Re: C128 boot problem - please help.

I've experienced the same problem myself. Ultimate fix is to change the power switch, but it could be just a bad solder joint on the switch it's self. You *could* have micro-fractures on the board as well, but those can be really painful to locate... I hope it is just a bummed switch.

Marcop wrote:
Ray Carlsen <rr0cc@xxxxxxxxx> wrote in
news:fbmgke$o7s$1@xxxxxxxxxxxxxxxxxxxxxxx:

Thank you to everyone who has replied. I verified the PS voltages with the C128 powered on. Both when it functions and when it doesn't, the voltages are in spec. I even checked the output of the 12V regulator and it is fine too.

I am running the 128 in 40 column mode with only the 1571 drive and 1902A monitor attached. No other peripherals are hooked up. I can continuously toggle the on/off switch and every once in a while the C128 boots fine. Once I pressed the reset button and it booted fine too. I have wiggled the power supply cord (near inlet of C128) after it boots correctly and it doesn't seem to crash the computer. What I have discovered is that gentle taps on the center of PCB seems to crash (after a good boot) the computer rather easily. At first I thought that perhaps the bottom of the PCB was touching some part of the metal plate underneath the board so I removed it from the enclosure (and metal plate). Again, gentle taps to various parts of the PCB would crash (garbage on screen or lockup after good boot) the computer. It seems most sensitive towards the middle of the PCB.

To reset the crash I power cycle with the main switch. Occasionally it boots well immediately. After several unsuccessful boots I apply a little pressure to the PCB (by gently bending by a couple degrees on the ends of the PCB) and it tends to boot immediately afterward.

Conclusion... probably a broken solder connection on an IC pin or a broken trace due to abuse of 128 by previous owner. Could have been caused by bending of enclosure by placing something heavy on C128 or packaged unit while one of of C128/package resting on something. What do you think? This is going to be a pain to find.

Thanks again for the help.
Marco


Could someone help me out? I was recently given a C128 that has a
strange boot problem. 9/10 times the 128 failes to boot. The screen
either either a solid color (black, purple, others?). Sometimes
there is garbage characters flickering on the screen. When I first
turn the computer on the 1571 drive light comes on as normal but it
doesn't go into it's seek mode afterwards. If I press the reset
button then the 1571 drive's red LED light's up for a split second
then goes out. On the few times that it does boot the system
behaves normally. I have run some programs on it. Occasionally when
the system is running it will crash. However, I have run it for
about 5 minutes (C128 demo) without crashing. I sometimes move the
unit around and the problem comes and goes which may indicate a loose
connection or cold/broken solder joint. However it is very hard to
pin down if this is actually what is going on because it is not
repeatable. I have tried the following:
- reseat all socketed IC's.
- resoldered PS connector on motherboard.
- checked fuses and voltage levels on PS (5.2VDC and 10.2 AC).
Marco,
See if the paddle of the power switch is binding on the C128
case. I've seen a few of them that would not allow the switch to fully engage. If
it is binding, you can trim the plastic around the switch to free it
up. If that's not the problem, try switching the computer on and
-then- connecting the PS to the AC outlet. If that works reliably, the
switch may be intermittant inside and if so, should be replaced. Next,
wiggle the power connector while the computer is running to check for
glitches. The power socket itself may be intermittant. The pins inside
the socket eventually get loose and don't make good contact. They can
be tightened with a straight pin by gently prying each side inward a
bit, if that's the problem. Mechanical intermittants can be really
frustrating but usually point to bad connections as you indicated. Flexing and tapping on the board around suspected problem areas is the
best way to make such intermittants show up. Good hunting!

Ray

.

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