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IIfx powers on, but no chime and no video


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Hello everyone,

 

I'm currently trying to bring an old IIfx back to life.

 

It powers on using both the back switch and an ADB keyboard but goes no further. The speaker makes a little popping sound (I assume this means it's getting power) but doesn't chime. There is no video on my known-good original Mac display, using either of the NUBUS cards I have kicking around. NUBUS is getting power however, because my Ethernet card is happily flashing green on power-on.

 

Here's what I have done so far:

- New batteries.

- Replacement of the electrolytic condensators with tantalums (using the very handy second set of pads - thanks designers!). I also replaced the axials. I did not swap out the existing tantalums (C6, C7 and C8).

- Trace repair at the intersection of C7, C8 and C9. Corrosion had dug through the copper. I tested the fix for continuity and things are OK now.

- PSU voltage testing at the motherboard. The yellow wire gives me a steady 12v, red gives me a steady 5v and things seem fine.

- Tried a ROM-inator II instead of the stock ROM. No dice.

- I've slowly gone through the motherboard with a microscope to find further weirdness, but nothing is jumping at me.

 

Stray observations:

- Hitting the reset switch also makes a little clicking sound. The debug switch doesn't.

- It's a revision B motherboard.

- After running for a while, the 68030 is warm to the touch (does that actually mean it's doing something?).

 

I'm a little lost at to what to try next. It's not my first recap (3 successes under my belt so far - woohoo) but maybe I've messed something up. I've tested for continuity on every cap I replaced and they seem fine. Is this a sufficient test?

My understanding is that the ROM calls take place after the initial chime (death or happy). Is this correct and can I therefore rule out a problem with the ROM?

I'm looking at the Bomac schematics but it's the proverbial needle in the haystack. Where to start?

 

Would anyone have an idea as to what to try? I'm a little lost for ideas.

 

Thanks everyone.

 

-- Edit: it's the reset switch that makes a little sound, not debug.

Edited by WombatPredator
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I'm having the same problem...although at first I would get a bong and now I do not since I ended up having much more extensive trace damage than I could see until I put it under a microscope.  The areas toned out continuity fine but looking closer and barely scraping there were several very weak traces barely holding on.  Mine were D6 to via, D6 to C42, D5 to UJ18.  UI18 and UJ18 also had some corroded legs so I suspect that I may need to remove them and clean underneath, and possibly replace them.  I had a continuity issue somewhere on pins 1-7 of UI18 possibly - not sure if it was a fluke or I read the startup circuit schematic wrong.

 

So I suggest taking a very close look with at least a magnifying glass.  And then use Gamba's IIfx startup circuit schematic to double check the logic chips: macIIfxsch.GIF (726×536) (vintageapple.org) if you haven't already

 

Edit: I missed the part where you were already using a microscope.  But concentrate on that area and do some gentle scraping on anything that looks even slightly discolored or dirty

 

Edited by JRotar
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On 3/29/2021 at 7:29 AM, JRotar said:

I'm having the same problem...although at first I would get a bong and now I do not since I ended up having much more extensive trace damage than I could see until I put it under a microscope.  The areas toned out continuity fine but looking closer and barely scraping there were several very weak traces barely holding on.  Mine were D6 to via, D6 to C42, D5 to UJ18.  UI18 and UJ18 also had some corroded legs so I suspect that I may need to remove them and clean underneath, and possibly replace them.  I had a continuity issue somewhere on pins 1-7 of UI18 possibly - not sure if it was a fluke or I read the startup circuit schematic wrong.

Thank you very much for your reply. I'll take a closer look in that neighborhood. I may have overlooked some of those legs.

 

The hugeness of the IIfx motherboard makes it difficult to maneuver under a microscope without constantly bumping into the boom stand. It's sometimes tricky to look at something under different angles, and things might end up unnoticed.

 

And thanks for drawing my attention back to Gamba's diagram. I had looked at it in the past but it's now obvious that, judging by the symptoms I'm experiencing, the issue lies somewhere there.

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20 hours ago, FunnymanSE30 said:

Is there any leaking caps on the video card? The Apple high resolution display card in my iifx had a few, also a burnt ceramic capacitor. Does it chime with no video card installed?

 

No leaking cap that I can see. But good thing to check once I get there!

 

Right now, I'm aiming for the death chimes. I'm running the board without RAM, without ROM* and without any card. The only things plugged in are the speaker, the batteries and the PSU (obviously).

 

* It's my understanding that the machine chimes when it's done powering up and before it looks at the ROM but I might be mistaken. I'm looking at page 244 of the "Guide to the Macintosh Family Hardware 2nd Edition" (it's on archive.org) but I don't see mention of chimes, which is a shame because it's a useful goal post in the boot process.

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21 hours ago, WombatPredator said:

It's my understanding that the machine chimes when it's done powering up and before it looks at the ROM

 

Well, the code to produce the chime and the chime itself have to be somewhere :-) they're both in the ROM, so no ROM, no chime.

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20 hours ago, cheesestraws said:

 

Well, the code to produce the chime and the chime itself have to be somewhere :-) they're both in the ROM, so no ROM, no chime.

<smacks forehead>

Of course. And the fact that the ROM-inator II has a custom chime should have been a clue to that. Thanks for pointing it out!

 

Back to testing with the ROM in then, and to including the ROM has a potential cause for my troubles.

 

I've been redoing some continuity testing around the areas pointed out by JRotar above and, previously, I was only paying attention to the beep (easier when your eyes are glued to a microscope). However, a couple of traces take longer to beep and show 5 Ω (where most of them are at 0.3 Ω or less). I'll reflow them and report back.

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Well, reflowing the weird traces didn't help. And after another thorough cleaning of the board with IPA and a toothbrush, still nothing. I've also been checking Gamba's diagram and checking every connection in the startup circuit and nothing seems amiss there either. Corrosion seems minimal.

 

To illustrate the depth of my despair, I got pretty excited when I found a flake of flux straddling two legs on a chip :p

 

I'm starting to wonder if I should start desoldering chips in the vicinity of the old caps, in case corrosion got underneath (although it seems unlikely judging by the rest of the board).

 

 

Once I have batteries in, a ROM chip, a connected speaker and the PSU delivering stable juice, I should have everything in place for a chime, correct?

 

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The trace repair at C7, C8 and C9 makes me wonder if there's more damage over there or under anything around there.  On mine I tried to solder a larger cap at C9 but messed it up which gave me instant startup...so that's not your problem, but maybe a good idea to reflow the ones you replaced.  I replaced C9 with a smaller one and that stopped the instant startup.

 

Have you replaced the radials?  My board had leakage from the radials as well around the startup circuit but not by the power supply connector.

 

I still think it might be a good idea to replace UI18 and UJ18 since there's a lot of gatekeeping going on inside those chips. I've seen on other posts with a IIci where they had no response from the system but replacing similar logic chips fixed it. 

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23 hours ago, JRotar said:

The trace repair at C7, C8 and C9 makes me wonder if there's more damage over there or under anything around there.  On mine I tried to solder a larger cap at C9 but messed it up which gave me instant startup...so that's not your problem, but maybe a good idea to reflow the ones you replaced.  I replaced C9 with a smaller one and that stopped the instant startup.

 

Have you replaced the radials?  My board had leakage from the radials as well around the startup circuit but not by the power supply connector.

 

I still think it might be a good idea to replace UI18 and UJ18 since there's a lot of gatekeeping going on inside those chips. I've seen on other posts with a IIci where they had no response from the system but replacing similar logic chips fixed it. 

 

Thank you for the suggestions. C7-C9 is indeed the location where noticeable damage was noticed and I may have missed something there. And I'll try to reflow the new ones. Would you know what UB16 (a black cube with 4 metallic lines running across its top) is? I wonder if something oozed underneath.

 

I have replaced the radials. I don't think they were leaky but I did it anyway. I'll re-check those too.

 

And I dread replacing UI18 and UJ18 a little. I haven't replaced a multi-legged thing yet :)

 

I wonder if I should get a logic analyzer (I was shocked by how cheap they were these days) to take a look at the signals. This guy is describing something very similar on a Mac II, and the Bomac schematics show that the sound chips play the same role in the IIfx (they are UP2 and UP3, on page 8 of the IIfx document). When I press the reset switch, I do see a voltage change on pin 7 of both chips. Maybe something is wrong with the clock here too?

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On 3/30/2021 at 7:05 AM, WombatPredator said:

And I dread replacing UI18 and UJ18 a little. I haven't replaced a multi-legged thing yet

I hear ya.  I got a cheap hot air station from Amazon to help.  Practiced on a bad board...got to the board I was trying to fix (Not the IIfx luckily) and I ripped a couple pads but I was also getting impatient.  I find that if I use braid on the pins to remove as much as possible and then add hot air they usually slide right off in like 30 seconds.

 

Edit:  Actually you could also try braid on the pins and then just re-solder, especially if there was corrosion around the chips.  Could just be a bad connection.

 

Now this sounds really stupid, but it just hit me.  The speaker on my IIfx was bad and the glue around the edges of the speaker cone was all gummy so maybe try a different speaker and you might be getting a bong or chimes of death but just can't hear it. 

Edited by JRotar
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On 3/31/2021 at 8:07 AM, JRotar said:

I hear ya.  I got a cheap hot air station from Amazon to help.  Practiced on a bad board...got to the board I was trying to fix (Not the IIfx luckily) and I ripped a couple pads but I was also getting impatient.  I find that if I use braid on the pins to remove as much as possible and then add hot air they usually slide right off in like 30 seconds.

 

Edit:  Actually you could also try braid on the pins and then just re-solder, especially if there was corrosion around the chips.  Could just be a bad connection.

 

Now this sounds really stupid, but it just hit me.  The speaker on my IIfx was bad and the glue around the edges of the speaker cone was all gummy so maybe try a different speaker and you might be getting a bong or chimes of death but just can't hear it. 

Thanks for the tips on the desoldering. Sounds feasible / terrifying.

 

I also have a cheap air station* (huge time saver for the 14+ caps of the IIfx) so I could definitely try the removal that way.

But I'll try your second idea first, I think :) 

 

And I assumed that the speaker was good because plugging in headphones gave me the same popping sound as the speaker. But thanks to your comment, I now realize that it doesn't really prove anything because I don't recall if the chimes are played in the output jack. It could still be the speaker, or the whole sound circuit that's gone bad (and the traces for the headphones are right around my nemeses C7-C9...).

 

Thank you so much for following-up on this. It really helps putting things in perspective.

 

* Which came free with a new stressful task: protecting all the plastic things in the vicinity of the hot blast by carefully arranging makeshift heat shields like a crazy person

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On 3/31/2021 at 6:37 AM, WombatPredator said:

don't recall if the chimes are played in the output jack

Chimes do come through the headphone jack....I just double checked on my good IIfx.

 

I've seen a few people mainly with IIci and IIcx that removing and resoldering the logic chips fixes it so definitely try to at least remove as much solder and re-do them and see if that helps.

 

I bought cheap Capton tape off Amazon and it really does work: High Temp Tape, ELEGOO 4 Pack Polyimide High Temperature Resistant Tape Multi-Sized Value Bundle 1/8’’, 1/4’’, 1/2’’, 1’’ with Silicone Adhesive for Masking, Soldering etc.: Amazon.com: Industrial & Scientific

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On 4/1/2021 at 2:17 AM, JRotar said:

Chimes do come through the headphone jack....I just double checked on my good IIfx.

 

I've seen a few people mainly with IIci and IIcx that removing and resoldering the logic chips fixes it so definitely try to at least remove as much solder and re-do them and see if that helps.

 

I bought cheap Capton tape off Amazon and it really does work: High Temp Tape, ELEGOO 4 Pack Polyimide High Temperature Resistant Tape Multi-Sized Value Bundle 1/8’’, 1/4’’, 1/2’’, 1’’ with Silicone Adhesive for Masking, Soldering etc.: Amazon.com: Industrial & Scientific

Thanks for checking the headphone jack! That really helps!

 

I've ordered some tape as you recommended, that should diminish the stress levels :)

 

I've also received a little logic analyzer. I picked a 200 MHz model because I need it to keep up with the wicked fast 40 MHz of the IIfx, and the recommendation seems to be that the analyzer should run 4x or 5x faster than the thing being analyzed (to ensure that nothing is missed). A lot of these analyzers seem targeted at Arduinos and serial ports and, let's face it, we're looking at the quickest piece of hardware this side of 1989, here.

So when I need to select a piece of cheap equipment with very approximative instructions, I spare no expense.

 

Hopefully, this will tell me whether the clock is running properly. Considering how early in the process the machine seems to stall, it's not even a given that it is running.

 

After that, I will be out of excuses and I will attempt the resoldering of UI18 and UJ18 you're suggesting :)

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On 4/2/2021 at 7:30 AM, WombatPredator said:

I've also received a little logic analyzer.

Let me know how it works!  I've been thinking about getting one but have no idea where to start.

 

On 4/2/2021 at 7:30 AM, WombatPredator said:

Considering how early in the process the machine seems to stall, it's not even a given that it is running.

That's exactly how I feel about mine too, even when it did chime.  Just felt like something wasn't giving it the "go ahead" to continue.

 

On 4/2/2021 at 7:30 AM, WombatPredator said:

After that, I will be out of excuses and I will attempt the resoldering of UI18 and UJ18 you're suggesting

I think I need to try that too...and get more ballsy about doing the real trace repairs I need to do

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On 4/3/2021 at 8:02 AM, JRotar said:

Let me know how it works!  I've been thinking about getting one but have no idea where to start.

 

I have received the logic analyzer and I've been able to poke around a little with it. Once you get your head around the basics, it's quite straightforward and, so far, it's been like shining a flashlight all over the dark corners of the board. I get the feeling that, instead of my current approach of "let's take a wild guess at what could be wrong and hope I find something", I should be able to methodically start ruling things out and pinpoint the source of my troubles.

 

So, the model I got is an InnoMaker LA2016 (which seems to exist under a bunch of different brands, including "Kingst"). It's by no means the cheapest (you can find an analyzer for less than 20 bucks!), the most compatible (it's barely supported by the sigrok project which aims to be the end-all be-all of the software side of such tools) or the sexiest (that would be the ones made by Saleae). It does however check the boxes I had, considering I'm trying to fix an old Mac and not building an Arduino project:

  • It samples at 200 MHz (200 million samples per second). As mentioned previously, the consensus is that you need to be able to sample at a frequency of 3x or 4x the thing you're sampling. Otherwise, you could be missing something important if it happens between samples. The IIfx runs at 40 MHz, and so 200 MHz seemed a good choice. There's a model that samples at 500 MHz but it's $100 more.
  • It has 16 channels (it can sample 16 things simultaneously). A lot of its competitors only have 8.
  • Its software has a demo mode and, while it's never going to win a design prize, it does the job, supports the major platforms and even runs in Mac OS Big Sur without having to sign anything in blood (just the usual right-click-on-the-icon-and-select-"Open" magical incantation that needs to be done to things that are blocked by GateKeeper). I just plugged the analyzer in a USB port, it went "oh hi there" and everything was working.
  • In my future, I can see myself debugging serial protocols. To help with this, it comes with a bunch of decoders to help make sense of the signal. In other words, I should be able to plug some of its probes into the serial port of an old Mac, tell the analyzer "this is a UART thing, please decode it" and I should see the actual bytes appear.

Armed with this, I decided to see if I could put to rest the question "Is something wrong with the sound hardware and is this why I don't hear a chime or is there something else".

 

On the last page of the Bomarc document for the IIfx, I can see that pin 11 of the sound chips are connected to the speaker (and the output jack) so I put a probe on both of these, and connected the ground probe to... ground:

 

350449378_Soundtest.thumb.jpeg.b135190b2c41e01b699d5a18a9c02699.jpeg

 

I started the capture, started the machine, and 10 seconds later I had this (purple is pin 11 of UP2 blue is pin 11 of UP3):

General.thumb.png.20492753bb621e85e9c74d71b4943c85.png

Ok, so something happens in the first milliseconds, then it drops to 0, then back to 1 afterwards.

 

I zoomed in on the "something happens":

101375957_ROMin.thumb.png.05fb6f317da987a9f324f80792e15a10.png

Ok... Maybe it's noise.

 

Then it hit me that I could also put a probe on the speaker connector itself (in green - note that the zoom level is different):

1659944914_ScreenShot2021-04-04at12_56_13.thumb.png.9516367be3112b1e826d92d01b005c3e.png

This is pretty much the point where I got excited. Not because I had found the solution to my problem, but because I could measure what I could only feel before: there's a popping sound in the beginning of the boot sequence (caused by the sound chips), then the sound chips go high and the speaker remains silent.

 

I then tried without the ROM chip and the exact same pattern emerged (I'm not including screenshots, they're the same).

 

So, it's not the sound. The sound circuit is fine, it just doesn't have a sound to play. My next step will be to take a look at the ROM.

 

I realize my poking around (and choice of hardware) is probably funny / obvious to some but if, like me, you feel like you're in the dark as to what could be wrong with your machine, I think this is a tool that can really help.

 

I can't wait to dig further.

 

Edited by WombatPredator
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On 4/5/2021 at 1:48 PM, WombatPredator said:

I realize my poking around (and choice of hardware) is probably funny / obvious to some but if, like me, you feel like you're in the dark as to what could be wrong with your machine, I think this is a tool that can really help.

This forum seems friendly to beginners at least.  Plus there's no harm if it helps you figure out how it works, and it certainly will helps others, myself included.

 

It looks really powerful for the price!  I was looking at simple high-low probes but this looks so cool that I may have to get it.

 

I'm really curious if you test out the logic chips with this to see if there's any fault on them!

 

Also, this thread on a IIci has some interesting takeaways about the Qx transistors How I resolved my IIci soft power problems (half bong and instant shutdown when switched on) - Mac II, Quadra & Centris - 68kMLA Forums  Not completely the same but interesting about removing one to force a power on

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On 4/5/2021 at 9:48 PM, WombatPredator said:

I realize my poking around (and choice of hardware) is probably funny / obvious to some but if, like me, you feel like you're in the dark as to what could be wrong with your machine, I think this is a tool that can really help.

 

Being able to see what's going on is a big thing, and enables learning new things in a way you can't when you're just guessing.  The more people realise these tools are available and learnable the better :-)

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this might seem really simply - but have you tried pushing the ROM stick into the slot? My IIx has a bad ROM SIMM Slot and often won't make contact with the SIMM (Especially the modern ones which tend to be a thinner 1.2mm PCB whereas the original ones where 1.27mm) when it is not making contact I get the exact same symptoms as you are getting here

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On 4/7/2021 at 2:03 AM, JRotar said:

It looks really powerful for the price!  I was looking at simple high-low probes but this looks so cool that I may have to get it.

 

I think that for the specific use cases of the denizens of these forums, it has a very good price / usefulness ratio. This little box should be able to happily sample the fastest 68k Mac of all times (the 840AV), which is a 68040 running at 40 MHz. Also, it's being actively reverse-engineered and integrated in the sigrok project (specifics for this model are here) which means that alternative (and potentially better) interfaces exist, and that it will remain useful in case its manufacturer drops it.

If you can afford it, I think it will cover a lot of your needs for a long while.

 

 

On 4/7/2021 at 2:03 AM, JRotar said:

I'm really curious if you test out the logic chips with this to see if there's any fault on them!

 

As soon as I have some free time, I'll take a look.

 

On 4/7/2021 at 2:03 AM, JRotar said:

 

Also, this thread on a IIci has some interesting takeaways about the Qx transistors How I resolved my IIci soft power problems (half bong and instant shutdown when switched on) - Mac II, Quadra & Centris - 68kMLA Forums  Not completely the same but interesting about removing one to force a power on

 

I saw that! Very interesting indeed! I didn't make the connection with my problem but it's definitely something to keep in mind. The startup circuits on the II series seem fairly similar (and a little convoluted).

 

 

 

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On 4/7/2021 at 2:36 AM, max1zzz said:

this might seem really simply - but have you tried pushing the ROM stick into the slot? My IIx has a bad ROM SIMM Slot and often won't make contact with the SIMM (Especially the modern ones which tend to be a thinner 1.2mm PCB whereas the original ones where 1.27mm) when it is not making contact I get the exact same symptoms as you are getting here

 

I didn't think of that. I've been trying a couple of ROM SIMMs with the same results, and close inspection of the slot led me to believe that it was fine (no corrosion, nothing bent). But I didn't really consider that the problem might be simply mechanical. I'll take another look. Thanks for the idea!

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