Help needed to fix my C64 - rare KU-14194HB

Got an issue?
vgfl
Member
Member
Posts: 3
Joined: Mon Mar 01, 2021 4:15 am
Contact:

Help needed to fix my C64 - rare KU-14194HB

Post by vgfl »

Hello there,
I am hoping that somebody will find the reason why my C64 displays a black screen. I checked all voltages, they seem all okay (I have three power supplies, black screen with all of them).

I have a thermal camera, so I attach a snapshot of the motherboard. For some reason the coloring is shifted by approx. 1 IC width towards the top. As expected (roughly from top to bottom):

- The two voltage regulators are warm.
- The VIC-II chip is warm too.
- The audio IC (the hottest at 48.4C), the processor, the PLA are all warm.
- One memory chip has a hot spot.

I have two VIC-II chips on order to see if they change something.
I also have the PLAnkton EV ordered from eslapion (this one will be a challenge to install, as the PLA and Processor are so close, it is impossible to insert an IC removal tool).

Thanks!!!
Vincent
Attachments
20210302-090332.jpeg
20210302-090332.jpeg (119.74 KiB) Viewed 1569 times


User avatar
eslapion
Active Member
Active Member
Posts: 1019
Joined: Mon Jul 20, 2015 10:11 am
Location: Canada
Contact:

Re: Help needed to fix my C64 - rare KU-14194HB

Post by eslapion »

vgfl wrote: Mon Mar 01, 2021 4:25 am - One memory chip has a hot spot.
The prime candidate...
I also have the PLAnkton EV ordered from eslapion (this one will be a challenge to install, as the PLA and Processor are so close, it is impossible to insert an IC removal tool).
I suspect you'll have to consider a Saruman-64 for the faulty DRAM.

Removing the PLA is easy with a small flat screwdriver. Lift each end a little bit at a time and you'll get there.

Very nice to have thermal imaging. Quite impressive.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders
vgfl
Member
Member
Posts: 3
Joined: Mon Mar 01, 2021 4:15 am
Contact:

Re: Help needed to fix my C64 - rare KU-14194HB

Post by vgfl »

Thank you, eslapion!
vgfl
Member
Member
Posts: 3
Joined: Mon Mar 01, 2021 4:15 am
Contact:

Re: Help needed to fix my C64 - rare KU-14194HB

Post by vgfl »

Actually, I was mistaken, it's not a memory chip at the bottom, it is the Hex inverter, the HD7406P, so I guess it is normal that it is warm. It has the right voltages.
I'll wait for the PLA and for the VIC-II chips to see if it changes anything.
Vincent
User avatar
eslapion
Active Member
Active Member
Posts: 1019
Joined: Mon Jul 20, 2015 10:11 am
Location: Canada
Contact:

Re: Help needed to fix my C64 - rare KU-14194HB

Post by eslapion »

vgfl wrote: Mon Mar 01, 2021 5:09 am Actually, I was mistaken, it's not a memory chip at the bottom, it is the Hex inverter, the HD7406P, so I guess it is normal that it is warm. It has the right voltages.
Considering where it is relative to the CIA, I am quite sure the hot chip is U9 and it is a DRAM IC.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders
Post Reply Previous topicNext topic

Who is online

Users browsing this forum: Google [Bot] and 2 guests