latest updates and corrections 1-31-2020

THE LUMAFIX, INSTALLATION AND SETUP

     This module is a plug-in device that goes between a C64 VIC chip
and its socket... unplug the VIC chip (it's always socketed) and plug
the module into the motherboard, then plug the VIC chip into the
module. Note the orientation of the board and IC with the notches on 
one end. With three on-board controls, the user can reduce or in most 
cases eliminate the vertical lines when the computer is used with a 
high resolution monitor, such as the S-video input of an older TV. 
These lines are almost invisible when viewing an original Commodore 
monitor such as a 1702 or 1084 so Lumafix may not be needed. 
     There are a few things not mentioned in the original instructions
for the Lumafix module. First and most important is that the original
heat sink for the VIC chip must be removed to install the module but
nothing is said about how to replace it. The chip and module sits up
much higher and the original heat sinks cannot be put back. In all 
but the latest version (true C, short board 250469) of the C64, the 
VIC chip will overheat and eventually burn out without a heat sink! 
Some means of replacing the original must be found to keep that chip 
from overheating when the Lumafix is used. Even if the original VIC
socket is removed and the Lumafix is soldered directly, it still sits
up too high for the original heat sink to be put back. 
     The two early boards (326298 and 250407) have a metal cover over
the VIC area and that cover has an internal metal tab that presses
against the VIC chip to draw away its waste heat. Several other chips
run very hot normally and fail more frequently because they have no 
heat sinks. Later boards (250425 and 250466) have a factory metal 
shield with half a dozen tabs for all the chips that need cooling 
including the VIC. Note: there are two versions of that metal shield.
Depending on which shield you have, there are different ways for 
implementing a VIC heat sink. See photos.
     Note the latest version C64C (250469) uses a different "family" 
of chips (85xx series) and those IC's don't need heat sinks. The shield 
can be removed and safely left off that board or the area around the 
VIC can be cut out of the shield to allow space for the Lumafix module. 
     One other point that should be made is about how the Lumafix must 
be adjusted to clear the screen of vertical lines. When the module is 
first installed the screen appears much worse than without it. Because
of this, some have assumed the module must be bad... but it's normal. 
To adjust the three multi-turn pots for a clear picture they must be 
turned many times with a jewelers screwdriver. They have no mechanical 
stops to indicate end of travel unlike standard controls, and it's
difficult... the screwdriver slips out of the slots repeatedly. Turn
many times one way and if no correction is seen, start turning the
other way until the distortion is minimized with that control. 
     I always start with the center control, minimze the picture lines,
then go to the far end pot and continue, back and forth until the 
image is clear. The third control is for color adjustment. You may not
see any problem unless you're using an S-video cable into a high res
TV or monitor. Then the color distortion (checkered pattern) error 
appears and adjusting the color level control should correct it. 

LUMAFIX AND HEAT SINKS

First, some basics... Semiconductors (diodes, transistors, IC's) all
generate some heat in normal operation. Large complex IC's like the
VIC and MPU will get hot. It's not just the heat that destroys them 
but the thermal cycling of heating and cooling that does it. To keep
the extremes of heat under control, waste heat is transfered to the
heat sink and into the surrounding air. Since there is little air 
flow inside a closed c64 case, it's important that the heat sinks are 
adequate... bigger is better to reduce "hot spots". The best way to
tell if a heat sink is working: run the computer for 5 minutes with 
the case closed but case screws removed, then power down and quickly 
open it and feel the center of the IC or sink. It should NOT be hot 
but just warm if the sink is doing its job. 
     There are several basic versions of C64 boards. As mentioned, the 
two early boards usually have a tinfoil/cardboard shield. That "shield" 
is good at holding -in- waste heat and not very good at blocking RF 
interference from the computer. It's best to just remove and discard 
it. When the metal VIC cover is removed to install the Lumafix, some
means must be found to replace the VIC heat sink. Without one, in all 
but the latest board, that IC will get hot enough to burn you after 
5 minutes running time. For a replacement heat sink in those boards, 
I propose a metal strip bent into a U shape fitted over the IC and 
contacting the base metal in the VIC area. That draws waste heat away 
and into the surrounding metal. That metal strip can be fastened to 
the metal base with epoxy or some other glue so it can't fall off and 
short something out if the computer is moved. The first one I ever
installed was soldered to the base metal but that makes it more 
difficult to remove the VIC if replacement was needed. Aluminum is 
easier to work with but can't be soldered and so must be anchored with 
some type of adhesive such as epoxy. If you use strips of tin or steel, 
they can be soldered to the shield or the ground foil of the board. 
     The later version C64 boards with their metal shield must either
have that shield modified or a portion of it cut out to install the new
module. Regardless, a heat sink must be used for the VIC. If the 
shield is not put back, individual heat sinks must be attached to the 
VIC and other chips that run hot normally: the SID, PLA, MPU and Kernal 
ROM. Notice those chips are frequent failure items.
     I don't like the peel-and-stick adhesives as they don't transfer 
heat very well. I usually use fast set epoxy (JB KwikWeld) to attach
heat sinks. Once set it's very difficult to remove so if an IC goes 
bad, the sink goes with it. I make my owns sinks... no great loss.
     The most difficult computers to work with are the white case C64C
versions long boards. This is because of the low profile of the white 
case. That keyboard sits lower, closer to the motherboard, making 
installation of a proper heat sink for the Lumafix VIC more difficult. 
Any sink on that assembly will have little airflow around it, so a sink 
that contacts the original shield is best. As mentioned before, the 
250469 C64C short board doesn't really need heat sinks on its chips but
I'm a perfectionist, so I do whatever I can to implement one. 
     One photo shows a bit of white plastic foam on top of a heat sink. 
Since the keyboard is so close, that foam can be used to press down on 
the sink for better contact with the IC when the keyboard is put back 
in place. With a Lumafix installed inside a white case 64, there is 
only a few millimeters between the top of the chip and the bottom of 
the keyboard. The underside of the keyboard acts like a shroud and
doesn't allow much airflow around it. That makes an effective VIC heat 
sink more important. Conventional ones with big "ears" will not fit.
     My photos show some ideas for new VIC heat sinks. They can be
attached to the chip with epoxy or at least some thermal paste for a 
good bond, and to the shield or base with epoxy so it will not fall 
off. If not securely attached somehow, that sink could short something 
in the computer. 
     If anyone wants me to install a Lumafix module, they will also get 
the best heat sinks I can fabricate for all the chips that need it. As 
always, I welcome questions and comments!

Ray