T368 down need a part

[ke7trp]

Thats a great idea also!

C

[AC0TX]

Google: McMaster Carr

Complete catalog on-line

See   High-Precision Bellows Shaft Couplings

BINGO!!

They accept small orders from small people

To get their catalog is impossible as you need a machine shop and a salesman might come to drop it off
other possibility is Ebay  but online catalog is very good

AC0TX

[k4kyv]

And they ship the same business day or the next.  I can place an order on-line over the weekend, and if they have the merchandise in stock, it usually arrives here by the following Tuesday.  They are not cheap, but they have stuff I haven't been able to find elsewhere locally or on line, and they don't require a minimum order. Their on-line catalogue is great. I wouldn't want the paper catalogue (didn't even know they had one); to contain all the info you can get on  line, it would have to be about  8" thick and would likely go out of date very quickly.

[ke7trp]

Thanks for the tip but not a single part they list will work.  The coupler is 1.25 inchs over all length,  1/4 on one side and 1/2 on the other.   They do make a 2 inch version but there simply is not 2 inches in the T3 without making or machining a ring mount to space the big capacitor back 3/4 of an inch.  I suppose, I could rig something up with standoffs as a last resort.  The problem there is you get the HOT side of that cap closer and closer to the chassis wall.  It would be just my luck to have that arc out.

I have not had good luck with rubber hose. 1.25 and that large diam diference is too great.  I messed with it for hours. 

The Fair radio part came in the mail today.  Woops.. one side is 1/4 and the other 1/4.  No room to bore it out.  Guess it goes into parts stock.

My rescue this time around was w0vmc.  He was nice enough to take this part out of his personal unrestored T368 and send it to me.  What a hell of a guy.  I am still looking for replacements. THe website which stocks the part I need will not email me back and nobody returns calls.  I am sure this part exists and when I find it, I will order spares for Roberts rig and mine. I am sure other T3 owners might want one each as a spare.

For now, I think I will have the rig up and running next week!  I cleaned up the deck, Put in some new 4-125 eimacs, got some SS plug in for the screen voltage supply for the Modulators (hoping for a tad more audio power) and checked all the speach amp tubes.  Cant wait to get the ole Girl back on the air. I was enjoying myself kicking back in the big high back chair, Feet up and a D104 in my hand.

C

Google: McMaster Carr

Complete catalog on-line

See   High-Precision Bellows Shaft Couplings

BINGO!!

They accept small orders from small people

To get their catalog is impossible as you need a machine shop and a salesman might come to drop it off
other possibility is Ebay  but online catalog is very good

AC0TX

[Tom W2ILA]

I broke mine last weekend.  Problem solved within an hour:
Loosen the good coupling (loading or tuning) so that it can also slip free.
Unfasten the 4 screws holding the tune/load counters in place and back the panel out slightly.  Do not loose the backing plate that secures the 2 inboard screws.
Remove the halves of broken copper bellows from the counter and cap.
Go to kitchen and find vinegar - put enough in a dish to cover immersed broken copper ends.
You need this step to help clean the copper in prep for soldering.
Soak the coupling for at least 10 minutes in vinegar.  Then thoroughly rinse the bellows and finally dry with compressed air. Other cleaning methods are encouraged.
On the bench match up the broken bits and secure them lightly by pinching the broken copper sections.  Secure the assembly in a small clamp.
Using a big soldering iron flow solder between the broken bellows.  Use plenty of heat.  Keep solder away from all other sections of the bellows.
You should now have a cleanly soldered, repaired, squeaky clean bellows assembly.
Re-assemble via reverse of removal procedure.
Calibrate both by backing the counters to zero and turning the caps to match (this step will assure you that the tuning graphs in the book are in agreement).
This repair method has lasted 10+ years on the loading cap.  Hopefully the tuning cap coupling repaired last week will last as long.
73
Tom

[ke7trp]

Mine was torn apart and twisted. Not repairable.  Someone had hammy ham boned both couplers already over the years by doing just what you said.  Solder.  The loading one had four seperate slober jobs.  The right one had two spots.

This job for me is complicated because I cant pull the Plate with the turns counters out like you did.  Boy would that make life easy..  My T3 was restored and repainted the painter did not remove the two sections so the joint is smooth with paint. i would have to try to cut it wout a blade and then you would be able to see it. I had to remove the cap and slide it back instead.

I realy like fixing things the proper way and it really bothers me to rig things. Its just my nature I guess.
C

[Tom W2ILA]

WOW, I didnt realize I was such a hammy hambone!  I almost feel bad I posted such a horrid repair suggestion.
I hope the community can find some correct replacements to keep these rigs going.
73

[flintstone mop]

no Tom
Do not worry about that. IF you can flow solder correctly, it would not be Hammy Hambone. I'm sure Clark's repair was not a good solder job OR someone went past the stop and twisted the living hell out of the tuning knob. That would fold up the entire bellows.
Fred

[Ott]

no Tom
Do not worry about that. IF you can flow solder correctly, it would not be Hammy Hambone. I'm sure Clark's repair was not a good solder job OR someone went past the stop and twisted the living hell out of the tuning knob. That would fold up the entire bellows.
Fred

I looked again at the ones in my T-3 and they do appear flimsy...

I'm just guessing but... perhaps they were built mechanically weak so as to be sacrificed during that very event you mention rather than possibly damaging the vacuum variables?  That is, they are a consumable by design?

[ke7trp]

Tom. I did not mean to insult you. That came out wrong.  I am sorry. 

I just do not like to rig things back together.  When you use Solder, that bellow can no longer flex.  The factory parts lasted for years but it seems this is a sore spot for T3s

C

[Opcom]

WOW, I didnt realize I was such a hammy hambone!  I almost feel bad I posted such a horrid repair suggestion.
I hope the community can find some correct replacements to keep these rigs going.
73

Me too. I was thinking about solder. I better stop doing that.

[The Slab Bacon]

Here is a thought  

I usually look for a mechanical solution that is better than the original (stronger in this case) Beings that I am a half-assed machinist I won't hesitate to machine something up to do the job.

How about taking a universal joint from a 1/4" drive socket set, bore the female end to take a 1/4" (or whatever) shaft and then drilling and tapping it for a setscrew. Then take a 12 point socket close in size to the larger shaft then bore (or drill) it out to fit the larger shaft and drill and tap it for a setscrew as well. Snap the 2 together and fit it in place of the original bellows coupler. It would be many times stronger than the original, and none of us would live long enough to wear it out and it would allow for the slight misalignment of the shafts.

If overall length is an issue, maybe try it with a swivel socket instead.

I have used socket set universal joints in the past for other similar applications where speed is not an issue. They are reasonably cheap and readily available.

Just another $.02 worth...........

[KC9LKE]

Clark:

Well I guess I got to chime in also.

Seems like this is somewhat common in the T-368. I have a couple vac variables with a 1/2” collar and “leftover” copper material.

A bellows coupling is intended to couple two shafts together without adding backlash that’s it’s advantage over a “Love-joy” type coupler.  However you may not be concerned about the backlash from a spider type coupling in this application.

My concern; if I am looking at your pictures correctly the two shafts are way out of alignment.  If you look over a spec-sheet for a bellows type coupling you will notice that they do not tolerate shaft misalignment like a spider type coupling will. The “why it broke in the first place”.  Also the lateral force on the vacuum variables lead screw is not the best thing for longevity either. The aluminum “cup” on the capacitor floats, so lateral force is taken by the plug or “nut” in the capacitor causing premature wear.

Look around for a replacement and if at all possible try to correct the misalignment as much as you can or you may be through this again.

JMHO.

Best regards
Ted / KC9LKE

[ke7trp]

Thanks for the tip on the alignment. I have the replacement on the desk here from robert. I am going to install it tomorrow.  I will try my best to align everything.  I am eager to get the ole girl back up and running on 15 meters.  I have been using the yaecomwood with about 25 watts and I am currently having "transmittter envy" when I hear a big signal come on

F, I dont think a Universal would work here. We only have 1.25 inches.  Thats a great idea though.

C

[ke7trp]

Update,

I got the bellows coupling in from w0vmc.  It was in great shape. No slobber jobs on it.  I ended up using a blade and tracing around the panel through the paint. Then loosening the turns counter unit and sliding it out. If you remember to loosen the tuning bellows this is an easy job. 

I had some trouble getting the turns counter lined up with the correct capactance for full load. I just kept sliding the drawer out and then loosening the bellows, cranking the crank, then tightening the bellows.  With in a few minutes, I had it back in line at 250 MA on the plate and readings that where very close to my old chart. 

While I was there, I replaced the 5R4's with Solid state plug ins from Ebay.  These are $5 each. The T3 finaly reaches 100 % mod now. The old readings on the power master NIST meter where 1280 before flat topping (watching O scope) with 5R4s.  Now, I get 1480 with SS plug ins. This is great as I dont want to run over legal limit. Carrier is about 405 loaded down and about 500 loading by the book.  The peak output modulated power stays the same at 1480 either way.  Can you tell on the air?  Maybe not.  But having all those 5R4s out makes the room that much cooler and we are going into summer here in AZ. 

I am glad to have the T3 back up and running and will put the rig on the air tonight on 75 meters.  I tried and tried and the T3 just will not make it to 15 meters.  The books limit says 20mhz and I think that is right.  The Exciter will go right to 15 but the transmitter will not.  I have heard of people running T3s up there but they must have moved the High band tap over a bit on the coil. 

C

[Fred k2dx]

Mine tunes up fine on 15m with no changes needed. Power out is not as good as on the lower bands but I think it was around 400 watts. I use a HP function generator as a signal source. 

Only on 15m it seems there isn't much T/R isolation in the antenna vacuum relay though... my Harris RF 590 receiver shows a RF overload warning and has a fit.

[ke7trp]

Interesting.  I think it might be the range of the tuning cap.  I ran out of range.  I guess I could unscrew the bellows and turn the crank a bit to get me more range. I bet then it might go. 

C

[Dave KA2J]

I'm glad you got the T-3 back on the air Clark.  Interesting discussion.  I'm hoping my A model keeps plugging along, as it sure seems to be bullet proof since I've put it on the air years ago.  It's a wonderful transmitter.

Hi Fred.  Hey!  I'm Reddy Kilowatt

Good luck Clark and I'll look for you on 80M soon, T-3 to T-3.

Dave KA2J