LC475 with no video

[falen6]

Hi all

recently got me an LC475

battery did not leak

caps did

removed old caps and solder - scrubbed board - recapped with tants

power on gives good chime but no video display

have tried different vram pairs , tested on another machine

have tried different ram sims , also known to be good

still no video

when i add a ram simm i get bad chime , so thinking ram problem

then i pressed on first onboard ram chip next to c128 and c127 and hit the power , i get very fast chimes of death

i dont press on anything and i get good startup chime

c127 and c128 ( along with all the other caps ) leaked all over the place

the board has been thoroughly cleaned over and over with iso , acetone , ..... even boiling water !! - still no video

also - when i add ram expansion i always get chimes of death

so im thinking it is the onboard ram , bad pin / pad / trace connectivity

I have already reflowed all the onboard ram chip pins , still no video

If I have an onboard ram problem how come I am getting a good chime

also - even thought i have no video output I think the computer is crashing after the good chime as it will not boot from floppy or reboot when doing the command, option , p , r reset - nothing

i DONT have a pram battery installed ( have to get one ) but even the quick off and back on trick yields no video

im thinking of using hot air to take off the ram chips next to c127/128

just wondering if anyone has had similar issue

cheers

 

[Realitystorm]

I never had any luck with the quick on and off, I only get video with the pram battery installed

 

[falen6]

I never had any luck with the quick on and off, I only get video with the pram battery installed

thanks storm

i have a 3 volt dc power adapter - u rekon it would be ok to wire that into the battery holder terminals just to see ? , just to test it

i really dont want to blow this up !!!!

 

[falen6]

also - i have tested the power , even swapped out the psu from my working lcIII , thats where i swapped the simms just to see

they all come up good

 

[shirsch]

From my experience a battery is required in order to get video display.

 

[croissantking]

I’ve had good results with quick on and off.

 

[falen6]

ive ordered up a few of those 'macbatt' things

i had a 475 before and the quick on/off/on always worked for me as well

who knows

maybe its part of the startup sequence , that if the video is not initilized the start up freezes

 

[Juror22]

From my experience a battery is required in order to get video display.

Ditto on the battery with this model. And I have much better luck since I started using a white vinegar soak to eliminate the cap juice (followed by DI water and 99% alcohol) for what its worth.