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IIfx - Chime, but not video and no boot?

macgyver84

New member
Hi,

for over a decade, I have owned a spare IIfx logic board (bare board, not in a case). Seems like it had not been worked on before, original (electrolytic!) caps. It chimed, but did not show any video and did not boot. A recap with tantalums and a thourugh board wash has changed nothing back then, so it sat in the closet for years.

I decided to give it another go now, however I haven't had any success yet. I have another working IIfx and tried the board with its RAM modules and the ROM SIMM, good known graphics card and PSU, so the fault must be definitely with the board. The PCB is looking pretty good with only minimal signs of corrosion on some traces/vias. All of them turned out to be fine when scraped/measured. I already checked lots and lots of traces and vias, have also removed ICs near caps to look under them, so far I have not found anything wrong - there was no need to repair any trace yet, so no smoking gun so far.

In detail, when I turn the power on (power circuit works fine), it immediately gives the "good" chime, then after maybe 2...3 seconds delay there is a faint "pop" in the speaker, then nothing. No video, no nothing. Pushing the interrupt button will give the death chime, other than that I failed to get any reaction out of this board. No try to boot from floppy, no ejecting a non bootable floppy, nothing.

Are there any "common" faults associated with that on the IIfx? Any ICs I might try to remove, like the SWIM chip, any other hints like common bad traces I might have overlooked? I feel like it is almost working and hate to give up. It is possible that this board was removed from a computer a long time ago and might have died of other causes than leaking caps... :(

Thanks a lot! :)
 

hyperneogeo

Well-known member
I find a lot of faults on the IIFX are because of the ram/rom simm sockets. Put the bare min ram in (4 ram sticks) and the rom stick in, then push on them toward the contacts and see if you get anything. Also it might be good to invest in a rominator ii as it speeds up boot time.

I've had bad contacts on ram that produce what you are saying.

Also might be good to post a pic of the board.
 

macgyver84

New member
I did some more work on it today and found a cracked inductor (no continuity) near the Nubus clock circuitry. I replaced that, tested the board and got video! Grey screen, mouse pointer. Hooray! Oh, wait, mouse pointer is frozen. Hit reset: Chime, no video. Powered it down, got a floppy drive to test further (maybe I can get it to boot?), got the grey screen again, mouse pointer moves for a bit, freezes. After that, I tried many many times and didn't get any video again, so back to square one: Chime, pop, no video.

Funny enough, it even gives the happy chime when I remove a single RAM module, which should result in a sad chime if I remember correctly. I am not sure what is going on, will maybe try to get it into serial diagnostic mode. Sadly I don't have a Techstep... :( Any error code which would point in the direction to go would really help. Does anybody have experience using the serial diagnostics?


This is all I read about it so far, maybe somebody has experience with this? Will try to hook it up to a terminal and see what I get.
 

macgyver84

New member
I found it. It seemed temperature dependent, since the board would always come up to the mouse pointer when left for a while without power, but never when pressing reset or doing a quick re-power up. I used cold spray to check on the ICs, and hooray, when I spray UL8 (16L8 PAL) with cold spray and hit reset, the machine comes up every time and as long as I keep it cold, it will boot from floppy and work flawlessly. When I stop cooling it, the machine will lock up within 30 seconds.

So far the good news. I guess nobody has the equations of this PAL, so I will probably have to hunt down an 16L8 from a donor board?

Thanks a lot!
 

Bolle

Well-known member
Code:
;$GALMODE MEDIUM

chip IIfx_UL8 GAL16V8

i1=1 i2=2 i3=3 i4=4 i5=5 i6=6 i7=7 i8=8 i9=9 GND=10 i11=11
o12=12 f13=13 f14=14 nc=15 f16=16 f17=17 nc=18 o19=19 VCC=20

@ues 0000000000000000
@ptd unused

equations

/o19 = /i2 * i11
     + /i4
     + /i3
     + /i1
     + /f17
o19.oe = vcc

/f17 = /i2 * i11
     + /i4
     + /i3
     + /i1
f17.oe = /i6

/o12 = /i9
     + /i8
     + /i5
     + /f16
o12.oe = vcc

/f16 = /i9
     + /i8
     + /i5
f16.oe = /i6

/f13 = vcc
f13.oe =  i7 * /f14

/f14 = vcc
f14.oe =  /i7 * /f13

Confirmed working ;)
 
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