c64 back from the dead.

[mjnurney]

I've had a dead c64 motherboard kicking around for a year or so now and it never worked , always a black screen.well tonight i thought i better solder back in some missing chips and test it properly as my old project c64 is starting to play up...

anyway.the good:voltages all ok sid goodvic good kernal rom good (my jiffy dos)the bad:black screen.CIA 1 (left) heats up to scolding hot - DEAD.

but before i can test this properly , i have to find / replace the missing : U6 2114 ram , U27 - 74ls08n (logic gate) & 74ls373N (decoder latch)

Sooo with these found / replaced with new ones its time to power on and still a black screen as before but the CIA is still getting red hot so we will have that out and try again - still dead.okay so lets work from socket to socket as each large chip is socketed on this c64 - and bingo - its the kernel (u4 ROM) if i pop my jiffy dos rom in the c64 boots to nonsense or if i pop a cartridge in it will boot up.So , i need to find a 6526 CIA chip and a kernel Rom...all good fun , mike.

will burn a dead cart tomorrow and do a ram test / diagnostics...as i have no keyboard access with a dead CIA at the moment.
**I've fitted 2x Amiga 2000 / 500 cia chips and i now have keyboard access and it boots carts properly but i have no basic at all - so i suspect the basic rom is dead too.

** dead test shows the following.

BAD PLA
BAD BASIC ROM
U1
U2
U18
U17

but apart from that , all good

 

[roy_bates]

youve got to love the near never ending diagnostic on these mike...well,ok.not really.(the love bit)

but they are satisfying to fix.

 

[mjnurney]

i like the c64 but the faults are very much like cars ....fix one and another is waiting

they don't put c64 in cars do they?

in truth i had a suspicion about most of the chips on this board , it was a bitsa motherboard with all the good stuff taken off and all the junk plugged back in.

 

[roy_bates]

i had one like that mike,were someone had used it as a donor and put all the bad bits on the board....


why? for the love of god do people do that? just bin the bad parts,what good are they.

jokes aside,i dont hink it would make it any more interesting to fix...or would it.

 

[mjnurney]

not sure why you would keep bad chips - i don't , i'll only mix them up with good ones and spend hours wondering why it doesn't work

on the hunt for 2x cia , pla , kernel and basic rom ..........ahhh all the machine almost

 

[roy_bates]

well,ive definitely got the kernal and basic rom if you want them just shoot me pm,i may have cia's but dont put your hopes up on those mate.

i do have a spare pla,but thats a spare for mine mike sorry...but you could make one from a eprom.

 

[mjnurney]

thanks roy , basic and kernel are most important to get her running , the amiga CIA;s can stay in. as for the PLA i can burn one of those

i wonder if i can play with the kernel and have an eprom with different OS on it...

 

[roy_bates]

just shoot a pm and i'll drop them in the post...

well,you know you could just make a dual boot system.its easy enough mate.

 

[mjnurney]

mmmm ideas.

your a gent Roy

i wonder what hacks have been done ....cpu speed / ram / colours .... better have a look

 

[roy_bates]

im not sure about cpu speed mike,as its all tied together at the vic.

ram,dunno.always wondered about that.

colours?

 

[mjnurney]

I'm sure dave haynie said they had a water cooled VIC running at 8mhz in 1983.... although i may of made that up

ram and REU i suppose and whats the point...

colours sure I've seen a c64 with some (many) colours ...google search i think

 

[Paradroid90]

Great Work Mike.....Good to see that another 64 is being brought back to life

 

[mjnurney]

thanks bud , the hours these things consume !!

 

[mjnurney]

I've decided to pop it in a case and try an LCD screen on the old girl too

B/W at the moment thru composite.

(pal)

EDIT..

colour now: Small video screens suit the c64 , although this one maybe a little too small

this most of been the post i saw about colours:
http://www.studiostyle.sk/dmagic/gallery/gfxmodes.htm

youtube vid too.

https://www.youtube.com/watch?v=PXnKvYUeUm4&feature=youtu.be

very little sound as i have no amplifier yet..

 

[johnim]

nice work as always mike

 

[protek]

Awesome work, Mike!
I have a similar display. It's pretty handy when you're testing stuff. Mine just doesn't like to sync with all of my gear.

 

[mjnurney]

thanks guys

Kernal rom and Basic rom arrived from Roy, cheers bud and now the prompt appears and the machine seems to work fine now for the first time since I've had it

now i just have to find the metal plate that fits behind the joy ports - i know i have it

 

[roy_bates]

awesome.

 

[Paradroid90]

Cracking Mike If you cannot find that plate I might have one kicking about you can have free of charge

 

[mjnurney]

thanks bud , i know i have one .....i picked it up about a week ago...