Black screen breadbin 64

Aysel

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Hello all, no video output at all :-(

Nothing from rf or chroma video connector to a 1084s, it just gives a black screen. Through rf it goes from white noise to black screen when turned on. I have tested psu and its giving a steady 5v. There's still power running through to the tape deck as it still plays.

Is there anything I can try to narrow the fault down?

Thanks in advance :)
 
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I will say from experience that the PLA chip is dead. By far the most common component to fail.
 
Morning ..... I am sorry to say that the black screen of death is quite common on C64's ........ As you have already checked the voltages on the psu, it could be one of many things that could go wrong. Please refer to this link to get you started http://personalpages.tds.net/~rcarlsen/cbm/c64/c64-ic.txt . In my experience I have never had a PLA fail on me once, but that is not to say it does not happen. If you feel confident open the case and start the 64 and check the heat generated by the chips. Check the PLA first if it is red hot (It should run no hotter than the SID) then you might of found the culprit. Also check the ram chips to see if they are running very hot.

Also different revisions of the motherboard had certain chips socketed and some soldered. You should check that all socketed chips are firmly in place and clean the sockets with IPA.

I hope these tips help :)
 
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a diagnostic cartridge only works if the machine still boots...

also a black screen can be caused by about 20 different ic's in c64 depending on revision board

my first port of call would be the 12 and 5 volt regulators inside the c64 if they are not outputting the voltages the screen will be blank as the machine needs those rails to supply the vic in the breadbin model.
and the on/off switch,can fail and the rectifier,so check all the power rails before and after the switch.
and check the fuse is ok,dead fuse in the breadbin equals no video.
easy test with a meter would confirm they are ok.



i can take a look at the c64 if you send it to me to test the individual ic's if a basic test reveals nothing.shipping wont be that bad via courier.
 
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Thank you all for the comprehensive replies... really helpful advice :)

Roy will drop you a quick PM.
 
check the output of the voltage regulator inside the breadbin, 7805 for 5V and 7812 for 12V (look for "7800 datasheet" on google for pin diagram).
check pin 21 and 22 of VIC, voltmeter have to read 1.5---2V (middle logical point between 0 and 1) otherwise the clock generator 8701 is damaged.
A cartridge called "dead test" can boot the C64 with (some) failure in RAM, ROM, CIAS but have to work the 6510,pla,the bus loads and some logical chips.....
 
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c64 is now repaired,ive sent a pm for return address details etc.

just got to test it some more to be sure and pack it up for the return journey.

lets see if anyone can guess what it was...

attachment.php




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A blob of solder broke and insulated a diode? Serious?
 
Then the problem is the most common failure: a toasted RAM chip.
 
I inspected the photo (is a bit blurred on my monitor) and the only thing I think I saw was that diode over the resistor that appears to be snapped of. So I quit guessing. :)

What was wrong?
 
I inspected the photo (is a bit blurred on my monitor) and the only thing I think I saw was that diode over the resistor that appears to be snapped of. So I quit guessing. :)

What was wrong?


ok bud,it had no reset on power on.so it was a failed 556.

it took 5 minutes to diagnose but i only juist got round to fixing the problem.
 
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Cant wait to get it back :D

The machine lost video whilst working my way through a load of old disks from my teenage years... its was litteraly minutes after firing up Sam Fox Strip Poker so Im 99% sure Sams magnificent magenta baps pushed it over the edge :D

Thanks for your efforts Roy, and the updates throughout.. greatly appreciated!
 
P5225589.jpg

Board arrived safe and sound this afternoon.... working perfectly. Cant thank you enough Roy, absolutely top job all round!

Best regards, Mat
 
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