The AM Forum
March 29, 2024, 02:00:36 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: T-368 Saga & Update  (Read 8182 times)
0 Members and 1 Guest are viewing this topic.
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« on: December 11, 2006, 10:52:17 PM »

Decided to do "a few little things" on the RF deck this afternoon, while reading the mail on 75.

Department of nothing goes smoothly.

Well, let's poke around and see what's what, maybe how the new vacuum variable will fit? At least I didn't drop it.

First let's pull this 70 amp fuse that is JS'd into the spot and looks very much like it goes from B+ to ground. Does it? Really? Uh huh. WTF? Well, that came out ok... we're cruisin now. 

(btw, that's a bad sign... wonder if something else got really fried as a result of this little bit of cleverness - time will tell...)

Wait a sec, this nut on top of the ceramic standoff is loose, the strap is loose and it looks like it has been moved so it is like 1/4" from ground. Let's fix that... ummmm... nut spins with the threaded rod, and if I try to spin the nut off with a driver, it twists the strap. Grab the micro pump pliers, grab the nut behind the nut, and 10 minutes later, voila! Take the standoff apart, clean, reassemble, re-route the strap.

QSO is in full swing on 3885.

Wait a sec, there are a whole bunch of other connections that are loose down here too... hmmm...

Ok, well, let's pull the front sub panel with the Loading & Tuning gear train and see what we can see about the front end of the PA area - besides, we'll need to have it out for cleaning & painting, lubing the gear train, getting at the mounting for the new vacuum variable loading cap, and also to move some of the RF parts around, including pulling the big arse mica blocking cap...

First step, gotta remove the set screws from the bellows style coupling of the Tuning cap. Well there are 4 and 3 of them look shiny, like they have been replaced. No prob, we'll hit 'em with some penetrant, select the proper allen wrench, and pop 'em out.

No way. They're no size known to man. Tried the metrics, the US , nothing is exact!! Bizzare. Well I only need to pull a PAIR!!

The QSO has moved down to like 3825 by now... Brent is channel master.

Ok, so how the heck are we gonna get these stinkin' set screws OUT without destroying the bellows coupler??

It's a brass coupler... fwiw.

So, here's the plan... we'll take the next size up allen wrench and with a nice little hand stone of the right size and grit, take it down one face at a time until it just taps into the allen set screw - then we'll pull it out!

Many iterations later, grind and test, it's just right... I mount the key into a T handled tapping handle for control and torque (keep in mind this is like a 6-32 size set screw here), tap tap tap, into the set screw. TWIST - ahhhh! Out it comes.

Now the next one... Same method... tap tap tap, TWIST. sssttrrrriiiipppp!!

Friggin setscrew is dead soft crap.

I HATE allen set screws!!  Angry

what to do now??

The dremel with flexible extension hangs to my right... obviously for good reason... find the right drill, chuck it in, drillllllll, lube with some kero, drilllllllll, lube, drilllllllll, lube, drilllllllllll... etc... the QSO has ended, I move back up to 3885 and 4s, 5s and 9s are heard... take out the little mill/burr mount it in... gonna have to take it flat down to the shaft of the vacuum variable - what's that shaft made out of any how?? would be nice to know when I'm down to the shaft... burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube, burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube,burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube,burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube,burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube,burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube,burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube,burrrrrrrrrrrrr, lube, burrrrrrrrrr, lube... looks good. Twist? no. Pull? no. Wedge? no.

back in with the burr, must have missed some, but it is moving a little, pivoting around the set screw area... burrrrrrrrrrrrr, lube, burrrrrrrrrr, lubeburrrrrrrrrrrrr, lube, burrrrrrrrrr, lubeburrrrrrrrrrrrr, lube, burrrrrrrrrr, lubeburrrrrrrrrrrrr, lube, burrrrrrrrrr, lubeburrrrrrrrrrrrr, lube, burrrrrrrrrr, lube... grab the shaft of the vacuum variable with a thin nosed vise grip, twist the front panel knob, YESH!!!

Ok, now undo the screws holding the sub panel with the gears & knobs, lift out, and yes it comes out!

Nice.

Meanwhile the clock has been rotating...

take the gear/counter assembly off the front panel, remove the set screws from the two knobs, lube gears, twist knobs, all good and smooth!

Ok, why not pull the rest of the knobs from the front panel and see what the paint looks like under it all... find the allen wrench of choice, uh-oh, the setscrews in these knobs are really siezed. Not a good sign. But, we'll finess it, not too much torque - don't want any more stripped ALLEN set screws!!  Shocked

Let's drop some penetrant down the screws first, yeah.
These are those military style "Raytheon" knobs, black plastic, two set screws.
Bad news after 50 years, steel set screw in an aluminum inner collar.

Wait a bit, clean up the bench a little after the last operation, give the lube some time to work its way in...

<tick tock, tick tock>

Find a really GOOD allen wrench, tight fit... ehhhhhh, pop! Next screw... ehhhhhhh, pop! Ok!  Cheesy

On a roll now! Three more knobs, really at the limit of the wrench's holding power, but they break free... now the last knob! Well... two set screws. Try one... well that one does not want to go, AND it feels like the screw head is giving up - you know that feeling? Those rounded flats??

Try the other one, hope the penetrant works... ok! pop! Back to the stuck one. No way... <ponder>
What the heck to do... don't want to kill the knob, because it is skirted and I don't have any in that style skirted. Oh joy!

The QSO has died down, the band gone into noise and fades... dark outside.

Well, let's take a worn down abrasive cut off wheel, chuck it on the dremel, and make a slit across the set screw, drop in a small screw drive and pull the screw that way! The slit will be on the bottom of the knob anyway, and later we can find a replacement! OK!!

Bzzzzzzzzz... nice slit.

Screwdriver... nice fit.

Twiiiiiisssssst... crack! Angry

End of the setscrew breaks off.

Now no choice, major knob surgery. Take out the model sized hand saw, cut away and remove the section around the set screw, re-cut the slit into solid screw, relube, insert screw driver, Twiiisst! Voila!

Now, let's gently remove the skirt, and reapply it to one of the new knobs... push, push push around the perimeter... ahhh here it comes! CRACK! crud. Ok, we'll use solvent cement and fix it... off it comes.

Solvent cement applied. Find the new knobs... crud they don't have the little lower ring to mount the skirts!!  Tongue

The End.

            Or, why everything takes much longer than it should and 100x longer than you can imagine it in.

                             _-_-WBear2GCR
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
W1ATR
Resident HVAC junkie
Member

Offline Offline

Posts: 1132


« Reply #1 on: December 12, 2006, 12:53:11 AM »

I was kind of wondering what that house mains fuse was doing in there in this pic. How about a pic of the bottom of the deck showing where the fuse was. There should be a 500puff doorknob,(blocking cap), tied between the tune vac top and the high b+. Maybe he confused a 500pf/5kV DK cap with a house fuse. Shoot, anyone can do that. Roll Eyes

Other than that, it looks like your having fun already, and this is just getting started. Tongue



* fuse pic.jpg (61.14 KB, 640x480 - viewed 705 times.)
Logged

Don't start nuthin, there won't be nuthin.

Jared W1ATR


Click for radio pix
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4620



« Reply #2 on: December 12, 2006, 07:05:29 PM »

Bear, you need to invest in a good set of Bristo (aka Bristol) wrenches if you're gonna F around with ol' military gear.

Those weren't Allen screws  Grin

I'm currently going thru a 75A2 that has a mixture of Allens, Bristos, and regular screw head set screws.  The PTO coupler had one Bristo and one Allen  Angry
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
W1EUJ
Guest
« Reply #3 on: December 13, 2006, 05:42:07 PM »

BEAR,

 If you want to, you can replace the Bristol setscrews with Hex. McMaster-Carr carries a wide selection
of setscrews. They also carry the Bristol type, if you wanted to keep the rig 'original'.

I'd do the hex. The rig will have, what, 1-2 more owners over its lifetime? Perhaps one more
cleanup or restoration? Make it easy for the next guy.

Dave
W1UEJ
Logged
WA1GFZ
Member

Offline Offline

Posts: 11152



« Reply #4 on: December 14, 2006, 12:27:01 PM »

Back in L88 days the Chevy note said tighten the spark plaus a bit before you remove them so a burr isn't formed to trash the thread.
I've learned to do this with anything screwed into aluminum.
Also a rap with a punch will break things loose before you stress a screw slot or allen.
Antiseize everything
Logged
The Slab Bacon
Member

Offline Offline

Posts: 3934



« Reply #5 on: December 14, 2006, 12:56:16 PM »

Back in L88 days the Chevy note said tighten the spark plaus a bit before you remove them so a burr isn't formed to trash the thread.
I've learned to do this with anything screwed into aluminum.
Also a rap with a punch will break things loose before you stress a screw slot or allen.
Antiseize everything


Frank
         I like to use blue locktite on anything steel into aluminum. It locks it down, and also seals the threads so they wont sieze in place. especially in a wet / damp environment. Its good schtuff!! You will ALWAYS be able to get it apart!

                                                        the Slab Bacon
Logged

"No is not an answer and failure is not an option!"
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #6 on: December 15, 2006, 09:55:04 PM »

ATR, if you go back to my first thread on the T-368, which was "Canadian Marconi" - since I only knew what the guy had told me at first, and he thought it was Canadian Marconi, I explained that somehow it was sitting in there where the Loading cap was supposed to be!!  Shocked Shocked Shocked Shocked Shocked Shocked

 Shocked Shocked  No possible reasonable explanation. As far as I can see it is (was now) connected between the B+ and ground!!

No Bristol visible or found yet in the rig... fwiw. Phew!

Although Bristol probably strip out less than Allens...

Yeah, couldn't tighten or loosen the allens on either the bellows (I'll cut a new hole and thread it... no big deal) or on the knobbers.

Only the knobs have aluminum... so far.

Now the main question is what/how to STRIP the bloodly paint with - it is chromated aluminum for the front panels, and then what to use for paint...  and SOON!!

Do not want to remove the chromate, because then It'd have to be rechromated to take the paint or else I'd have to hit it with aircraft type two part deadly fume paint (nice finish tho' !)...

... the "paint strippers" in the stores are so weak that they barely work... so thinking about putting the panel inside a plastic bag with the stripper and maybe some lacquer thinner, and sealing it, letting it sit for the better part of a week... then rinsing it off... <worried expression on face>

             _-_-WBear2GCR

PS. "...so when are you going to have it on the air?..."     Roll Eyes

      _-_-bear
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
The Slab Bacon
Member

Offline Offline

Posts: 3934



« Reply #7 on: December 16, 2006, 10:14:52 PM »

Bear,
        If you have to paint aluminum, there are several good primers out there. Some mfr's call them "self etching" and others call them "acid wash" but they are designed for aluminum and not real toxic. We paint architectural aluminum stuff at work all of the time. We get ours from Sherwin Williams chemical coatings division in Harrisburg Pa.. they will sell / ship to anyone. If you want, I can get you their fone numba when I go back to work on Monday.
                                                                 The Slab Bacon
Logged

"No is not an answer and failure is not an option!"
W2XR
Contributing
Member
*
Offline Offline

Posts: 890



« Reply #8 on: December 16, 2006, 10:59:32 PM »

Another technique for painting aluminum is to first remove all of the old finish by chemical or abrasive means (such as glassbeading, etc.), and then irridite the aluminum. This is a chemical film treatment; it is also referred to as alodining. It creates that gold finish that you see on aluminum components that are used in both military and best-grade industrial/commercial electronic equipment, such as the chassis in the 75A-4, etc..

Irriditing is ideal in that it not only inhibits oxidation of the aluminum, but it provides an ideal interface for the paint or primer to bond to the metal, and it is also electrically conductive.

Irriditing may be sourced by searching for "metal finishing" in your area. It is inexpensive and also provides an attractive appearance for aluminum parts that are not to be painted. Metal finishers typically charge on a lot basis, and the typical ham radio project (chassis, rack panels, etc.) should'nt run more that $25.00 to $50.00, depending upon the generosity of the guy doing the work.

All of the painted as well as unpainted aluminum components used within all of the homebrew creations here at W2XR are irridited. If the gold finish does not meet your appearance criteria, you can get the parts clear irridited instead.

Good luck with your project & 73,

Bruce
Logged

Real transmitters are homebrewed with a ratchet wrench, and you have to stand up to tune them!

Arthur C. Clarke's Third Law: "Any sufficiently advanced technology is indistinguishable from magic".
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #9 on: December 17, 2006, 10:31:23 AM »

Bacon, thanks for the lead! I can contact Sherwin Williams... btw, how does it work in a spray gun that has an aluminum cup??   Roll Eyes

Bruce, XR, glassbeading leaves a slightly pebbled surface usually. That means some sort of primer/filler & sanding. I'd like to avoid that if I can.

Looking for a whiz-bang chemical stripper to do the job.
The ones I've tried in the last few years have been very poor compared to the toxic sludge that they used to sell... and suggestions out there for one that actually works on real paint would be appreciated.

I know about Alodine and "Irridite" - afaik these are both "chromate conversion" methods, or similar. I actually have some Alodine here, but won't use it since it contains Hydroflouric Acid in the prep bath and I do not have full rubber suits and face masks available.  Cry

The panels are already "gold finished" under the paint. I just would like to get the old paint off, and not paint over the not so good paint...

There are three panels, each 3 ft wide and a foot high.

I may call up some finishing houses in Mass (none in NY, ya know...) and see if they will take the paint off when then dunk the panels as part of the deal... but in that case I may just ask for them back, do some fancy dan "graining" and have them done up in grey anodize... but that may not actually look as good as the paint... and will cost more.

       _-_-WBear2GCR
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
W2XR
Contributing
Member
*
Offline Offline

Posts: 890



« Reply #10 on: December 17, 2006, 12:15:34 PM »

Bear,

If the media used for glassbeading is correct for the desired finish, there will not be any issue with "pebbleing" of the finish. Note that I'm specifying glassbeading, and not sandblasting here. I have parts glassbeaded all the time for electronic equipment restoration, auto parts for a car I restored, etc. It has been used widely for years for the restoration of classic autos that are concours d'elegance quality, and the guys in that field never would tolerate a surface that is anything less than ideal. Yes, they do use surface filling primers, etc., but again, if the media is correct, you will not need to use anything other than a normal primer for this refinishing exercise.

It's a heck of a lot more environmentally-friendly than the harsh paint stripping chemicals that are out there, it's qucik, and it does the job.

BTW, there is a company out there called Redi-Strip that does specialize in the chemical removal of paint, rust, etc. I used them to strip a steel Ampex 300 console I restored a few years ago; I drove to Allentown, PA from Long Island to get this done. All of the paint was gone, but the steel started to corrode by the time (a few days later) I picked the unit up. It turned out I had to get the unit glassbeaded after that anyway to remove the light surface rust that developed, and the finsih was perfect after the galssbeading; ready for paint with no need for any special surface primer, etc. It was painted the correct smooth finish that Ampex originally used, with absolutely no orange peel or pebbleing in the finish whatsoever.

I say glassbead it and you'll be happy! A good glassbeading guy will know exactly what grade of media to use for your application. #220 grit is probably a good starting point, but I'll defer to the experts. After the glassbeading, you may still want to have the parts irridited for the reasons I provided earlier.

73,

Bruce

Logged

Real transmitters are homebrewed with a ratchet wrench, and you have to stand up to tune them!

Arthur C. Clarke's Third Law: "Any sufficiently advanced technology is indistinguishable from magic".
W2XR
Contributing
Member
*
Offline Offline

Posts: 890



« Reply #11 on: December 17, 2006, 12:31:54 PM »

Bear,

Further to the refinsihing of these panels;

Irriditng is essentially a non-toxic process and I've been to the metal finshing shop here on Long Island numerous times and there is no hydroflouric acid used in the process. You can dunk you hands in any of the chemical baths used in the process all day long with no ill effects. They used to say the same thing about PCBs, so I don't want to got too far here............!!!!

If you do grain the panels and anodize them, bear in mind that anodizing is not electrically conductive; it is really a dye that is applied to the aluminum. If the panels are required to provide electrical shielding or a ground return, etc. you are asking for trouble here. On the other hand, irriditing is electrically conductive.

The process for graining of panels is done by a machine called a Time-Saver. Any good machine shop that works with  sheetmetal will have a Time-Saver available. The belt used for graining panels for high-end audio gear front panels, etc., is a 180 grit belt. This grade belt can also be used for prepping the material prior to paint; it will not leave any grain in the painted finish and it can also be used for removing the old finsih from rack panels if desired, so that is another alternative for paint removal for you. I just had a couple of rack panels stripped of old paint using this process, but you still have to manually remove the paint from the edges and notches of the panel, as the Time-Saver belt cannot reach these areas.

When I restored the stainless steel facings on my Ampex recorders, I had all of the facings regrained on the Time-Saver with a new 180 grit belt, and they look like they just came from the factory in Redwood City 50 years ago!

Good luck with the T-368!!!

Bruce
Logged

Real transmitters are homebrewed with a ratchet wrench, and you have to stand up to tune them!

Arthur C. Clarke's Third Law: "Any sufficiently advanced technology is indistinguishable from magic".
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #12 on: December 18, 2006, 03:09:06 PM »

Bruce XR,

Thanks for the encouragement on all this.

Turns out only the RF deck has an aluminum panel, the rest are steel - which is somewhat simpler to deal with...

Iridite is a toxic process. I'm not getting near it! 

The main ingreedient is Hexavalent Chromium. The activation baths contain:
acetate; formate; sulfate; chloride; flouride; nitrate; phosphate and sulfamate ions. This is according to the Metal Finishing Guidebook, and the article is written by someone from McDermid, Inc., the people who own the "Iridite" name.

I'm quite aware of anodizing and its lack of conductivity. Lockwashers usually suffice to make a decent contact, or else the removal of some material in contact areas will do the trick.

As far as the Time Saver is concerned, I'm not so sure that the thing has the right name or where that name came from!  Wink  The problem with the Time Saver is that it will take the leading and trailing edge in the direction of travel of the belt and round it off, unless you pack it in with a leading and trailing piece flush to the surface of the one you want to "grain." If there are holes, you have the same problem.  I prefer the "Stroke Sander" by far for doing "graining" since it is under operator control and permits you to avoid some of these problems.

The other useful method is to use a "Scotchbright" wheel of appropriate type to do the graining. The stainless steel sink industry uses them extensively... they come in all sorts of grits and types...

 Grin

I was just reading that blasting with wheat starch (!) and sodium barcarbonate are very good for removing paint without harming the metal at all! Also plastic media is mentioned in the same application - over even fine glass beading, fyi. The plastic media is mentioned for stripping paint from aircraft and fiberglass!
 Cool

               _-_-bear
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.076 seconds with 18 queries.