In my case the PSU where I had this still does not work. It is a H7140 from a PDP-11/24. I found the failed 555 after help from a list member, but when I replaced it and powered on there was a big bang (I should have told you that!). I have never been able to repair this PSU and I need someone who really knows what they are doing to repair it as I think it is beyond me.
Regards Rob > -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Aaron > Jackson via cctalk > Sent: 02 November 2017 14:23 > To: cctalk@classiccmp.org > Cc: j...@mercury.lcs.mit.edu > Subject: Re: H7861 PSU issues > > Thanks! It was very satisfying and not the worst thing to go wrong for a > beginner. > > I was also quite surprised that such a simple component would die, and what I > find more confusing is that it died while I was using the machine. > > Aaron. > > Noel Chiappa via cctalk <cctalk@classiccmp.org> wrote: > > > > From: Aaron Jackson > > > > > Picked up a few 555s and sockets and now it works! > > > > Congratulations! > > > > It's odd that a 555 failed, but sometimes there's no rhyme or reason > > to what fails. E.g. I was fixing some broken M7859's (KY11-LB > > Programmer's Console), and on one of them a 7493 (4-bit counter) had > > died. That's not one of the 'problem' 74xx chips, like ISTR the 7474 being? > > > > Noel