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Repaired: Bung DS1 Super Doctor Save Card

 
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cpsystem3



Joined: 07 May 2013
Posts: 24

PostPosted: Fri Jul 16, 2021 1:03 pm    Post subject: Repaired: Bung DS1 Super Doctor Save Card Reply with quote

Hi everyone!

I’m a long time lurker of these forums and big fan of Tototek and Tony’s offerings! Recently I pulled out my Backup Unit collection and picked up where I left off, about a decade ago. Between repairing what has failed over time, and adding new oddities, it’s been a fun time.

The other day, my Doctor DS1 SRAM save cartridge (for the V64 and V64jr) was acting quite strange. For those who don’t know, it’s a battery backed sram emulator / manager for use with SRAM save based N64 games. It has 2MB of static ram, an altera CPLD to drive the memory, and a CR2302 battery to make the sram non volatile.

The fault: I was able to flash the sram successfully using the EvekIII tool on an old laptop. Once the data was loaded into the ram, I could successfully use the DS1manager homebrew tool to “backup” and “restore” the data to one of the 5 slots. Games would pickup the save no problem. Everything seemed just fine … UNTIL I went to save my game with the N64 itself. The game would show a success message, but the reality was it was simply just deleting the data! I was chasing my tail for a bit, thinking it may be due to unstable power or a failing battery. It was not.

Not sure where else to turn, I decided to start my repair by changing out the sram (Sony CXK581000). Given the simple nature of the cart, it was either a sram or CPLD fault. If the CPLD went bad, the unit was garbage as dumps are not publicly available. In the end I lucked out! The SRAM had indeed gone bad. Swapping in a new pair got the save emulator back on track (PC and N64 can both save data now).

Hope this info helps someone down the road!



2A87023A-3096-4613-A659-69EE51ADBB75.jpeg
 Description:
Sram CXK1000
 Filesize:  122.49 KB
 Viewed:  1740 Time(s)

2A87023A-3096-4613-A659-69EE51ADBB75.jpeg



7F216C3A-4C59-4E91-AEFD-4863CE43B1C5.jpeg
 Description:
DS1
 Filesize:  98.27 KB
 Viewed:  1740 Time(s)

7F216C3A-4C59-4E91-AEFD-4863CE43B1C5.jpeg


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CZroe



Joined: 29 Aug 2021
Posts: 18

PostPosted: Sun Aug 29, 2021 5:36 pm    Post subject: Reply with quote

Nice fix! I took apart my DX256 Super Save Card the other day and was surprised to find that it has a battery with a Windbond W24010S-70LE SRAM chip. Still reading just over the “3v” it is marked with and works perfectly.

I was just trying to disable the emulator function. Bridging the pads does not let me boot carts inserted into the top. There are some unpopulated footprints on the board and I have to wonder if only early units could switch between being an V64 Emulation Adapter or not. I have one from 1997 and one from 1999 and am the original owner for both but I can only find this one after a tornado came through and wrecked everything. I believe it’s the later one.

Edit: OK, it realize now that I also needed to remove the 10k resistor when I bridge the jumper pads. Done and now the DX256 works with original games. Smile
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CZroe



Joined: 29 Aug 2021
Posts: 18

PostPosted: Thu Sep 09, 2021 11:18 pm    Post subject: Reply with quote

In the days that followed I also opened my DS1 and found it was an early unit with at least a few bodge wires and a couple cut traces. I delicately reassembled it but realized a few days later that it was no longer working.

There are two places where the bodge wires connect to traces that go straight to the edge connector. The solder mask was removed and the original traces were cut leaving only a thin trace to solder to and BOTH bodge wires had somehow worked loose… despite my careful handling earlier. I isolated the edge connector with kapton tape before I tinned and fluxed the traces. Then I soldered the wires back down and now it works perfectly. They both pass through vias and at least one connects to the same chip leg as another jumper wire so you definitely don’t want to accidentally flow the other side.

In LaC’s Jet Force Gemini cracktro he laments that his DS1 no longer works after taking it apart so I wonder if he was dealing with the same thing!
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