2 Nov
2017
2 Nov
'17
6:25 a.m.
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
2 Nov
2 Nov
7:22 a.m.
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 
8:04 a.m.
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.
A 555 can also take a Commodore PET down because it's solely in charge of
the RESET circuit, and no RESET == no PET.
On 2 November 2017 at 14:22, Aaron Jackson via cctalk <cctalk at classiccmp.org
wrote:
> 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
>
--
adrian/witchy
Owner of Binary Dinosaurs, the UK's biggest home computer collection?
www.binarydinosaurs.co.uk
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
2382
days inactive
2382
days old
3 comments
4 participants
participants (4)
-
aaron＠aaronsplace.co.uk -
binarydinosaurs＠gmail.com -
jnc＠mercury.lcs.mit.edu -
robert.jarratt＠ntlworld.com