20 Nov
2014
20 Nov
'14
11:33 p.m.
There is no printset that I am aware of the for the H7864 PSU. I have a dead one of these
too, I do know which component failed but I don't know *why* it failed. As part of
that diagnosis I have made a partial schematic of a couple of parts of the boards.
The schematic for the Primary Control Module is here: http://1drv.ms/1yBzYTN (png) or
here: http://1drv.ms/1xFXUnR (Eagle schematic). I may not have drawn it logically, and may
have some bits wrong, as it is quite difficult to derive the schematic and it is easy to
make mistakes. I don?t know how to identify zener diodes, so all diodes are drawn as
ordinary ones. I was also unable to draw the transformers correctly as I don't know
their spec and pinout.
Regards
Rob
-----Original Message-----
From: cctech [mailto:cctech-bounces at classiccmp.org] On Behalf Of Jacob
Ritorto
Sent: 21 November 2014 05:46
To: General Discussion: On-Topic Posts
Subject: Re: 11/73 (ba23) bringup after 12 years in deplorable storage
conditions
Well, things inside were clean and pretty minimally configured, so, with all
apologies, I jumped the gun and applied power, but I'm afraid the old girl just
didn't survive the twelve years of temperature transients.
The illuminated ba23 power rocker switch lights up, but that's absolutely it.
No fans, no familiar power supply squeal, no drive spinup, nothing on the
seven-segment CPU state display on the rear. Seems thoroughly dead.
I guess I need to start tearing it down and debugging the power supply as I
recall that it was at least doing more than this before the years of bad storage.
So I need to find power supply diagrams and start tracing things out, right?
Any ideas as to where to begin?
On Thu, Nov 20, 2014 at 4:34 PM, Jacob Ritorto <jacob.ritorto at gmail.com>
wrote:
> Good deal. I guess I'm just gonna go for it after a cursory
> inspection and dusting. It has stayed utterly dry; just the temp and
> dust were concerns. I'll report back in a while.. Thanks!
>
> On Thu, Nov 20, 2014 at 3:55 PM, Ian S. King <isking at uw.edu> wrote:
>
>> At the very least, take a good long look at the power supply and its caps.
>>
>> Has the storage, as bad as it's been, been dry? If not, you'll
>> almost certainly have corrosion all over the place, especially in the
>> fastons ISTR run power to the backplane. (I haven't looked at my own
>> 11/73 in a few years, but it's in a dry, temperature-stable
>> basement.)
>>
>> Best of luck! - Ian
>> On Nov 20, 2014 12:32 PM, "Jacob Ritorto" <jacob.ritorto at
gmail.com>
>> wrote:
>>
>> > Hey all,
>> > I've been getting the bug worse and worse to start working on a
>> > real pdp11. The Raspberry Pi / simh emulation is fantastic, but my
>> > hunger
>> for
>> > authenticity is becoming rampant. I haven't run the youngest in my
>> fleet
>> > of pdp11s, the 11/73, since circa 2002 and if I recall correctly,
>> > it was becoming flaky and popping out to ODT inexplicably from time
>> > to time
>> back
>> > then (I think this is the one with the notoriously combustible
>> > power
>> supply
>> > wires that probably haven't been ECO'd yet -- need to get to that
too).
>> > It's been lying in a warehouse in western Pennsylvania with no heat
>> > and
>> a
>> > lot of dust. So, worst case, we're talking temperature transients
>> around
>> > 110 F and -20 F with no protection. It did stay quite dry.
>> >
>> > Think it'd be bad to simply blow the dust off and fire it up?
>> >
>> > thx
>> > jake
>> >
>>
>
>