bbadger@x102c.harris-atd.com (Badger BA 64810) (03/09/89)
I have a couple of C64's with a similar problem: when powered up, the display is blank and the keyboard seems to be locked up. By flicking the power off and on, I can sometimes get ``garbage'' to come up on the screen, so this proves that the video is basically sound (i.e., VIC, xtal, etc.). You can probably get your machine into a similar state by unplugging the keyboard from the main board. The screen remains blank. I had this sort of problem twice before, and replacing the keyboard 6526 (Peripheral Interface Chip) did the trick. The first time this happenend, I remember swapping the two 6526's and getting either a keyboard that worked, or a disk drive that worked. Anyway, I bought a new 6526, and that didn't fix it. I have a total of 5 chips available and tried all 20 (5*4) combinations in the two spots with no luck. (Of course, the chips themselves are suspect, since 4 of them came from the two "broken" machines.) Does anyone familiar with C64 kernel boot-up ROM code know if my suspicions about the keyboard interface are reasonable? That is, if the kbd PIC is bad, a black screen is displayed because the ROM code will not proceed to the point where the VIC is properly enabled. Don't sweat too long on this one --- I'll probably just buy a new C64 anyway. Bernard A. Badger Jr. 407/984-6385 |``Use the Source, Luke!'' Secure Computer Products |``Get a LIFE!'' -- J.H. Conway Harris GISD, Melbourne, FL 32902 |Buddy, can you paradigm? Internet: bbadger%x102c@trantor.harris-atd.com|'s/./&&/' Tom sed expansively.
jgreco@csd4.milw.wisc.edu (Joe Greco) (03/09/89)
In comp.sys.cbm article <1661@trantor.harris-atd.com>, bbadger@x102c.harris-atd.com (Badger BA 64810) wrote: ]I have a couple of C64's with a similar problem: when powered up, the display ]is blank and the keyboard seems to be locked up. By flicking the power off ]and on, I can sometimes get ``garbage'' to come up on the screen, so this ]proves that the video is basically sound (i.e., VIC, xtal, etc.). ] ]You can probably get your machine into a similar state by unplugging the ]keyboard from the main board. The screen remains blank. I had this sort ]of problem twice before, and replacing the keyboard 6526 (Peripheral ]Interface Chip) did the trick. The first time this happenend, I remember ]swapping the two 6526's and getting either a keyboard that worked, or a ]disk drive that worked. ] ]Anyway, I bought a new 6526, and that didn't fix it. I have a total of 5 ]chips available and tried all 20 (5*4) combinations in the two spots with ]no luck. (Of course, the chips themselves are suspect, since 4 of them came ]from the two "broken" machines.) ] ]Does anyone familiar with C64 kernel boot-up ROM code know if my suspicions ]about the keyboard interface are reasonable? That is, if the kbd PIC is bad, ]a black screen is displayed because the ROM code will not proceed to the ]point where the VIC is properly enabled. ] ]Don't sweat too long on this one --- I'll probably just buy a new C64 anyway. ]Bernard A. Badger Jr. 407/984-6385 |``Use the Source, Luke!'' ]Secure Computer Products |``Get a LIFE!'' -- J.H. Conway ]Harris GISD, Melbourne, FL 32902 |Buddy, can you paradigm? ]Internet: bbadger%x102c@trantor.harris-atd.com|'s/./&&/' Tom sed expansively. I doubt it. Several of my C64's run keyboard-less quite a bit of the time. Electronically, there is no way for the 64 to know if the keyboard is connected. It sounds to me like a brain dead (hehe) 64. Probably a blown 6510. Failing that, a PLA chip. It's not too easy to tell when problems are more complex than that. Bad RAM, bad logic, all cause similar symptoms. With that many spare parts, you shouldn't have problems finding the bad chip. BTW, sometimes 40 pin sockets are "loose." Wiggling a chip a little sometimes cures mystery problems. -- jgreco@csd4.milw.wisc.edu Joe Greco at FidoNet 1:154/200 USnail: 9905 W Montana Ave PunterNet Node 30 or 31 West Allis, WI 53227-3329 "These aren't anybody's opinions." Voice: 414/321-6184 Data: 414/321-9287 (Happy Hacker's BBS)
asmodeus@tree.UUCP (Jonathan Ballard) (03/12/89)
In article <1482@csd4.milw.wisc.edu>, jgreco@csd4.milw.wisc.edu (Joe Greco) writes: > In comp.sys.cbm article <1661@trantor.harris-atd.com>, bbadger@x102c.harris-atd.com (Badger BA 64810) wrote: [....] > > It sounds to me like a brain dead (hehe) 64. Probably a blown 6510. > Failing that, a PLA chip. It's not too easy to tell when problems are > more complex than that. Bad RAM, bad logic, all cause similar symptoms. > > With that many spare parts, you shouldn't have problems finding the > bad chip. > > BTW, sometimes 40 pin sockets are "loose." Wiggling a chip a little > sometimes cures mystery problems. This is not always true. Commodore power supplies go out often in this is one syptom. I found most of my problem related to a partial dead power supply that is about to go all the way out. The power supply will make it look like the chip are going out because it doesn't always give full power when they are going out. So those 20 chips may all be working just fine! And so all the other C= computer you have. I've heard that third party power supplies are better then Commodores. Sometime they cost more sometimes they're less. Usually they are always not as hot! -- ----Asmodeus - Jonathan Ballard ..!csusac!tree!asmodeus ..!pacbell!sactoh0!tree!asmodeus "I'm going to create the best game ever heard of! Might take a few years thou..." -me