Acquired a IIfx (yay!) Issues (boo!)

[mst3k]

Finally got my mitts on a IIfx.
It works! Almost.

No floppy function at all.
Checked the voltages at the PSU connector with a multimeter. Good.
Checked for obvious trace damage. None.
Tried a known good cable. NaDa. Tried another known good cable. Nothing.
Tried a known good drive. Nope. Tried another known good drive. Negatory.
Checked the pins on the two board connectors for damage and voltage. No damage and 12 volts on the top right pin (not sure how they are numbered) on both cable connectors. No weirdness on the other pins.
The machine boots. It chimes. It runs a hard disk or my Zuluscsi without issue.
I tried a Rominator ROM just for the heck of it. Nothing.
I tried my Floppy Emu. Nothing.

Any suggestions what to try next?

Thanks in advance!

 

[mst3k]

To clarify, the Rominator worked fine. It's presence had no effect on the floppy drive malfunction.
Also, Floppy Emu shows no signs of life at all on either one of the connections. It works fine on my other Macs.

 

[mst3k]

OK. Went through everything again.
I'm only getting 4.4 volts on the white in, which I believe is part of the FDD power (I can't find an FX PSU pinout).
Everything else works fine.
Recap the power supply? The power supply is an Apple part #699-0393 Model CR45S.
Is there a modern replacement?
Thanks

 

[Callan]

Don't know much about the iifx. Saying that.... it sounds like everything else is working except the floppy's 5v. I know everyone says it, but since you didn't address it in your description. Have you replaced the electrolytic caps on the motherboard? A bad cap could be pulling down your 5v line. They're going to have to replaced regardless since they're all leaking / about to leak.

 

[volvo242gt]

^IIfx has only two electrolytics that are present on some of the boards. The remaining boards already had tantalum caps on them. Attached is a pic of one of the electrolytic cap IIfx boards.

 

[mst3k]

^IIfx has only two electrolytics that are present on some of the boards. The remaining boards already had tantalum caps on them. Attached is a pic of one of the electrolytic cap IIfx boards.

View attachment 71411

Thanks Volvo 242. (The IIci is working great BTW!).
Thanks too, Callan.
There are two electrolytics. one at C9 and one at C24 on my board. I'll replace both. But...
I'm only getting 4.4v on the white wire at the connector to the logic board. Wouldn't that indicate an issue at the PSU?
I've torn apart the PSU again and found some suspicious yellow goo underneath...
I'm planning on pulling the caps and checking, replacing as necessary and reflowing the harness wires while I'm at it.
I thought I'd lucked out with a working IIfx but I guess nothing is ever straightforward in MacLand.

 

[3lectr1cPPC]

IIfx has only two electrolytics that are present on some of the boards. The remaining boards already had tantalum caps on them. Attached is a pic of one of the electrolytic cap IIfx boards.

All tantalum and the configuration you describe are the most common but they can come with any mix of either type, or even all electrolytic. Not the case here from the sound of it but I thought I'd clarify that anyway.

 

[Callan]

Your welcome!
Yeah. I would replace all the electrolytics (power supply and motherboard). Only reason i said the motherboard first is because you said everything else was working fine. It only takes one bad cap to pull a line down. I would replace all electrolytics in the system and clean the board before I started doing any troubleshooting.

 

[mst3k]

OK. Replaced the two caps on the logic board and all of the caps on the PSU (I left the two largest ones) and now I have a whopping 4.46 volts on my sick line. Everything works as before. Machine boots, HDD works, ZuluSCSI works, etc. Just no FDD.
Where else do I look to find my missing 1/2 volt?
The floppy connector still won't power a drive, but if I hook a drive up and throw a disk in, I get a message on the desk top that the disk needs initializing. If I select initialize, nothing happens on the drive side (no noise, no spinning, no nothing) and after about 20 seconds it says cannot initialize disk and the system freezes. I think that means the drive is talking, but isn't getting enough juice to function.
I tried the Floppy Emu again, but I get nothing. 4.46 volts not enough?
Or maybe there is something else haywire?
Anyway. I've exhausted my junior troubleshooter attempts and was hoping someone with more brains and experience could point me in a direction...
Thanks

 

[Callan]

Probably a little above mine too, but just to check.How is the 5v on other places on the board? Is it just low at the floppy drive? Are you testing the voltage at the drive, header pins, or at the inductors that feed the drive? Is the low voltage with the drive plugged into the board? If so what does it read without the drive plugged in. Are we chasing a red herring?

 

[mst3k]

Probably a little above mine too, but just to check.How is the 5v on other places on the board? Is it just low at the floppy drive? Are you testing the voltage at the drive, header pins, or at the inductors that feed the drive? Is the low voltage with the drive plugged into the board? If so what does it read without the drive plugged in. Are we chasing a red herring?

Thanks Callan.
Voltage is being checked at the PSU connector.
The voltage doesn't change with the FDD plugged in or unplugged. Stays at 4.46v.
I'm not sure how to check the voltage at the drive with it plugged in?
Anyway, thanks again for the help.

 

[Callan]

If your getting 4.46 at your 5volt rail for the whole board I'm surprised everything but your floppy is working. Something is pulling your rail down or your power supply isn't able to supply the current needs of the board. Iifx expert anyone?

 

[mst3k]

I barely qualify as a beginner, but it seems weird to me too.
I've tried my Apple external CDROM and it works and will boot the machine. It has it's own power, but no issues.
I just assumed that the power supply is the culprit. I don't have a duplicate PS to try, but I'm looking for one.

 

[mst3k]

If your getting 4.46 at your 5volt rail for the whole board I'm surprised everything but your floppy is working. Something is pulling your rail down or your power supply isn't able to supply the current needs of the board. Iifx expert anyone?

Decided to use brute force method. I've managed to find another power supply and will try a substitution.
Worst case, I have two power supplies. It's supposed to be here Saturday.

 

[nyef]

Looking at my IIfx, the white PSU wire is pin 15, and that's the line that you use to jumpstart the supply if there's something wrong with the startup circuit.

Case to pin 1 (yellow): 11v9
Case to pins 2, 3, 4, 5, and 6 (red): 5v13 (+/- 0.01)
Case to pins 7, 8, 9, 10, 11, and 12 (black): about 10 millivolts
There is no pin 13
Case to pin 14 (blue): -11v95
Case to pin 15 (white): 4v40

I don't think that the white wire voltage is your problem... unless your PSU uses different wire colors than mine does.

 

[mst3k]

Looking at my IIfx, the white PSU wire is pin 15, and that's the line that you use to jumpstart the supply if there's something wrong with the startup circuit.

Case to pin 1 (yellow): 11v9
Case to pins 2, 3, 4, 5, and 6 (red): 5v13 (+/- 0.01)
Case to pins 7, 8, 9, 10, 11, and 12 (black): about 10 millivolts
There is no pin 13
Case to pin 14 (blue): -11v95
Case to pin 15 (white): 4v40

I don't think that the white wire voltage is your problem... unless your PSU uses different wire colors than mine does.

Thank you for the voltages! I just assumed (a mistake) that pin 15 (white wire) should be 5v.
The rest of your voltages match mine +or-.
Brings me back to square one. There seems to be some communication with the floppy but it just acts like there is not enough juice to function.

 

[nyef]

Okay, next phase is to check the internal floppy connectors, J16 and J17. Pins 14 and 20 shouldn't be connected to each other (20 is a no-connect generally, and 14 is drive select), but the others should show continuity (though you might have trouble measuring that for the odd-numbered pins, those are all power and/or ground). All of the even-numbered pins (again, except for pin 20) should have continuity to UC10, the SWIM chip, mostly to the side nearer the RAM slots, but floppy connector pins 14 should continuity to different points on the side next to UC8, close to the back of the machine. Next, power-up and test the voltages. Pins 19, 17, 15, and 13 should show 12v, pin 11 should show 5v, and pins 7, 5, 3, and 1 should show ground. Some sources say that pin 9 should be 5v, but others say no-connect. I get nothing on pin 9 for my hardware.

 

[mst3k]

Okay, next phase is to check the internal floppy connectors, J16 and J17. Pins 14 and 20 shouldn't be connected to each other (20 is a no-connect generally, and 14 is drive select), but the others should show continuity (though you might have trouble measuring that for the odd-numbered pins, those are all power and/or ground). All of the even-numbered pins (again, except for pin 20) should have continuity to UC10, the SWIM chip, mostly to the side nearer the RAM slots, but floppy connector pins 14 should continuity to different points on the side next to UC8, close to the back of the machine. Next, power-up and test the voltages. Pins 19, 17, 15, and 13 should show 12v, pin 11 should show 5v, and pins 7, 5, 3, and 1 should show ground. Some sources say that pin 9 should be 5v, but others say no-connect. I get nothing on pin 9 for my hardware.

Thanks nyef!
I really appreciate the guidance.
I'll follow that troubleshooting list as soon as I get home and let you know how it goes.
Again, many thanks!

 

[mst3k]

Okay, next phase is to check the internal floppy connectors, J16 and J17. Pins 14 and 20 shouldn't be connected to each other (20 is a no-connect generally, and 14 is drive select), but the others should show continuity (though you might have trouble measuring that for the odd-numbered pins, those are all power and/or ground). All of the even-numbered pins (again, except for pin 20) should have continuity to UC10, the SWIM chip, mostly to the side nearer the RAM slots, but floppy connector pins 14 should continuity to different points on the side next to UC8, close to the back of the machine. Next, power-up and test the voltages. Pins 19, 17, 15, and 13 should show 12v, pin 11 should show 5v, and pins 7, 5, 3, and 1 should show ground. Some sources say that pin 9 should be 5v, but others say no-connect. I get nothing on pin 9 for my hardware.

OK. I had a chance to run through your guide.
The continuity to UC10, SWIM, is good as you outlined. I checked both connectors and got nice, loud beeps to UC10.
Voltage is another matter and I think you may have identified my problem. I just don't know how to fix it.
Pins 19, 17, 15, and 13 all show 12v. However, Pin 11 shows less than a volt and Pin 9 is even less.
The grounds all seem OK.

Any ideas on why Pin 11 is not getting the correct voltage?

Thanks again for the help.

 

[mst3k]

I should say too, that both floppy connectors are showing the same voltages.
The problem apparently isn't in the connectors themselves.