Another strange problem
My II europlus crashes 1 or 2 minutes after I power it up.
If I keep at it (switching it on and off, reseating chips) it ends up not coming on at all, just a screen of random characters , as if there is a ram problem.
Spent a few hours last night and gave up. Just could not get it to boot at all
Today I switched it on and it boots fine, but again after a few minutes it starts to crash
I have recapped the power supply and tried several similar power supplys to be sure it is not the PSU.
Is this a capacitor problem - namely the 2 caps up by the power connector?
Dang! - these old machines are TEMPERAMENTAL
Hello falen5,
you should waste more time thinking about that "timeframe" of 1 to 2 minutes....
this usually indicates a problem with temperature.... in some cases i have faced
similar problems with spikes on the powerrails...
It's a known problem, that the filtering of spikes at the mainmboard is rather poor
( that 100nF ceramic caps added between the rows of the RAM chips... )
If you have chance to get oszilloscope i'd view the power close at the RAM-chips
at all 4 powerlines ( +5Volt, +12 Volt and -5V ) hunting for spikes and noise...
in case that noise causes the trouble replacing that ceramic caps solves the problem...
bad aged solder joints can be source of the trouble or caps bent in the one or
other direction...
hint : keep for a while the harddisk disconnected... and examine if the
causes change in that "timeframe" and hunt for chips that heat up in that timeframe
sincerely
speedyG
will do speedy - thanks
replaces the 2 10uf caps at the power connecter
still the same
reflowed all the ceramic caps
still the same
no shorts on the power rails to ground
it has to be left unplugged for 20 minutes, then it boots up. lasts 1 minute, crashes - then the roms and the ram start heating up fast
does not make sense at all
i have spent ages watching the voltages coming fropm the power connector on the board - 4.9 , 12.2, -11.7
they seem fine
im using a typical digital multi meter - if there were voltage 'fast' spikes , could the multi meter 'possibly' not show them?
i need to learn how to use this dam scope - I have a Tektronics TDS3054 behind me on a shelf - have never used an osiliscope in my life
Ok sounds to me like the power rails are good. I would say you have a specific chip that overheats and fails, not necessarily
a chip that feels warm. Since it's a plus, you could pull all the ram except one row nearest the keyboard connector just to eliminate some chips.
Find a function that works when cold but not when warm so you can repeat the test then put an ice cube in a ziplock bag to seal the moisture
and start putting it on a chip by chip to see if that function is restored. It should start working almost immediately after cold is applied to the bad chip.
Larry G
Im not having any luck with these old boards.
I have 3 of these II plus boards - and none of them work
This one - i have remove all but the first row of ram. Have reseated/swapped every chip, over and over
Discovered that as you carefully remove chips the last 2 pins to leave the socked may bend a little. By straightening these pins again seems to have improved things.
But everything is inconsistant- Each time i power up the board I get different results, patterns on the screen, beep, sometimes no beep, sometimes a high pitch beep, sometimes 2 beeps, then sometimes it boots up - all this without changing anything - is this normal?
For the other 2 boards I get a beep (sometimes) , but the screen is a mess (random junk) - although I have only 1 working character rom
I am starting to thing my recapping of the power supplies may be flawed. The caps I used are radial, same value, correct polarity, but about 1 third the size of the old caps. From what i have read that is normal when replacing old caps ( the new ones are always smaller)
Why is there such inconsistancy when i power these boards up? - the on/off switch 'grinds' as i operate it. Could this be causing a spike in voltage of some kind?. I tried powering up the board using the power connector to the board but I think this will cause 'spikes' as well
I have 2 power supplys from ii plus's and power supplys from IIe's. My IIe machines boot fine on them. Is there any subtle differences between the power supplys of a iie and a ii plus in terms of voltage?
Will try freezing the board later - good idea - see what results is gets
Have been at these boards since december and still no joy
when a board gives out a good beep at startup does that mean allot of things are working?
paitence is a virture
If RAMchips are not correct in socket
it's normal that this chips get killed by the supply voltage !
That's the reason that after reseating every chip must be
checked twice for correct insertion and bent legs.
have spent weeks at these speedy -
I make sure the chips are in correctly
When i say bent pins - i mean slightly bent off perpendicular
tell me this - if the board emits a beep and fails to boot how much of the system is actually working?
would the beep indicate good ram, cpu, and the majority of the board ?
have discovered i can get a beep with all roms removed except F8 - so this makes me more confused
what does the beep mean in terms of functionality
somewhere between E8 and F0 ROM code...
do i remember correct that you are located in Ireland ?
reply as pm...
a II+ motherboard alone requires twice the power of a //e
thanks for that retrogear
Thats an important thing to know
Im starting to think my woes are ALL power supply problems