How to fix your Doctor V64 Junior 512mbit.

"How to fix your V64Jr512 (by Socketz)

I have a V64Jr512, so I don’t know if my solution will work with any other model.

I had a lot of trouble with my V64Jr512 and after considerable effort, found out why and was able
to fix it.
I tried EVERYTHING! I disassembled it, changed the common components like the 74HC245s,
solder plated the cartridge edge connector, solder plated the memory edge connector, (very
carefully) soldered the memory to it’s socket, (again, very carefully) soldered the Altera chip to its
socket, added thermal dissipation to the Altera chip, then changed the memory SIMM socket and
the Altera PLCC socket, but NOTHING OF THIS WORKED!
I also tried changing the memory with some SIMMs, but discovered the V64Jr512 uses a custom
made memory SIMM. No, it’s not a standard DRAM SIMM, and it’s not a standard EDO memory
SIMM.

Then I noticed the following:
If I sent a game to the V64Jr and immediately verified it, it checked ok.
If, after sending a game to the V64Jr I left it on for some time (I tested mine for half an hour), then
verified it, the memory was still ok.
Finally, if I sent a game to the V64Jr, then plugged it into the N64 and turned it on, after a short
time (less than 5 minutes), the game crashed. After turning the N64 off and verifying the game, I
found out the memory had failed.

WHY? What’s the difference???
I used a tester to measure the voltage while battery powered and then while powered by the N64
and found a very slight difference… nah, can’t be that stupid…

IT IS!!!!

******** The V64Jr512 uses 3.3 Volt memory ********
The designers at Bung just took the 5V coming out from the 7805 voltage regulator, put 2 diodes
in series to drop the voltage to something less than 4V and fed the memory with this!
Why? Well, that’s easy, it was cheaper than adding a 3.3V voltage regulator. How much? Oh,
about $1.50 cheaper! You can’t believe it? Me either!

Let me tell you something: 3.3V memory requires 3.3 Volts, NOT 3.9V nor 3.2V.
IT REQUIRES THREE POINT THREE VOLTS!!!
This is a design flaw!

Well, let’s fix it… "

Read the rest of this in the original pdf file written by Socketz here: FixYourV64Jr512.pdf