I finished my BM50 build last week and thought I would repay my gratitude in some way for the information from people that I have used to get this done.  Hopefully these steps, pics, and some of my comments help others who follow with a build of the OTS or HRM.  People who have posted pics and information about their builds here have been very generous.  Nik was very helpful when I emailed him with a couple of questions.
THANK YOU sduck who posted some very helpful pics of his recent BM50 build.
I also found some very good videos out there from tonymckenziecom on Youtube who built up an OTS.  These videos were very useful to help me figure out the order of things.  THANK YOU to him too (I don’t know if he is on this forum). 
I documented these steps to a friend of mine in email as I went along and they are kind of cut and pasted but hopefully everything makes sense chronologically.  This may take some kind of dubious record for longest post ever but I am hoping it helps someone.
Pre-steps - getting organized
Got the kit!  This should be interesting.  No instructions, just the layout.



The push/pull pot I got for volume/bright has markings on it that say
450T220K106B2F5..... or something close to that.  The layout calls for a 1MA pot, the 220K threw me off and I checked with Nik that I got the right part.  It is.

Caps, Resistors, and boards pre-organized (will double-check that I got these sorted right as I go).  This is not a job for the colorblind.  NOTE: The 190K should say 180K on my sheet.  This takes some figuring if you are like me and don’t have them all memorized yet…..




Step1 - chassis basics
Step 1 is complete, got all the basic pieces in place before the boards, trannies, and solderfest.  One thing useful to note that I had to figure out is the star washers should go inside the chassis between the nut and the component you are mounting, such as the board spacers or grounding lugs.

Step 2 - heater wires

“Heater” wires installed (kind of a pain but I think I got them twisted nice and clean).  I temporarily removed the on/off and standby switches to make it easier to operate on the power tube sockets.  DON’T forget to put them back on before you solder resistors to the sockets(like I did) or you will run out of space!  Also I dabbed some black paint on the chassis nuts to prevent loosening over time.  I am also taking care to twist the wires over the connection points prior to soldering per some advice posted out there on the interweb.  It takes extra time and use of my new forceps (should’ve been a doctor) but should prevent any bad connections when this thing sits on a cabinet cranked to 11.  Details baby!


Step3 - jacks and backside of chassis
I worked primarily on the input jacks and backside of the chassis today.

The input jacks were a pain.  Based on sduck’s pics in his BM50 build thread (thanks!), I attached them to the outside of the chassis to wire and then put them back in the right way. The black wires were shielded and confused me because the shield had to wire to part of the jack but it was unclear on the diagrams exactly what to do.  I sent an email last night to Nik at Ceriatone and he replied to clear me up.   The shield goes to the jack and in some other places will be grounded to the bus rod but does not connect to the other wire or at the other end.


Installed the side mounted boards.  There is a blank plate behind each board to prevent grounding to the chassis.  I put a nut in between each board to space it out a little so there is no pressure on the solder joints. Seemed like the way to go.  I don’t know if you can see it but my pirate eye patch is in the background.  I somehow scratched my eye with sawdust (building my cabinet) last weekend and it flared up on Sunday (ER visit, much pain, etc).  Yes, I wore goggles but something slipped in!  Basically I did quite a bit of the work up to this point with really poor (double) vision in my right eye.  Looks to be clearing up to almost normal soon luckily.


Installed caps and resistors for the preamp sockets. 


This little power tube rats nest was fun but the power sockets are 90% done until I get the main boards in.  The pot in the middle is for bias adjustment from underneath with the test points being the black and red things sticking up from the chassis.  That reddish thing is the ground selector switch but is says to keep it unwired, not sure why that is yet or if it could be useful.  I also wired up about half of the power and switch connections.  I really don’t like how the far left power and standby switches are really close to the power tube sockets.  I unfortunately couldn’t flip them because then the labels on the faceplate would be upside down.  I think Ceriatone changed these switches recently since they are different from the pictures on their site.  I would design it differently but for now be really careful not to short something.  I pity the roach that crawls into that area.  The diagram in the back with the red dots shows how I mark off the parts that I have soldered.


 

I ended this step by wiring up what I could on the preamp/poweramp jacks and speaker jacks.  The star thing in the middle is the impedance selector (4/8/16).  Very nice feature.



Step 4-front and sides

This is the front bus bar above the pots.  It is a single brass wire suspended in air as a common ground.  I had to levitate it magically before I started soldering.


This area with the deep, mid/boost, and rock/jazz switches is a bitch.   Every one of these tiny red connectors will have 1-3 wires in each of the six tiny holes.  There is no way to stick all those wires into them so creative looping of wires is in order to create more solder joints.  Also, I have burned up these guys before on other projects by getting them too hot so it is very sketchy work.  A couple of the small boards are now in the chassis too.  The one thing I need is a hot air blower to affix the heat shrink tubing when used.  The soldering iron at close range does the job okay but leaves them slightly deformed.

This is now on the side near the input transformer.  Notice the strategic loops so I can eventually wire more here later?  This most definitely will add to the tone as the electrons get drunk spinning as they figure out they are supposed to go.

The voltage regulator IC is now on the bottom of the chassis.


Pilot wire (white) for front light nicely twisted (use a drill top twist the wires is the trick, simply chock them in and slowly turn while keeping the other ends apart).

Front side pots and switches now ready for more wires.  A couple of the wires are loose and ready to solder to the main boards.  The small boards are installed.

The master, level, and drive pots.  The coax wires have that funky shield that get grounded.  These take time for sure to make nice.


Footswitch jack and switches to set controls to manual/footswitch.

I am done with capacitors and resistors so from here on out it is just wires and solder. There were two extra resistors in the kit, a 10K and 4M7, but for sure these were extra as they were not on the layout.  I’d rather have too many than not enough!  Well done on QC for the kit, I’ve had worse luck in the past with things like this.

Step 5 - transformers and choke
The transformer step was fairly easy and now I am ready for the two main boards and final wiring.  It now weighs a ton!
Bottom view

Top view before soldering wires

Top view after soldering everything possible.  I added some strategic silicone and cable ties to keep things tidy.



Output transformer wire bundle comes up through the chassis and goes to the impedance selector and speaker jacks.

Input transformer and side boards are all complete.  Main power, on/off switch and fuse are all connected.  If I plugged it in, I might actually get the light to come on but I am not going to try that quite yet.

Home stretch now......I just have to be patient and take my time to triple check everything.  I don’t want to screw something up by rushing. 
Step6 - main boards
First main board completed.  Very blurry like my eyes and head at that  point.

Second main board started.  Pick a wire, any wire.....

Testing and Debugging
Tested, debugged, internal trim pots adjusted, biased correctly, finished, finished, finished!
Not without a little bit of hacking late night (i.e. dawn) but I got it working and fine tuned things today. 
Final inside view.  After thinking I had it completed and it turned on, I hacked a bit and realized I forgot one wire (from volume knob...quite important) and one of the relay board chips was backwards but I figured it out.  The OD channel was also very weak at first but it turned out that I had to adjust the internal OD tonestack trimpots.  I took a lot of time to get it very clean and kept wires in parallel where possible.   The lack of any extra noise I think is the big payoff.


Final outside view

This amp is pretty darn nice.  Totally buzz free on the clean channel at very loud volumes, virtually buzz free even on OD at high volumes (I expect something to be there).  Wow, this amp blows me away and with a 1x12 cabinet loaded with a WGS 1265 it totally rocks even though my speaker is probably not even burned in yet!
Cabinet notes
I also built a custom wood 1x12 cabinet for it using a dovetail jig and biscuit joiner from Lowes (about $200 investment) and a lot of sanding.  I plan to get a planer and maybe a jointer if I do more of these but it worked out pretty well.  Next time I will definitely use ¾ plywood for the baffle and back instead of the thinner stuff I used but it still sings nicely.

Nice work. I like the cab. When I finished my first (OTS 183) I left a note of thanks here too but not in as much detail as yours. I'm almost done with my second OTS and I will say it's much easier. I did take the time to write up a build sequence and a make wiring diagram of the input lacks, which helped a lot.
By the way, the ground switch is a throwback to the old days before we had grounded (three wire) power cords. It would connect a capacitor to ground between either of the two power cord wires (the objective being to connect the cap to the grounded neutral wire) to reduce hum and reduce shock hazard. Now that we are using IEC type power sockets the switch isn't required. It's just there for show.

very nice! i am probably going to be doing my first build soon, either a tweed twin or a prinzetone. i kinda wish i had built my bluesmaster now, looks like it was alot of fun! beautiful cabinet work, too!

Gregg

Guilty as charged and my addiction is spiraling.  My particular progression has been guitars->pedal-kits->preamp kits(fivefish)->fixing my existing gear->this build.  Next likely step is more research/self education and a scratch build of some sort.