Mac IIsi with white screen, no sound, not booting

[BEU]

I got this Mac IIsi a year ago. Removed the battery and all caps then. Didn´t test it before that. Now I have started to get it working.  All caps are replaced with tantalums, new axial caps.
When I turn it on, the fan is working, HD is spinning. The screen is white with no mouse pointer. Only a click from the speaker but no other sound. The PSU is fine, I have also tested with o PSU from a working Mac IIci, same result. No RAM SIMMS, no ROM SIMM. pin W1 is enabled.  I guess the IIsi should boot with the RAM on board. I have checked several times for corroded traces but not found any . Also checked the new tantalums for correct capacitans. The speaker is OK. Same result without HD and floppydrive.

I have read "Troubleshooting Your Macintosh"  by Douglass High
page 85:

"Hardware initialization
A typical Macintosh hardware initialization consists of the following events:
1. Power is applied to the system.
2. The power supply establishes the appropriate voltage levels required by
the system.
3. These voltage levels typically are monitored by one of the Sony sound integrated
circuits on the logic board. If the levels are acceptable, a reset signal
is then generated by this IC.
4. This reset signal forces the central processing unit (CPU), math coprocessor
(FPU), primary logic ICs, expansion cards, and other internal devices
to come to a known state.
5. The reset signal is withdrawn.
6. The CPU obtains the reset vector (typically four eight-bit words), which
begins at memory address 0000 0000 (hexadecimal). A ROM overlay
address map then is used by the memory decode and control circuitry to
map the standard memory locations to a ROM address. The CPU goes to
the reset vector memory address, which is now mapped to ROM.
7. Special program code called the Macintosh reset handler (MRH) is executed.
The MRH remaps ROM and RAM to their respective locations.
8. The MRH initiates the P.O.S. T. sequence."

Is it the sound chips thats not working? Defect RAM? The soundchips UB7 and UB8 is closest to the caps C9-C11 .





I´m greatful for any advice.

 

[reallyrandy]

I have an si that will not boot with no RAM. I just thought that was standard.

 

[techknight]

Even if the on-board RAM was bad, you would still get slow chimes of death. 

 

[techknight]

One more thing. Did you wash the board after the caps? That is important!

 

[BEU]

One more thing. Did you wash the board after the caps? That is important!

Yes, I cleaned the board with isopropylalcohol after removing the caps. Cleaned with q-tips with aceton were the caps had been. I have recapped SE/30 boards before and I think this one looked rather good. No battery leaking. No obvious destruction on the traces. But I realize that one should look for defects around the caps. All the fuses on the board are tested and are OK.

A picture of the board before recapping..

 

[techknight]

no no, I mean WASH the board. physically like in a dish washer, or an ultrasonic cleaner? The shit gets under the ICs and sometimes vias themselves and causes issues. 

 

[sigtau]

I have a IIci that does this, and I narrowed it down to believe that it's a result of bad caps/broken traces on the logic board that emanate out from the power supply connector.  Haven't had a chance to fix it as I just finished moving.

That said, here's what I know: The symptoms disappeared when I completely removed the caps in that vicinity, but not other caps; but, of course, it wouldn't boot with them removed either.  I think it's a trace coming from the 12V rail, because mine starts from the ADB power button (which requires 5V), but gets no further.

Visually inspect the whole board and dishwash it with hot water and no detergent perhaps?

 

[BEU]

no no, I mean WASH the board. physically like in a dish washer, or an ultrasonic cleaner? The shit gets under the ICs and sometimes vias themselves and causes issues. 

Visually inspect the whole board and dishwash it with hot water and no detergent perhaps?

Thank You techknight and sigtau for Your comments. I will try to find a ultrasonic cleaner for a reasonable price. If not it will be the dishwasher..

 

[techknight]

We got an ultrasonic cleaner at work, and its by far the best thing that I have come across. A heavily crappy flux-filled, corroded, etc PCB comes out looking brand new. 

We use it after wave soldering and SMD machine assembly/reflow, then I go back and solder on the non-wave-able components and run it through the cleaner. 

 

[BEU]

A heavily crappy flux-filled, corroded, etc PCB comes out looking brand new. 

I have used an ultrasonic cleaner that I found on ebay, made in China. Its working fine. During cleaning it was like smoke coming up from the MB under the  RAM chips. Cleaned with distilled water mixed with cleaning fluid. The MB looks like new but unfortunately the MB is not working. Same result as before cleaning.

I will desolder and clean UB7 and UB8 , maybe that can help. Otherwise I dont know what to do.

 

[bibilit]

Hi,

I have got two of those, both with the onboard Rom, and the two have the jumper W1 removed (disabled) 

I have tested one of mines last week (recaped the board and PSU) so pretty sure works this way, maybe yours is looking for the Rom simm, unable to find it and would not boot ?

 

[BEU]

I have got two of those, both with the onboard Rom, and the two have the jumper W1 removed (disabled) 

I have tested one of mines last week (recaped the board and PSU) so pretty sure works this way, maybe yours is looking for the Rom simm, unable to find it and would not boot ?

Hi bibilit. That’s a little confusing for me.

For Mac II-series machines with ROM SIMM slots, check to make sure the W1 jumper is removed (if a ROM SIMM is installed) or installed (if the ROM SIMM slot is empty).

http://www.ccadams.org/se/pickle-faq.html

According to BMOW , Mac IIsi: Insert a jumper at location W1 on the logic board if a ROM SIMM is installed.

https://www.bigmessowires.com/romdrv/rominatorii-instructions.pdf

When I got it it was no jumper, no ROM SIMM, no RAM SIMM, (not working).

I have tested my MacIIsi board ( 820-0301-A, 630-0265) with and without jumper and w/wo a working ROM SIMM from SE/30.

This rom SIMM with number 820-0241-02 has been reported to work in the Iisi before.

https://68kmla.org/forums/index.php?/topic/127-iisi-rom-simm-part-number/?hl=820-0241&do=findComment&comment=80676

ROM SIMM      W1 jumper   Result

0                       0                  Black screen , no sound, not booting

0                       installed      White screen, no sound, not booting

SE/30               0                 White screen, no sound, not booting

SE/30               installed      White screen, no sound, not booting

Is that indication that the ROM is not the problem???

 

[bibilit]

The IIsi will work without the jumper if no Rom simm is present, so BMOW is right.

So probably your problem is not in the ROM side.

 

[corbinq27]

I’ve got a IIsi that I recapped, cleaned and seems to have the same symptoms as yours. Did you happen to have any luck with this one?

 

[JC8080]

I’ve got a IIsi that I recapped, cleaned and seems to have the same symptoms as yours. Did you happen to have any luck with this one?

I'm in the middle of a repair on mine, it's on the back burner at the moment, but one thing I found was loose pins on ICs around the leaky caps. Very gently take a dental pick and push on the legs of any ICs near the leaking caps that show any corrosion. I found multiple pins, including on the CPU, that looked fine but moved when I pressed on them since the solder had been eaten away by the cap goo.