TI 99/4a Video Ram Replacement

[Sayonara!]

I'm having some issues with the vram on the ti-99/4a. I have figured out that chip 5 is bad and needs a replacement. I've failed to find a replacement online, does anyone have a link to a replacement chip for this? what I can read on the chip is NEC 8245DF400. Thanks in advance

[+arcadeshopper]

If you look in the FAQ you will find information on this, I have ram in my store it's 4164 which is easily modified (or use one of the boards I sell to drop in with it) 

4164 runs cooler and lasts longer and is easier to source 

[Ed in SoDak]

16 hours ago, Sayonara! said:

what I can read on the chip is NEC 8245DF400. Thanks in advance

That's the date code, 45th week of 1984. The chip is a 4116, in stock about $4 each at Jameco Electronics for example. Jameco should have a low-cost first class mail shipping option. Bummer for small orders from them, there's a $10 surcharge on orders less than $20.

 

There's other places too, I saw at least one listing on ebay. Just be aware some parts sourced from China can potentially be bogus relabeled chips. It's best to order from a US company with a good reputation of long-standing.

 

Or the 4164 can be substituted with modification as arcadeshopper says.

Edited April 17, 2022 by Ed in SoDak

[Sayonara!]

4 hours ago, Ed in SoDak said:

That's the date code, 45th week of 1984. The chip is a 4116, in stock about $4 each at Jameco Electronics for example. Jameco should have a low-cost first class mail shipping option. Bummer for small orders from them, there's a $10 surcharge on orders less than $20.

 

There's other places too, I saw at least one listing on ebay. Just be aware some parts sourced from China can potentially be bogus relabeled chips. It's best to order from a US company with a good reputation of long-standing.

 

Or the 4164 can be substituted with modification as arcadeshopper says.

Thanks, I just ordered a 4116 chip off eBay and am going to replace the bad chip on the ti

[mvancopp]

23 hours ago, Sayonara! said:

I'm having some issues with the vram on the ti-99/4a. I have figured out that chip 5 is bad and needs a replacement. I've failed to find a replacement online, does anyone have a link to a replacement chip for this? what I can read on the chip is NEC 8245DF400. Thanks in advance

I bought some from this place and all the chips worked fine and were in really good shape.

Texas Instruments - TMS4116-15NL - IC, Memory. DRAM, 16,384 Bit. (electronicsurplus.com)

 

Edit: I just checked and they still have > 400 in stock.

 

Edit2: Another place but you may need to buy 24 for 28+ sh. I haven't purchased for this place.

4116 RAM Set of 24 (arcadeshop.com)

 

Mark

Edited April 18, 2022 by mvancopp
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[XLERB]

On 4/17/2022 at 1:08 PM, arcadeshopper said:

If you look in the FAQ you will find information on this, I have ram in my store it's 4164 which is easily modified (or use one of the boards I sell to drop in with it) 

4164 runs cooler and lasts longer and is easier to source 

4164 works just fine!

[+Ksarul]

On 4/17/2022 at 9:38 PM, mvancopp said:

I bought some from this place and all the chips worked fine and were in really good shape.

Texas Instruments - TMS4116-15NL - IC, Memory. DRAM, 16,384 Bit. (electronicsurplus.com)

 

Edit: I just checked and they still have > 400 in stock.

 

Edit2: Another place but you may need to buy 24 for 28+ sh. I haven't purchased for this place.

4116 RAM Set of 24 (arcadeshop.com)

 

Mark

I've bought a lot of good things from Electronicssurplus.com in the past. Among other things, I bought a few hundred hexbus controller chips from them a few years back, probably the entire NOS supply of them on Earth.

[JJB]

Just adding info to this topic as I have just replaced my QI 4116's with 4164's. I had given my non-QI console the same treatment in the past but found removing the original RAM's and replacing them with sockets a royal pain the backside. This time I decided to snip a couple of 4116 pins and piggyback the 4164's on top:

 

- snip 4116 pin 1, 8 and 9 as close to the chip as possible and bend the PCB side remnants out of the way

- fold 4164 pins 1, 8 and 9 back on the top of the chip

- lightly tin 4116 pins with fresh solder, making sure the pad solder melts too

- lightly tin 4164 pins 

- piggyback a 4164 on 4116 (this is the fiddly bit) and when you're happy with its position, solder 1 4164 pin to its 4116 mate.

- solder the remaining pins; with a little bit of fresh solder on your iron, start from the PCB pad and work your way up.

- solder a small length of stiff connecting wire to the PCB remnant of pin 9 

- connect the other side of the wire to pins 8 and 9 on top of the 4164, taking care the wire doesn't touch any other pins.

 

I did 1 chip at the time, checking for the familiar start screen in between to see if all pins were properly connected (giving the 4164's a little twist at the same time).

 

Jochen