I purchased two Z84C0020PEC's that were also questionable. One was dead, one runs ok at 8mhz (I haven't tried faster clock speeds yet). They had identical top printing and date codes, but the molding marks on the bottom were different. The dead chip was replaced without question with one that also works fine at 8mhz.
Also a recent batch of TIL311's were used pulls (advertised as new) and 3/10 were dead in whole or part. They had shortened tinned leads and obvious signs of removal.
I could write pages about counterfeit capacitors - my primary hobby is vacuum tube audio gear. My experience is that 100% of Chinese capacitors are faked.
If Mouser or Digikey carries the parts it's worth the extra cost!
On 6/28/2014 10:44 PM, curt mayer wrote:
I've got a 8088 cpu blank, and a z80 cpu populated. I bought a 10 chip lot of z84c0002pec's from ebay, and was a bit horrified when I got them to find--that they smelled of new paint. identical fronts, but the backs showed different countries (indonesia and phillipines), all with different mold imprints.
so, I wired up a 20mhz test rig for the z80's, using a derivative of dunfield's no-ram monitor (i disassembled it and added a lot more code), and not a one testedout at 20 mhz. one limped at 16, 2 ran at 12, and the rest were good at 8. all tested as cmos: the out (C),F instruction sends FF, the nmos sends 00.
for 15 bucks, I got a bunch of mildly useful z80s of unknown actual characteristics.
anyhow, now i want to build the 8088 board with V20's - NEC has a part number for dip-40's at 16mhz. 70108hcz-16. lots of them available on ebay from china.
any experiences here before I become the ebay counterfeit chip crash test dummy?
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