Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Zippy Zapp
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by Zippy Zapp »

@banman,

Thanks for the kind words. I completely forgot to snap a picture of the board as it sat and didn't work right. It worked as a 512k but it didnt see the other chips. I couldn't fix it so I used my hot air station and removed the chips from the board. The pads all seem fine and I toned them out and they are good. I soldered one of the chips back in this time with the pads all filled with solder. While it was fiddly getting the chip lined up I was able to get it soldered back in much better then the first time.

This board was basically the first time I ever hand soldered an SMD RAM chip. I had worked with resistors and capacitors plenty but not an IC like this.

I think I still have a picture of it before but have to dig through my iPad as it is not on my phone. I am going to put the rest of the RAM chips back on when I get home today.
Can I ask Zippy Zapp, what brand of memory you used and where you bought them from?
I used a link that was provided on the github project page to an ebay seller. I forgot what brand they are. I want to say Toshiba. Made in Japan.

I know at least one of them worked because I was able to get 512k tested no problem. I also was able to test the Battery backup and it did indeed work. So it all boils down to my crappy SMD hack job and now that I have learned a better technique and have a better tip to use I should have no problem. I still have 4 more boards and enough parts to make at least 3. I think I just need more RAM chips.

I have NeoTunes on a disk I just have not tried it out as my board isn't fully working yet. That is one I want to try for sure.

Thanks!


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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Ok I finally fixed it. To answer the question above my chips are Hitachi. Some were made in Japan and some in China. They seem legit.

After I took all the RAM chips off the board I cleaned it up, tinned the pads and soldered them back on. This time it was cleaner although one of the ICs is crooked but it is still touching all the pads so I am going to leave my hack job alone. This was a prototype for me as a test for soldering these type of ICs. I failed pretty bad the first attempt but figured it out after that.

After testing with the RAM tests mentioned above and the GMT64 suggestion it works and checks out. Those chips can take some abuse because after my soldering then desoldering, dropping them, mangling the pins, rubbing them across carpet and my socks they still work. :lol:

Now I am going to order some proper boards with ENIG. I will see if I can get it beveled too but I am not going to use PCB Way I am going to pay much more and use OSH Park, because they are local here and I get them faster. Their quality is top notch but you pay for it.

It is interesting as I look at all my original C64 carts. Most of my 3rd party carts do not have beveled card edges. Not my Epyx Fastload, Super Snapshot's, Action Replay, Fisher Price carts and most others I have just don't have it. So I am not sure it is a big deal because if it was these cartridges would have damaged my C64 over the years for sure. My 1764 REU has a very, very slight bezel which you can barely detect.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Zippy Zapp wrote: Sat Sep 11, 2021 7:35 pm Now I am going to order some proper boards with ENIG. I will see if I can get it beveled too but I am not going to use PCB Way I am going to pay much more and use OSH Park, because they are local here and I get them faster. Their quality is top notch but you pay for it.
I had bad experiences with OSHpark. I had a batch of PCBs for GandALF from them and there were short circuits between traces and that ended up destroying a few of my precious XC9572XL CPLDs.

I had the PCBs for the prototype of my GeoRAM clone made at JLCPCB. They cost 2$ for 5 units then add 18$ to get ENIG but when you ask for ENIG, you can get thicker gold contacts for an edge connector for free AND beveling on that edge connector for free. This 18$ remains the same amount whether you do 5 or 50 boards!!

This makes it 20$US for 5 cartridge grade PCBs. Keep reading...

So lets say I now want 50 since the prototype worked fine. That's 20$ for 50 units then add 18$ to get ENIG and gold plated edge connectors and beveling. A total of 38$US for 50 boards with all the features required to make a top quality C64 cartridge PCB.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Ok cool thanks for the tip I will check out JLPCB because unlike everybody else on the planet I am not a huge PCBWay fan. I have used OSHPark for quite a few years and I haven't really had a problem, but yeah they are expensive. It cost me $35 for 3 boards. But some small stuff is only a few dollars. Not a place I would order large quantities though but for my use it has been fine.
I had bad experiences with OSHpark. I had a batch of PCBs for GandALF from them and there were short circuits between traces and that ended up destroying a few of my precious XC9572XL CPLDs.
That is a bummer. I will have to check my Super Snapshot repro boards because the one I built did not work and puts a black screen on the C64. I know all the chips work because I tested them so it can only be the GAL or the board itself.

With regards to JLCPCP how easy is it to order? One thing I like about OSH is that you upload either the gerbers, a kicad, .pcb or .brd and they figure most everything out for you. I am certainly not a wiz when it comes to all the PCB config details...
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Hi Zippy Zapp and eslapion,


This information you've provided is great! Thanks.

Great that you got your RAM cartridges going again. Well done!


A very interesting discussion.

I too put projects to one side for some time before I go back to them. It helps to get my thoughts in order and maybe think of new strategies.



Yes, I did get some OSH boards some time ago. I have never used JLCPCB, are they made in the US?
I see lots of great things for sale in North America. It is the prohibitive shipping costs to Oz that hamper things. Quite a number of Chinese vendors offer a free shipping service.

I think regarding PCBway they have a slick community hub and ordering system. For newbies like me they make it easy to part with my money.



Zippy Zapp wrote: Sat Sep 11, 2021 7:35 pm After testing with the RAM tests mentioned above and the GMT64 suggestion it works and checks out. Those chips can take some abuse because after my soldering then desoldering, dropping them, mangling the pins, rubbing them across carpet and my socks they still work.



Just to confirm, these are the RAM chips from the seller suggested on

https://www.hackup.net/2019/04/the-neoram-remix/


K6X4008C1F or HM628512

https://www.ebay.de/itm/5pcs-HM628512LF ... 01&mkevt=1


I will definitely have to try these out. I thought I was being smart with the RAM chips I used, evidently not.

I used Cypress branded 512K x8 CMOS static RAM modules. The data sheet had them down at a slightly lower operating current and they were cheaper.

https://www.cypress.com/file/43851/download


https://www.aliexpress.com/wholesale?Se ... 0705200957

So, I cannot recommend these Cypress RAM chips at this stage. They are just too difficult to reliably solder onto the PCB for me.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Just to confirm, these are the RAM chips from the seller suggested on

https://www.hackup.net/2019/04/the-neoram-remix/


K6X4008C1F or HM628512

https://www.ebay.de/itm/5pcs-HM628512LF ... 01&mkevt=1
Yep. Those are exactly the ones I bought. They are fiddly to solder. On my second attempt I did continuity checks on all pins after soldering 1 chip in place. I used a lighted magnifier type deal to examine all the pins. Even some that looked good actually didn't make contact because not all the pins were apparently even height. That is why I did continuity checks by touching the very top of the pin with the corresponding pad on the next RAM chip pads or the 74 logic chip as a few of the pins go to that.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

Post by banman »

Hi Zippy Zapp,


Thank you for that information.

Zippy Zapp wrote: Mon Sep 13, 2021 5:23 am Even some that looked good actually didn't make contact because not all the pins were apparently even height. That is why I did continuity checks by touching the very top of the pin with the corresponding pad on the next RAM chip pads or the 74 logic chip as a few of the pins go to that.
I had the exact same experience with soldering the SOIC 32 RAM chips I had.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Zippy Zapp wrote: Mon Sep 13, 2021 5:23 am They are fiddly to solder.
Use Rosin flux!
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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I used lots of flux. I use it in gel form and it comes in a large syringe. It's near impossible with out it.

@eslapion,

Do you test your PCBs before you solder the components on? How would I test something like the NeoRam or Super Snapshot PCB?

I usually just assume they did that when they made it but clearly I am wrong.
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Re: Building a NeoRam Ram expansion memory cartridge for the C64 computer

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Zippy Zapp wrote: Mon Sep 13, 2021 11:40 pm I used lots of flux. I use it in gel form and it comes in a large syringe. It's near impossible with out it.
There are different types of flux. Rosin flux is usually not available in syringe. This older kind of flux is messy but it does a much better job.

Just make sure you remove it either with real flux remover or a mixture of 98% pure alcohol and 2% acetone. Only pure alcohol will just spread the stuff.
Do you test your PCBs before you solder the components on?
For a few pennies JLCPCB does that for me. On a PCB, every trace has to be considered a node as per Kirchoff's law so every node has to be checked for continuity and for shorts with every other node.

For a normal person, checking that takes hours. JLCPCB has a machine which does it in a few seconds.
How would I test something like the NeoRam or Super Snapshot PCB?

I usually just assume they did that when they made it but clearly I am wrong.
Never assume. I wrecked projects back around 2008 because Multifor did a mess of a few PCBs. Today they are out of business.

Checking for continuity and shorts is almost always an optional service which costs extra.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders
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