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<div class="content-title">
<a href="https://fritzm.github.io/power-fixes.html"><h1>PDP-11/45: Power fixes and CPU debug</h1></a>
Mon 30 May 2016
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>Connected up the aforementioned red wire hack to the new power harness, and verified +5V to slots 10 through
15. Console is no longer all address and data lights on, but basic console load address / examine / deposit
operations are still not working. A random assortment of address lines seem stuck, different on each power
cycle. About the only thing that reliably functions from the console is loading the two highest address bits
from the switches immediately after a reset. Pulled the floating point unit, unjumpered the DD11 expansion
backplane, and removed all peripherals except the M792 diode ROM; same (broken) behavior...</p>
<p>Scoped all the DC voltages, and did not notice any glitches. Pulled the H742s for some bench work: verified
AC LO and DC LO signaling on both units, replaced a broken Mate-n-Lok connector on one of the units, blew out
dust from all the 5V regulators and replaced their indicator bulbs with modern equivalent (CM7381). Sourced
and put on order a modern equivalent (OL-6003BP) for the indicator bulbs on the -15V regulators.</p>
<p>Next steps will be to verify various Unibus signals on the backplane, then maybe play some swap games with CPU
card spares to see if I can get closer to a working console as a starting point. All I have time for this
weekend, though; sorry nothing new to see so no new pictures this time!</p></div>
<hr />
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<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/initial-power-on.html"><h1>PDP-11/45: Initial Power On!</h1></a>
Sun 08 May 2016
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>Beeped out the new harness to check for shorts or incorrect pins, then plugged in just the H742s and fired it
up. All the DC regulator modules seem to be working, and I was able to trim them up to nominal voltages at
the CPU end of the harness. The indicator lamps on all but one of the DC regulators seem to be burned out,
though, so I put some new lamps on order (at last for the +5V regulators; a modern equivalent for the -15V
regulators is tougher to find).</p>
<p>Given that success, I plugged in the CPU side of the harness, took a deep breath, and powered on! Hmmm. No
detonations or smoke, but all data/address/mode lights lit (see below), which is not right... Front panel
lamp test and data address mode switches and indicators are working though at least.</p>
<p>Some investigation on the backplane turned up no +5V to slots 10 though 15, which could be part of the
problem. Ah, that's what the mysterious clipped red wire soldered to the backplane might have been about
(visible in the top right <a href="https://fritzm.github.io/images/pdp11/kb11a-backplane.jpg">here</a>...) Sure enough, some inspection
shows the corresponding trace on the backplane looks burnt! I could hack this red wire into my new harness I
guess, but I'd rather remove it and try to repair the board trace with a shunt. So the backplane will have to
come out. I guess that's what I get for not investigating the weird red wire and for not beeping out the
power distribution on the backplane before mounting and populating it...</p>
<p><img src='/images/pdp11/initial-power-on_thumbnail_tall.jpg' title='Initial power on! No smoke, but all lights on (not right). Well, it's a start!' onclick='pswipe("pdp11",27);'/></p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/power-harness-2.html"><h1>PDP-11/45: Power Harness, continued</h1></a>
Sat 23 April 2016
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>Moved the power modules and partial harness back over to the racks today, got everything remounted, finished
and dressed the backplane terminations, and completed the inter-H742 connections.</p>
<p>I did not do the runs for the backplane memory to the lower H742, as I do not have any backplane memory. I
probably won't ever have any, either: these memory options are specialized to the '11/45, are quite rare, and
only cover part of the available address space. Additionally, they would require me to track down the details
of a backplane ECO to do the corresponding parts of the harness correctly. The core and MOS memory that I do
actually have are all system-unit options anyway.</p>
<p>Here are some pics of the in-rack wiring in progress, and a couple views of the finished harness. If you add
up the capacity of the DC modules, you'll see that an '11/45 like mine (with floating point) is provisioned
with +5V at 100 [sic] amps, and -15V at 20 amps. That's no joke of a power supply...</p>
<p><img src='/images/pdp11/harness-progress_thumbnail_tall.jpg' title='Finishing up the replacement power harness in the rack' onclick='pswipe("pdp11",24);'/>
<img src='/images/pdp11/harness-complete_thumbnail_tall.jpg' title='Completed power harness from above rear' onclick='pswipe("pdp11",25);'/>
<img src='/images/pdp11/power-supplies_thumbnail_tall.jpg' title='Completed power harness from side' onclick='pswipe("pdp11",26);'/></p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/power-harness.html"><h1>PDP-11/45: Power Harness</h1></a>
Sun 17 April 2016
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>The main bit I'm missing from the '11/45 is the power distribution harness; somewhere over the years this was
misplaced, or maybe I accidentally gave it away along with some excess '11/40 parts. In any case, I haven't
had any luck tracking one of these down (made extra difficult by the fact that my '11/45 is an early model
which requires a slightly different harness than more recent models), so I'll have to build one myself from
scratch.</p>
<p>Luckily the required harness is pretty well documented in the engineering print sets. The crimp pins are
standard Mate-n-Lok still in production. Some of the connectors are out of production, but they haven't been
too hard to track down.</p>
<p>Here are some pictures of the amassed wire of appropriate gauges and colors, connectors, crimp pins, and the
start of the harness build on the bench:</p>
<p><img src='/images/pdp11/harness-parts_thumbnail_tall.jpg' title='Wire, connectors, and crimp tool to get started on replacement power harness' onclick='pswipe("pdp11",22);'/>
<img src='/images/pdp11/harness-bench_thumbnail_tall.jpg' title='Partially completed replacement power harness' onclick='pswipe("pdp11",23);'/></p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/ebay-parts.html"><h1>PDP-11/45: Some parts from eBay</h1></a>
Sat 09 April 2016
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>I've been keeping an eye on eBay and have collected a few more goodies: a DD11-D nine-slot expansion
backplane, a fully populated (128K x 18-bit) MS11-L MOS memory board, and a couple of replacement BC08-R
cables for connecting the console to the CPU cards. The MS11-L is a bit of a luxury; I am figuring it will be
easier to deal with during bring-up than the core memory systems I have on hand. It will also be nice to run
with a full address space.</p>
<p>Below is an updated shot of the CPU chassis with the expansion backplane installed, populated with bus
jumpers, terminators, grant continuity cards, the MS11-L memory, a DL11 serial interface, and an M792-YB
bootstrap ROM. I've gone ahead and slotted in the FPU in the first four slots, since the cleaned and
refurbished CPU cabinet is probably the safest place to store them now. Console cables are also installed:</p>
<p><img src='/images/pdp11/boards-in-chassis-2_thumbnail_tall.jpg' title='Backplane and expansion populated with CPU, MMU, FPU, bootstrap ROM, console serial, 256K RAM, grant continuity cards and terminators' onclick='pswipe("pdp11",19);'/></p>
<p>The M792 ROM is an interesting bit, and probably worth a comment. This is a 32-word diode-matrix ROM card.
The bits are physically laid out on the card (see pictures below); where there is a diode, there is a logical
1 bit and where there is the absence of a diode there is a logical 0 bit. Typically the matrix would be
loaded with a bootstrap program, to save the operator from having to toggle it in from the console on each
boot.</p>
<p>The program could be modified by physically adding or removing diodes in the matrix. My card has had such a
mod; there is a handwritten note attached from some engineer describing this. The mod customizes the
bootstrap to always load from an RK disk unit, to avoid having to toggle in the device address at boot. I
will probably revert this mod because I like having things in fairly stock/usual condition.</p>
<p><img src='/images/pdp11/mr11-with-note_thumbnail_tall.jpg' title='A modified M792-YB bootstrap ROM, with a vintage note attached' onclick='pswipe("pdp11",20);'/>
<img src='/images/pdp11/mr11-bare_thumbnail_tall.jpg' title='M792-YB bootstrap ROM with note removed' onclick='pswipe("pdp11",21);'/></p>
<p>For fun, here's the source listing of the stock bootstrap. You can match the octal digits of the machine code
against the diodes in the ROM above (low word addresses at the top of the matrix, and least-significant-bits
on the left).</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
2
3
4
5
6
7
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9
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11
12
13
14
15
16
17
18
19
20
21
22
23
24</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="nt">173100</span> <span class="nt">013701</span> <span class="nt">MOV</span> <span class="o">@</span><span class="p">#</span><span class="nn">177570</span><span class="o">,</span><span class="nt">R1</span> <span class="o">;</span><span class="nt">READ</span> <span class="nt">SWITCH</span> <span class="nt">REG</span> <span class="nt">FOR</span> <span class="o">....</span>
<span class="nt">177570</span>
<span class="nt">173104</span> <span class="nt">000005</span> <span class="nt">BEGIN</span><span class="o">:</span> <span class="nt">RESET</span> <span class="o">;</span><span class="nt">FORCE</span> <span class="nt">CLEAR</span> <span class="nt">IF</span> <span class="nt">RETRY</span>
<span class="nt">173106</span> <span class="nt">010100</span> <span class="nt">MOV</span> <span class="nt">R1</span><span class="o">,</span><span class="nt">R0</span> <span class="o">;...</span><span class="p">.</span><span class="nc">DEVICE</span> <span class="nt">WC</span> <span class="nt">ADDRESS</span>
<span class="nt">173110</span> <span class="nt">012710</span> <span class="nt">MOV</span> <span class="p">#</span><span class="nn">-256</span><span class="o">,</span><span class="p">@</span><span class="k">R0</span> <span class="p">;</span><span class="nt">SET</span> <span class="nt">TO</span> <span class="nt">READ</span> <span class="nt">256</span> <span class="nt">WORDS</span>
<span class="nt">177400</span>
<span class="nt">173114</span> <span class="nt">020027</span> <span class="nt">CMP</span> <span class="nt">R0</span><span class="o">,</span><span class="p">#</span><span class="nn">177344</span> <span class="o">;</span><span class="nt">IS</span> <span class="nt">IT</span> <span class="nt">DECTAPE</span><span class="o">?</span>
<span class="nt">177344</span>
<span class="nt">173120</span> <span class="nt">001007</span> <span class="nt">BNE</span> <span class="nt">START</span> <span class="o">;</span><span class="nt">NO</span><span class="o">.</span> <span class="nt">GO</span> <span class="nt">TO</span> <span class="nt">START</span>
<span class="nt">173122</span> <span class="nt">012740</span> <span class="nt">MOV</span> <span class="p">#</span><span class="nn">4002</span><span class="o">,</span><span class="nt">-</span><span class="o">(</span><span class="nt">R0</span><span class="o">)</span> <span class="o">;</span><span class="nt">YES</span><span class="o">.</span> <span class="nt">MOVE</span> <span class="nt">TAPE</span> <span class="nt">TO</span> <span class="nt">FRONT</span>
<span class="nt">004002</span>
<span class="nt">173126</span> <span class="nt">005710</span> <span class="nt">TST</span> <span class="p">@</span><span class="k">R0</span> <span class="p">;</span><span class="nt">WAIT</span> <span class="nt">FOR</span> <span class="nt">ERROR</span><span class="o">!</span>
<span class="nt">173130</span> <span class="nt">100376</span> <span class="nt">BPL</span> <span class="p">.</span><span class="nc">-2</span>
<span class="nt">173132</span> <span class="nt">005740</span> <span class="nt">TST</span> <span class="nt">-</span><span class="o">(</span><span class="nt">R0</span><span class="o">)</span> <span class="o">;</span><span class="nt">IS</span> <span class="nt">IT</span> <span class="nt">ENDZONE</span><span class="o">?</span>
<span class="nt">173134</span> <span class="nt">100363</span> <span class="nt">BPL</span> <span class="nt">BEGIN</span> <span class="o">;</span><span class="nt">NO</span><span class="o">.</span> <span class="nt">TRY</span> <span class="nt">AGAIN</span>
<span class="nt">173136</span> <span class="nt">022020</span> <span class="nt">CMP</span> <span class="o">(</span><span class="nt">R0</span><span class="o">)+,(</span><span class="nt">R0</span><span class="o">)+</span> <span class="o">;</span><span class="nt">ADJUST</span> <span class="nt">POINTER</span>
<span class="nt">173140</span> <span class="nt">012740</span> <span class="nt">START</span><span class="o">:</span> <span class="nt">MOV</span> <span class="p">#</span><span class="nn">5</span><span class="o">,</span><span class="nt">-</span><span class="o">(</span><span class="nt">R0</span><span class="o">)</span> <span class="o">;</span><span class="nt">NOW</span> <span class="nt">START</span> <span class="nt">ACTUAL</span> <span class="nt">READ</span>
<span class="nt">000005</span>
<span class="nt">173144</span> <span class="nt">105710</span> <span class="nt">TSTB</span> <span class="p">@</span><span class="k">R0</span> <span class="p">;</span><span class="nt">WAIT</span> <span class="nt">FOR</span> <span class="nt">DONE</span>
<span class="nt">173146</span> <span class="nt">100376</span> <span class="nt">BPL</span> <span class="p">.</span><span class="nc">-2</span>
<span class="nt">173150</span> <span class="nt">005710</span> <span class="nt">TST</span> <span class="p">@</span><span class="k">R0</span> <span class="p">;</span><span class="nt">ERROR</span> <span class="nt">ENCOUNTERED</span><span class="o">?</span>
<span class="nt">173152</span> <span class="nt">100754</span> <span class="nt">BMI</span> <span class="nt">BEGIN</span> <span class="o">;</span><span class="nt">IF</span> <span class="nt">SO</span> <span class="nt">START</span> <span class="nt">OVER</span>
<span class="nt">173154</span> <span class="nt">105010</span> <span class="nt">CLRB</span> <span class="p">@</span><span class="k">R0</span> <span class="p">;</span><span class="nt">FOR</span> <span class="nt">DECTAPE</span><span class="o">,</span><span class="nt">STOP</span> <span class="nt">TRANSPORT</span>
<span class="nt">173156</span> <span class="nt">000137</span> <span class="nt">JMP</span> <span class="o">@</span><span class="p">#</span><span class="nn">0</span> <span class="o">;</span><span class="nt">GO</span> <span class="nt">TO</span> <span class="nt">ROUTINE</span> <span class="nt">LOADED</span>
</pre></div>
</td></tr></table>
<p>Hmmm, the Pygments syntax highlighting package used by my blog generator doesn't seem to grok MACRO-11; may
have to do something about that...</p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/vt52.html"><h1>PDP-11/45: VT52</h1></a>
Sun 03 January 2016
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>Spent some time reviving a VT52 that I intend to use with the PDP-11. This was a pretty nice eBay find.
There was some oxidation and flakiness with the connectors to the chargen ROM daughter card (I remember this
being typical of VT52s even back in the day). A little more difficult to track down were some flaky solder
joints around the clock chip. But, everything else seems to be in pretty good shape and its working well now!
Here it is hooked up to a Linux VM on my macbook, compiling some LSST code to generate some output as a test
drive:</p>
<p><img src='/images/pdp11/vt52_thumbnail_tall.jpg' title='VT52 hooked up to a Linux VM for a test drive' onclick='pswipe("pdp11",17);'/></p>
<p>Man, seeing that funky font again, with its non-descending-descenders, is really great! Surprisingly, it
doesn't seem to be available in digital format anywhere, unlike the later VT100 fonts, etc. Try as I might, I
couldn't seem to find the chargen ROM listing in any of the DEC documentation archives, either.</p>
<p>Well, I do have a Digilent FPGA eval card and some level conversion chips laying around, so as a holiday hack
project I put together a quick ROM scanner in Verilog, interfaced it to the VT52 chargen on a breadboard, and
scanned out the contents. Here's a picture of the scanner in action, and the produced output:</p>
<p><img src='/images/pdp11/rom-scanner_thumbnail_tall.jpg' title='Homemade FPGA ROM scanner used to read out the VT52 character generator ROM' onclick='pswipe("pdp11",18);'/></p>
<p>The yellowish board on the right is the VT52 chargen. The Verilog source for the scanner, the scanned data,
and some preliminary attempts to convert the data to a few modern font formats are available on my github over
at <a href="https://github.com/fritzm/vt52">https://github.com/fritzm/vt52</a>. I need to learn some more about font formats to make some better font
files; if I do I will update that repo. Any help from fontophiles gladly accepted!</p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/backplane-and-logic.html"><h1>PDP-11/45: CPU Backplane and logic</h1></a>
Fri 03 July 2015
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>Mounted the CPU backplane, and slotted in the CPU and MMU logic cards. The empty slots on the right are for
the FPU -- I have those on hand but figure I'll wait to slot them until I've got the basic CPU up and running.</p>
<p>One kind of interesting thing: the logic boards were stored vertically for several decades, and on some of the
cards with plastic ribbon-cable connectors the plastic seems to have flaked and shed and fallen down the
boards. The flaky substance then grew some impressive crystals between some of the solder traces. Scrubbed
these out with some anhydrous IPA.</p>
<p>A tip copied from a fellow restorer: Alconox detergent for removing grime from various plastic components.
Parts soaked overnight come out looking nearly new (here you can see the cleaned plastic card guides).</p>
<p>Also pictured here are the characteristic bloody knuckles that are obtained whenever wrestling with PDP
backplanes, logic cards, and terminators in close confines. That really takes you back...</p>
<p><img src='/images/pdp11/boards-in-chassis_thumbnail_tall.jpg' title='CPU and MMU logic installed. Empty slots on the right are for the FPU.' onclick='pswipe("pdp11",13);'/>
<img src='/images/pdp11/board-with-crystals_thumbnail_tall.jpg' title='Logic board with crystals after several decades of storage' onclick='pswipe("pdp11",14);'/>
<img src='/images/pdp11/crystals_thumbnail_tall.jpg' title='Closeup of crystals on logic board' onclick='pswipe("pdp11",15);'/>
<img src='/images/pdp11/knuckles_thumbnail_tall.jpg' title='The characteristic bloody knuckles that are obtained whenever wrestling with PDP backplanes, logic cards, and terminators in close confines' onclick='pswipe("pdp11",16);'/></p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/panel-and-742s.html"><h1>PDP-11/45: H742s and front panel</h1></a>
Sun 21 June 2015
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>The H742 supplies are now back together, mounted in the cabinet, and wired through to the 861. I've powered
them up and run them for minutes at a time (without any DC regulator loads) and there have been no surprise
detonations...</p>
<p>The repainted cabinet side door has also been remounted.</p>
<p>Spent some time on the front panel as well. Removed the tubular lock and took a trip to the local locksmith
to have a new key made up. Replaced all the incandescent indicator lamps with the closest modern equivalent.
Panel is now remounted and it's starting to look like a real '11!</p>
<p><img src='/images/pdp11/742s-mounted_thumbnail_tall.jpg' title='H742s and CPU cabinet remounted' onclick='pswipe("pdp11",11);'/>
<img src='/images/pdp11/front-panel_thumbnail_tall.jpg' title='Front panel remounted -- starting to look like a real PDP-11!' onclick='pswipe("pdp11",12);'/></p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/fans-and-h742s.html"><h1>PDP-11/45: AC power and cooling</h1></a>
Sun 07 June 2015
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>Spent a lot of time over a couple weekends cleaning and reconditioning all the muffin cooling fans for the CPU
cabinet and power supplies. As you can see in the photo below, there are a lot of these! All reassembled
now, and wired along with the back-of-cabinet power distribution board. Also did a clean on the big box fan
at the top of the rack, not seen here.</p>
<p>I have also completely torn down the H742s to give them a thorough clean, touch up a few last corrosion spots,
and replace the failing neon indicators.</p>
<p><img src='/images/pdp11/chassis-with-fans_thumbnail_tall.jpg' title='CPU cabinet with restored cooling fans' onclick='pswipe("pdp11",9);'/>
<img src='/images/pdp11/742-rebuild_thumbnail_tall.jpg' title='Deeper into the H742s for cleaning, sanding, and painting' onclick='pswipe("pdp11",10);'/></p></div>
<hr />
</div>
<div class='article'>
<div class="content-title">
<a href="https://fritzm.github.io/power-controllers.html"><h1>PDP-11/45: H742 power control boards</h1></a>
Sat 23 May 2015
by <a class="url fn" href="https://fritzm.github.io/author/fritz-mueller.html">Fritz Mueller</a>
</div>
<div><p>Found a little time to clean up and go through the power control boards for the H742 supplies. They are
looking pretty good. Even the big electrolytics seem fine on first look. These things were built with very
high quality components, and they really seem to last and last.</p>
<p><img src='/images/pdp11/pwr-ctrls_thumbnail_tall.jpg' title='H742 power controller boards' onclick='pswipe("pdp11",8);'/></p></div>
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