Fairchild 670 DIY In Progress

[bockaudio]

Having worked on at least a few 670's over the years, if you want stereo, be sure to match two things besides the tubes, which often NOT matched in real 670's:
the meters- if not matched you'll end up with different amp gains.
the UTC input xfmr.
You won't have to worry about the triads as they are made so well that I have seen little deviation withing a model #.
I met an engineer much older than myself a few years ago, and told me the old engineer's jo0ke about UTC. It doesn't stand for United Transformer Company. It's U Take Chances.

 

[CJ]

thanks for the meter info!

utc was pretty good in the early days but the quality did get a little loose towards the end,

the A-10/HA-100X secondaries are probably their best work, nobody does the side by side/foldback stuff better than they did,

i am going to use smaller teflon wire for the 6BA6 rewire as the 18 ga cloth was kind of messy for the 6386 wiring.

better tube sockets will be used, the ones in there now kept loosing pins out the bottom, i hatre when that happens,

happy holidays and wire safely!

 

[emrr]

I met an engineer much older than myself a few years ago, and told me the old engineer's jo0ke about UTC. It doesn't stand for United Transformer Company. It's U Take Chances.

All the old guys say that, don't they?  I've heard it many times. 

 

[CJ]

back in action on the 670,

laying out the chassis for the UTC A26 using a template, bout time, eh?

can not wait for JJ 6386 issue to be resolve3d, gonna go for the 6BA6,

then the Triads go on and then we will take a pic and all that, 

 

[CJ]

ok, UTC A26,  mounted and balanced, as it is a split core jobby,

Triad HS 50 going on next,

 

[CJ]

Triad holes are easy, just say "1/4 inch off the center line", from then on it is strictly eyeball, no time for silly templates when you can just drill a piiot hole then "walk the dog" with a bigger bit to correct, Triad actually leaves you some margin for error, unlike the small UTC stuff.

 

[CJ]

ok this thing is startin to look like something, gonna flip it over and hook up some wires and stuff,

maybe those things are on backwards?  :

however, looks good in the photo so wtf, over?

still have to wind some UTC Y-6431, have to do it on nylon, too many turns of fine stufff to do a layered job,

can still pass signal with the iron i have now, so tuning up the front end should be an eventuality,

if you want a sleeper off evilbay, go for the Triad 2543 = HS 52, jus sayin...

can somebody photoshop me some A-33 shields over the A-26 iron? 

 

[DaveP]

CJ'
Are you an early riser or an all nighter!?!
best
DaveP

 

[gary o]

Just perving over the pix of this beast shes th iron maidon, love it !

 

[CJ]

no sleep til Hammersmith with this project,

just installed another transformer. took me 3 tries to get the right size,

see the two Hammond's sitting on the rail?  120/6.3 tapped?

they are a bit too big, but the 166N6 drops right in.

oh well, you can never have too much iron laying around,

i think the only reason that Rein and Alexandoravich did not add more iron is they ran out of room! 

gonna strip  down some tube turrets and rewire for 6BA6, this will save about a thousand bucks so if it only takes a few days, we are still making bank,

we can wind that pesky choke that everybody moans about, "runs too hot, wrong voltage drop, incorrect model number" and all that stuff,

lower lumbar L-3 is acting up, gonna get a small fork lift so i do not have to turn left and cough,  :-*

 

[jackies]

Paging dr. CJ, wtf over?
What's the holdup with this mother of all projects?
:

 

[RuudNL]

What happened with the Fairchild project?
Is it working now, or did it cause a 'big bang'?! 

 

[CJ]

going to do the 6BA6 version,

so i ripped out all the 6386 wires and sockets and am working next on the new tube sockets, i have a ton of military 6ba6 tubes, so this thing will be online for 2014, if i don't get hit by a train or or get eaten alive by a jungle chipmunk,, 

 

[jackies]

That'd be one Christmas miracle!

 

[buildafriend]

Please avoid the jungle chipmunks..

I need build threads like this to gawk at or ill lose my mind in the reality of all of my unfinished projects.

 

[marc11657]

Happy New Year CJ!

I too am starting on the journey of replicating a FC670! Nice to know I'm not the only one I've just been reading your interview with Rein - Really interesting stuff! I was wondering if it would be possible to upload an audio file of that conversation? Lots of great information in there that should be archived for everyone to hear.

 

[marc11657]

Does anyone know if the FC670 is exactly 14" high as the official manual states? I read somewhere that the sum for working out 19" rack unit height is:

h=(1.750n - 0.031)

N is the number of units. if the FC670 does indeed take up 6u of rack space then its actual height would be 10.469 inches. Am I cocking this up somewhere? Or is the FC670 an 8u beast, making its actual height 13.969?

Any input would be appreciated!

 

[mdainsd]

It is an 8U piece of equipment, 14" tall for all practical purposes. I too intend on building a period correct re-creation. Thats one reason I joined here. There are some very talented people here, this thread being a great example. Im looking forward to seeing this build completed.

Im taking a slow approach. First collecting every piece of documentation I can fine along with photographs.

I have started hunting NOS original parts, A real task but I also enjoy the hunt. i dont plan on starting any construction until the parts pile reaches critical mass. The tubes will be the "easiest" to acquire, so I'll hold off on them. Unfortunately some things like vintage caps are probably a non starter as even NOS ones from the 50's have deteriorated. So some compromises will have to made. The pile is growing pretty well.

Im in process of laying the chassis out in the sheet metal suite of SolidWorks. If it gets the green light its just an email to the sheet metal shop down the street and pick the pieces up a week later.

Im trying to refrain from asking questions until I really get stumped, which will happen.

Anyrate, back to this thread....Hows the progress?

Inquiring minds want to know.

 

[ereder4]

Sounds like an awesome project. Nebraska surplus has the vector standoffs, if you haven't already sourced them.

http://www.surplussales.com/Inductors/Ind-SlugTu/Ind-SlugTu-6.html

 

[mdainsd]

Thank you very much for the lead! But fortunately I ran into a stack of NOS 9 pin vectors early on in the search. Now about those pesky original VU meters in mint condition....