Decoupling capacitors

[orange]

Are they really needed? I've checked EVERY bloody trace to every DRAM chip on {bleep}ty a501 with batt leakage. Also replaced 3 capacitors and checked resistors. But there are some 16(!) decoupling tantal capacitors that arent checked/replaced. they are expensive to replace and I don't know capacitance, anyway. So I thought about simply disconnecting them if they are not necessary?  :roll:

[orange]

What kind of 'examination'? Capacitors look fine.
Could I use cheap alum ones instead of tantal?
What table? from where? I got several schematics. Besides, value of other capacitors and resistors are DIFFERENT from those written on schematics. There are some small numbers printed on capacitors, but they seem to be different for each one  :-? and its not something understandable like '10uF'
hmm, I probably should try measuring their capacitance..
How do I know which one is blown?

[orange]

Here it is, finally:
http://qrange.150m.com/pictures/a501.htm    (900Kb!)

[orange]

A500 works with other slow_fast 512K RAM expansions. I got A501 broken. Actually it did work only once before I disassembled it to remove dead batt. BTW, could it be that metal case is required for operation?  :-?

[orange]

none of capcitors are short.
A500 runs but always with fast = 0Kb, strangely CLOCK works! I  checked everything except chips (and dont know how to check them)

Someone said once that chips can be tested if they are on for 10 min or so and then checked if they are warm or not, could that be the answer? :-?

[orange]

arrrr... ALL TRACES ARE GOOD!!!
The voltage is a bit lower, about 4.78 V..

[orange]

I've measured again, its 4,84 V on all chips. They don't get hot but I don't know for how long A500 should be on.

BTW, if just one of them is faulty none works?