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TonyDuell · 21st Dec 2015, 5:58 pm

I have perhaps been lucky...

Worst I had was from a company that has been mentioned in this thread (and who, to be fair are normally very reliable and I have dealt with them many times). I bought some 1A thyristors in TO5 cans. When they arrived they were unmarked (!). I fitted one to an ancient telephone answering machine I was repairing, the control system of which consisted of many thyristors with turn-off capacitors between them trigger by things like incoming ring, end of announcement, etc Anyway, with said 'thyristor' fitted it didn't work at all, turns out it would never turn off. In the end I removed all drive from the gate to find it was still 'on' at power-on. To cut a long story short it turned out I had been supplied with PNP transistors in TO5 cans and the gate pull-down resistor was turning them on (OK, emitter and collector were technically the wrong way round, but when you have a 470ohm base resistor and a 15k collector load you don't need much gain....).

Of course the supplier refused to replace them (they have a 'no returns' policy) but to be honest the cost of the components wasn't the issue. It was the several hours I had wasted...

Perhaps the most amazing thing is that I was once looking for a custom ROM/RAM IC for an HP calculator. I found a supplier (you can guess where) who said they could supply it, I contacted them to ask for price and order quantity and they asked me what package I wanted it in. Given it only ever existed in one type of package I am guessing they would print the number I was asking for on any IC with the right number of pins and then when it didn't work would fall back on the 'you must have damaged it' line.

21st Dec 2015, 5:58 pm	#8
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,222	Re: Warning fake components I have perhaps been lucky... Worst I had was from a company that has been mentioned in this thread (and who, to be fair are normally very reliable and I have dealt with them many times). I bought some 1A thyristors in TO5 cans. When they arrived they were unmarked (!). I fitted one to an ancient telephone answering machine I was repairing, the control system of which consisted of many thyristors with turn-off capacitors between them trigger by things like incoming ring, end of announcement, etc Anyway, with said 'thyristor' fitted it didn't work at all, turns out it would never turn off. In the end I removed all drive from the gate to find it was still 'on' at power-on. To cut a long story short it turned out I had been supplied with PNP transistors in TO5 cans and the gate pull-down resistor was turning them on (OK, emitter and collector were technically the wrong way round, but when you have a 470ohm base resistor and a 15k collector load you don't need much gain....). Of course the supplier refused to replace them (they have a 'no returns' policy) but to be honest the cost of the components wasn't the issue. It was the several hours I had wasted... Perhaps the most amazing thing is that I was once looking for a custom ROM/RAM IC for an HP calculator. I found a supplier (you can guess where) who said they could supply it, I contacted them to ask for price and order quantity and they asked me what package I wanted it in. Given it only ever existed in one type of package I am guessing they would print the number I was asking for on any IC with the right number of pins and then when it didn't work would fall back on the 'you must have damaged it' line.