Re: Looking for DECstation 3100/2100 or DECsystem 5100

On Wed, 9 Aug 2017, Felix Deichmann wrote:

> > I have two 3100s I've been hoarding, but I haven't been able to get the
> > serial cable right in the RJ style port to get console, or else neither
> > are working.  They're old enough that they likey need to be re-caped.
> 
> Need for re-capping is probable (also because DEC used so many
> "quarternary ammonium salt" caps like Chemi-Con low ESR 105 degC types
> in nearly all their power supplies).

 PMAX's H7821 PSU is indeed badly affected, especially the output filter 
Chemi-Con 1800µF/25V SXF parts, however the PSU has its base PCB mounted 
upside down and consequently the components leads up, resulting in caps 
being safe as long as the box has been stored in its operating orientation 
(it's the seal breaking causing these capacitors to fail).  Daugthercards 
have components mounted sideways, however their caps seem to be fine.

> I also saw that the DS3100 has a battery pack for RTC which runs the
> risk of leaking and destroying whole PCBs when too close/not taken care
> of. :/

 It's mounted in a holder attached to the enclosure and a bit away from 
the PCB, with the leads being the only way for leakage to reach the main 
board, reducing the risk somewhat, although not completely of course.

 It's a standard DEC 3xAAA NiCd 12-19245-01 part BTW, used in various 
systems.  I've used an off-the-shelf handset NiMH pack as a replacement a 
few times already, which is compatible enough not to require changing the 
plug even.  Ping me if you need help chasing a suitable part and I'll dig 
out the details or might even be able to get one for you -- I got mine 
from a high street store, so I don't have a trace handy, but I could pop 
in to the store again sometime this week and check.

> There were also pmax machines which refused to boot when the NVRAM
> battery was drained, but I think they were using "Dallas" RTCs with
> integrated cell.

 The PMAX firmware is very picky about diagnostic status and will not even 
get to the console prompt if there's any failure, including e.g. unplugged 
keyboard or mouse (even if the console is set to serial), or Ethernet.  
You'll have to press the Halt button to gain control in that case, but 
then you should be able to boot, as long as the boot device is operational 
that is.  Getting clean status instead might be preferable of course. :)

 HTH,

  Maciej