Well, it has been mentioned a number of times in threads recently about this problem...
I now have to return chips for the 2nd time in the past few days... I've been trying to find some good working GI AY-3-8913 chips to fill 5 Mockingboard clones I've built. So I need a total of 10 chips. I bought 4 from a vendor on Aliexpress, none of the four worked. I protested, they sent me a return label so they're on their way back and hopefully I get a refund. I also ordered two from a vendor on eBay... same, neither work. And I've tested all these chips in multuple Mockingboards that work with known good chips.
It's annoying and a huge waste of time. Unfortunately for a lot of these chips there isn't a whole lot of alternative. For these there may be one, albeit one that requires some serious work. The AY-3-8913 is a 24 pin chip. GI also packaged the same core in 28 and 40 pin versions. I have two AY-3-8192 which I am pretty sure are good, but will need an adapter made to work in a Mockingboard. I also have a whole bunch of File KC89C72 and Winbond clones of the AY-3-8910 (the 40 pin verson). Those chips are more readily available and cheap enogh they are less worth Chinese time to fake. The clones were made more recently because they were widely used in things like slot machines up until a few years ago. So anyway, now I guess I have to take on the task of designing an adapter board so I can use the 40 pin chips I have in Mockingbaords designed for 24 pin parts. Surprisingly for Mockingboards the other chips needed are all easily available. The 74LS05 isn't that surprising I guess, neither the LM386 since those are a generic amplifier chips. But the 6522 you'd think would be harder. However, I have bought several large batches off Aliexpress and only run into one or two bad chips out of dozens. I suspect that some are re-labeled "MOS" or "Rockwell" and may be some other cheaper verson like UMC or WDC W65C02 (which were still made up until recently and are still in stock at some places). I guess maybe 6522 and some other chips like 82C55 were used widely enough there are still tons of them around.
I kind of suspect a lot of these fake large package chips are somehing like defective EEPROMs or something fairly cheap like that (if cheap enough maybe even working ICs, just not what is being paid for). When put in a socket intended for a device like these sound chips they just do nothing, but don't really cause any damage because power and ground pins are normally somewhat standardized. Its possible too I suppose that there's just nothing at all in the package.
Yeah, it's terrible. I'm trying to find EPM7128STC100 CPLDs and I bought a batch from AliExpress last december. They are all bad chips. And, like you said, it's a huge waste of time. You need to assemble your board, check your solder, program, see that it doesn't work, re-check everything and re-program to make sure, see that it still doesn't work, desolder the chip, clean the PCB, and repeat everything.
What makes it even worse is that when you finally decide to buy another batch from another vendor, it takes a month to get it (at least here in Canada).
The surprising thing with the bad EPM7128STC100s I got is that they can be programmed without problem. But with a logic analyzer and an scope, I see it's not doing what it's supposed to do.
I have bought several small batches from different vendors, this time on eBay. They won't be here before April, though. I can't wait to know how many will be good. In my case, being able to get a few good ones is not enough; it's for the IOU / MMU replacements. I must find a reliable supply of good ones.
I've been told that it wasn't like that until more or less recently. I wonder why it's different now. The supply of these old chips surely can't be the victim of changing geopolitics?
Define recently, just for reference. Just curious.
This document from 2010 already shows the widespread issue and its one I reference from time to time as it's very well written and illustrated. https://nepp.nasa.gov/docs/etw/2010/08_Hughitt_Counterfeit%20Electronics%20-%20All%20the%20World%27s%20a%20Fake.pdf
My Mockingboard project is dead in the water too thanks to fake chips. Every 6522 I've bought from eBay or AliExpress has been fake and defective. Demoralizing.
Yes I also have the experience with some DM9368 for my Hex Display kits. Always test them all before I assemble kits. I even got blocked by a seller on eBay because I made too much complains, which were of course legit. Sometimes complete batches are defect or fake. When 5% is defect it is the best I got so far.
In post #1, 'softwarejanitor' wrote:
" But the 6522 you'd think would be harder ..."
Uncle Bernie comments:
Try "Surplus Sales of Nebraska" for the 6522:
https://www.surplussales.com/Semiconductors/IC-5.html
From this page you can see their 6522 is $0.75 ea. at qty 1. These are pulls. For that price, no reason to complain.
- Uncle Bernie