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V64jr Stability Mod

 
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cpsystem3



Joined: 07 May 2013
Posts: 24

PostPosted: Fri Jul 16, 2021 1:26 pm    Post subject: V64jr Stability Mod Reply with quote

Just wanted to share my V64jr stability modification that I made last week. It came out aesthetically pleasing and functionally rock solid.

I found information on an old defunct N64 scene website claiming the V64jr was unstable (the internal ram corrupts easily). They called out that the V64jr derives 3.3v (for DRAM and Logic) by using two in series diodes to drop regulated 5v down to APPROXIMATELY 3.7ish volts. The voltage is not only unstable (it fluctuates) but it is also on the threshold of the ram ICís operating tolerances.

I am an arcade circuit board collector for another hobby. A common technique used by bootleggers is to use two diodes to drop 5v down to 3.3v logic levels. The ďcircuitĒ that Iíve seen in the past is identical to what I found in the V64jr.

The solution: remove the voltage dropping diodes (D1, D2, D4 and D5) and install a proper 3.3v regulator. Run the output of the 3.3v regulator to the output of the diodes that were removed. These days, you can pick up AMS1117 3.3v regulator PCBís off of eBay, pre assembled, for about $2. As seen in the photos attached, I piggy back the 3.3v regulator onto the 5v filter capacitor (for 5v input) and run a single fly wire supplying the TTL logic and the Ram stick directly.

The result is rock solid stability. I have left my V64jr powered for over 24/hr and the ram integrity remains intact!

Like my DS1 post, I hope this info helps someone else in the future to enjoy their V64jr!



2FCB4FCC-A2B7-4C0E-9A2B-0E9FD68BEEA2.jpeg
 Description:
Doctor V64jr
 Filesize:  118.39 KB
 Viewed:  322 Time(s)

2FCB4FCC-A2B7-4C0E-9A2B-0E9FD68BEEA2.jpeg



A112BCEE-8AC9-4F39-80E4-4E35182B000A.jpeg
 Description:
Add the AMS1117 voltage regulator PCB to the solder side of the V64Jr.
 Filesize:  147.52 KB
 Viewed:  322 Time(s)

A112BCEE-8AC9-4F39-80E4-4E35182B000A.jpeg



0D0DC6B5-4BFC-479D-AD4F-6246EAA3E961.jpeg
 Description:
Remove D4 and D5 from the V64jr Main Board
 Filesize:  53.77 KB
 Viewed:  322 Time(s)

0D0DC6B5-4BFC-479D-AD4F-6246EAA3E961.jpeg



DF06643F-D51E-4B60-B8BA-FA9B28205529.jpeg
 Description:
Remove D1 and D2 from the DRAM stick.
 Filesize:  58.97 KB
 Viewed:  322 Time(s)

DF06643F-D51E-4B60-B8BA-FA9B28205529.jpeg



E82CE170-DFB6-49A7-A0A2-FD628ECDAAD2.jpeg
 Description:
Connect the 3.3v fly wire to the output of the removed diodes D5 and D1
 Filesize:  182.6 KB
 Viewed:  322 Time(s)

E82CE170-DFB6-49A7-A0A2-FD628ECDAAD2.jpeg


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Mystic_Merlin



Joined: 15 Oct 2007
Posts: 418
Location: Bangkok

PostPosted: Sun Jul 18, 2021 3:12 pm    Post subject: Reply with quote

Is this the website you were mentioning?
http://n64.icequake.net/
I came across it a few days ago, that would be a fun coincidence.

It has the schematics for the PPA adapter for the CD64 and lots of other goodies.

I've never been into the N64 tbh, even though I went all the way to HK golden shopping center back in '96 to pick up the CD64, I didn't use it much but well, it's good to see this type of information is still alive somewhere on the net.
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cpsystem3



Joined: 07 May 2013
Posts: 24

PostPosted: Sun Jul 18, 2021 5:25 pm    Post subject: Reply with quote

That is exactly where I found the info:

http://n64.icequake.net/mirror/slaanesh79/Backup_Units/V64jr/V64jr.htm

Whoever runs that website is doing a great service. There are countless defunct websites archived there, files and all.

I hadnít been into the N64 stuff until recently. I was curious about the units back in the day, but couldnít afford them. Theyíre fun to tinker with now! Funny you mention golden shop. I clearly remember their website, and always just assumed it was a scam, haha,
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CZroe



Joined: 29 Aug 2021
Posts: 9

PostPosted: Sun Aug 29, 2021 5:26 pm    Post subject: Reply with quote

Mine always seemed stable (original owner) until I tried to use it again last year with a Bung Multi Xchanger. I dug up my old print out of the stability mod and was preparing to do it when I got hit by an EF-4 tornado earlier this year and my printout was flooded in the basement. I did find the same archived instructions but the images are nearly impossible to make out. Obviously, I have to prioritize more important things in the aftermath of the tornado but I still plan to do this. Thanks for modernizing the mod!

My typical usage scenario back in the day was to power the jr512 from the N64 console while I transferred the game, then switch to battery power momentarily while I cycled the N64ís power. I know now that flipping the switch off after booting wasnít necessary but I still do it so that I donít forget and run the batteries dead after powering off the console.

I got the Multi Xchanger 5 years ago and the majority of transfers to the jr512 now result in a black screen even with a quality power supply. Itís corrupting immediately during the power switch or during the transfer but it doesnít seem to corrupt during gameplay if you get it to boot. Itís presumably stable when powered from the console but Iíve only got that far a few times ever.

Around 2014 I used batteries to shuttle a game from a work (PC still had a parallel port Wink). I recall that worked so maybe Iím dealing with another issue entirelyÖ like bad reads from the PlayStation drive.
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