Also from HP 98xx repairs and also from other hp computer equipment. About 50 or more defective 74hxx and 74xx. I'll try to make a list this weekend. In my experience 74h have a larger failure rate the the 74 series H08 , H4x and 7412x the highest. -Rik -----Oorspronkelijk bericht----- Van: "Rik Bos" <hp-fix at xs4all.nl> Verzonden: ?12-?2-?2015 00:12 Aan: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Onderwerp: RE: Failed ICs and components Kile, I've a lot defective 74xx's most of them having hp numbers. Date range 72-80. But the ic's are located in the Netherlands. If you're interested contact me off-list. -Rik -----Oorspronkelijk bericht----- Van: "Kyle Owen" <kylevowen at gmail.com> Verzonden: ?11-?2-?2015 23:57 Aan: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Onderwerp: Failed ICs and components I am writing my master's thesis on accelerated life testing and would like to get a collection of parts to decap and experiment on. What prompted my study is a failed 7474 dual flip-flop in a PDP-8/E. As I later read (on here, I believe) was that the 7474s seem to fail in higher number than other 7400-series ICs. Is this because of a design flaw? I'm not sure (yet), but would like to find out. More recently, I saw a 680k 2W carbon resistor that read 1.3 meg out of circuit. As it turns out, it was in a high voltage portion of the circuit, and I suspect that electromigration caused its failure over time. Many of you are probably already aware that carbon resistors tend to increase in value as they age, though there are a few explanations too for that behavior, as I understand it. I would like to tie all of this together by researching older accelerated life testing schemes, examine how those parts actually fared, and see how current day models might be improved. If anyone has a collection of dead ICs (preferably those that have died inexplicably, and not by extreme overvoltage, for instance), I would like to talk to you about getting a few. If they are 7474s from Texas Instruments, ca. early 1970s, even better! Thanks in advance, Kyle

On Wed, Feb 11, 2015 at 5:16 PM, tony duell <ard at p850ug1.demon.co.uk> wrote: That sounds quite promising. I am looking forward to doing some life testing on newer devices as well. ARGH! It is a pity you didn't ask for this about 3 months ago. I had kept Darn! That sounded like a good collection. Alas, I know I haven't kept every bad IC either (except that one from the PDP-8/E...not really sure why until now, I guess). But if you do find them, I could certainly use them. Kyle

On 2015-Feb-12, at 12:49 PM, Chuck Guzis wrote: Well, just a data point, but I've never had to replace an IC in my ca-1970 HP2116, composed of hundreds of SSI chips, 80-90%of which are CerDIP. They're mostly CT?L, with some TTL, however. (It's had one quad-pack core driver transistor failure.) For that age and number of ICs, that's pretty good. Contrast even with other HP equipment.