2 Nov
2017
2 Nov
'17
8:14 a.m.
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-bounces at classiccmp.org] On Behalf Of Aaron
Jackson via cctalk
Sent: 02 November 2017 14:23
To: cctalk at classiccmp.org
Cc: jnc at 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 at 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