Did that long ago and it was a lot of work.
Mac128
Well-known member
I too have a 128K which has a 342-0220-A/0221 with no letter - however, it does say "REV A" next to the copyright date. It happens to be on my early 13th week, completely original, unaltered 128K. So this is either a mixed ROM set, reflecting an early revision in the product cycle, or an early method to represent the "-A". Do yours have the words "REV A" next to the copyright date?
As for the ROM dump, I sent a -B disassembly file to Paul Pratt to compare to his -A ROM set, and he indicated minor changes. I did not think to send him the 0221 REV A ROM, however. Nevertheless, the 1984 copyright date relates to the Sony drive stepper motor update. Both ROMs will work in either MAC. However, since the fix pertains to the newer 400K drive revision, newer drives are incompatible with the -A chips. The -B chips are backward compatible.
As for the ROM dump, I sent a -B disassembly file to Paul Pratt to compare to his -A ROM set, and he indicated minor changes. I did not think to send him the 0221 REV A ROM, however. Nevertheless, the 1984 copyright date relates to the Sony drive stepper motor update. Both ROMs will work in either MAC. However, since the fix pertains to the newer 400K drive revision, newer drives are incompatible with the -A chips. The -B chips are backward compatible.
Similar threads
