Coleco Controller Chip socket confusion.

[stuartmcivor]

Hello, 

 

My Coleco has an intermittent problem. When starting a game the skill menu is bypassed, the game starts and the player moves to the right. Cycling the power on and off a couple times and the issue goes away; for a bit. From what I have read on the forum is it's likely the Octal Buffer(s) at U18 and/or U19 are on their way out. Forum advice says to replace them with Texas Instruments SN74LS541 and to socket them while in there. I have no problems sourcing the chips but I have no idea what sockets to use. The instructions say 20-pin IC sockets (0.3” spacing). I get the 20-pin part. The 0.3" spacing has me confused. Is that pin spacing, pitch, socket width. A link to a correct sized socket would be great. I did find a kit at Console5 but the shipping to Canada and the dollar exchange make it a last resort, not first try.

 

Thank you.

[nick3092]

If you are ordering from a parts warehouse like Digikey or mouser, it's the row spacing. You may see it noted as 7.62mm as well depending on the listing. 

[+mytek]

SN74LS541N (Digi-Key P/N: 296-1666-5-ND)

IC DUAL LEAF DIP SOCKET 20POS (Digi-Key P/N: ED3054-5-ND)

 

I use these sockets on my builds, and they give a very tight, secure, and positive contact to the IC chip. Some people like to install machine pin sockets instead but they're considerably more expensive and not very forgiving if the IC pins are not perfectly straight.

[leaded solder]

The "standard" pin spacing on a board that uses DIP parts is 0.1" (or 2.54mm.) Armed with that knowledge you can sort of guess that the 0.3" number is for row spacing, but I agree it isn't clear at all in the Digi-Key listing.

 

For 80s stuff, ROMs, static RAMs, video chips and CPUs tend to have a double-wide 0.6" row and 74s are almost always 0.3" wide.

 

I don't think I've ever seen a double-wide (0.6"/15.24mm) 20-pin DIP IC, but I'm sure they exist: Digi-Key sells some sockets for those too, although they're very expensive and out of stock.

 

You can also get cheap dual wipe sockets of all kinds of common sizes (including 20p) in a kit from Amazon, although Digi-Key has a much higher quality floor for their parts than Amazon. I use a kit like this (the one I actually bought is no longer in stock) primarily as an organizer for loose sockets and buy more from Digi-Key as I drain them building boards.

Edited November 15, 2023 by leaded solder

[stuartmcivor]

I did get it sorted out; sockets and replacement chips are in and everything seems to be working.

 

Originally I ordered a 66 piece assorted size sockets kit and it contained the two 20-pin sockets needed. I also had ordered a 10 count of SN74LS541N chips from AliExpress. Of the 10 only 2 worked correctly (thank goodness for the sockets). Not really pleased with that experience and skeptical of the 2 working chips I have since ordered from mouser.ca some reputable chips and sockets.

https://www.mouser.ca/ProductDetail/595-SN74LS541N

https://www.mouser.ca/ProductDetail/571-1-2199298-6

 

Thanks you for the tips and links.

 

 

 

[nick3092]

I've seen way too many reports of bad/fake chips from Ali express. I'm even weary of eBay. That's why I always order from a reputable supplier like Digikey or mouser.

[+dhe]

On 11/15/2023 at 11:31 PM, stuartmcivor said:

and everything seems to be working.

Replacing the 541, got your skills menu back?

[stuartmcivor]

Yes. And the controller no longer automatically moves to the right. Before the switch it wasn't every time the coleco was powered on that it skipped menu and messed controller. When it did happened I would turn the console off and on until it was normal. But it got more frequent.  After the switch it hadn't happened again.