The AM Forum

Got the T368 today.  Took some crapy pictures as I forgot the camera on the way out the door.  This unit belonged to my Friend WD7I. He lost his battle with cancer recently. WD7I got the unit from W8QBG who rebuilt it.

So far so good.. I made the "mating cable" up for PTT and mute.  It makes full Power.  The Blower is so loud I cant hear myself think.  It has to be bad.  I am going to look into that this week.  Here are the pictures.

Clark

More pictures.

Now you just need to locate some 6000s and you will be set for life.

What a beast!
I have heard some that sounded very good.

Do you really need a blower?
They are built like tanks, if you don't strap the tubes, I am sure all you need is some gentle air flow...

Brett

4-400 needs good air flow through the socket. check out Eimac spec.
blower bearings need changing

Yep.. Got some work to do:

1. Rebuild blower or replace.  I have two Big Dayton units. Maybe one will fit.  Variac the blower to kill some RPM off.  Ham use at lower power does not need this much fan.

2. Figure out how to hook the audio rack to the 600 ohm balanced input.. I tried without any luck.

3. Bypass Clipper and Speech filter.

Thats about it. Its a clean stock restored T3 and it needs little.

Clark

The 30K1 used a 4-125 in the final with no blower/fan.
I put a 4-400 in without air, never had a problem, running over what I did the 4-125.

The globe king 500 used a 4-400 (or was it a 250? ) with just a wimpy little fan.

Brett

Yeah.. When I get into the thing, I will know what blower to use. I cant stand this noise. Its as loud as a Vacuum cleaner in the room.  I think my Oreck might make less noise.

Its a single 4-400. This thing was made to do Telatype 24/7 at full power. As a ham, I need half the airflow and none of the noise.

I just made a contact on it.  Kc3ol in Kansas city.  Got a good report at full power. Used headphones into the Rxer so I could hear him.

The Modulator bias control is 3/4s to get the current I need.  This scares me a bit. I think the 4-125s might be about done. I need to find a set as a spare. The Bias Rises up a bit if you get long winded.  The plate and Exciter are ROCK solid where I set them.

The Freq is super stable. It never moved off 3.8500 then entire time it was on.  The Dial on the front reads 3.750 so its off. Need to calibrate the VFO dial. 

What a neat old Transmitter. With some minor work, I think I will have a Great sounding stout old Rig!

Clark

Clark you are lucky.  I'm envious.  I hope to own a T3 some day. 

You say it takes 600 ohm balanced audio?   Because this is an issue I assume you are working with High Z unbalanced stuff.  You could put the audio gear into an isolation transformer.    I think you can just put the hot on one side of the transformer primary, the other side to ground and the secondary winding goes to the balanced input on the rig.  Try a Jensen transformer.   They make the JT 10K61 1M which is excellent for your problem.   It is 10K ohm to 600 ohm and is designed to take the unbalanced high Z output of a tube circuit and drive a 600 ohm balanced input.   You also get the RF and ground loop isolation of a transformer.   details here:  http://www.jensen-transformers.com/ln_out.html  click on the model number to get the data sheet.

Rob

sorry to hear about your buddy Clark, but glad to see the rig made it to a safe place. I hope whatever I have makes it to people that care when i croak out.

this is all you will ever need to know about mods to that txer. Do this stuff.

http://www.w1ujr.net/wa1hl_mods.htm

and maybe not enough blower, but I got 2 of these.... one from the guy at the link and I found a twin at a fester last year, so I have a matched pair now.

paid 5 bucks for the hamfest one -  but I thought the price was reasonable for a new unit off the website.  both brand new in the box. 15 cfm each.

I'm going to use them for my 4-400's.  With the SK 406's  they'll be fine.  I may buy another 2 off the website to put in stock for future needs.

http://www.ecrater.com/product.php?pid=2622984

Hey Clark,

I heard you with KC3OL tonight.  The band was mega noisy from QRN and QRM but your T-3 broke through just fine.  Just thought you'd like to know, it sounded good.  You'll get it sounding even better I know.  Nice rig.

73 KX5JT John

Thanks alot for the report.   Poeple are saying the Carbon mic sounds fine and real clear.  My hand is killing me from Gripping that damn pistol Grip mic..

I got up early to get on AM.  The T3 is working fine. Somehow, The fan noise is much less this morning. Maybe a few hours of running and then a night of cooling off, Helped the fan. Its still way to much noise for this small room though.

Thanks for the linke about the blower motors. I dont plan to mod this one or hack it up.  Just trying to run my audio rack in, Bypass filters and clipper. Thats it.

Rob.  The audio rack is outputing balanced low level, low impedance.   The T3 is balanced low level, low impedance. I should not need any transformer.

What I cant figure out, is the proper wiring for the plug.

Clark

I bet that was a sweet moment, especially if you also were thinking of your friend who has passed.

Did you roll video or audio to record for your scrapbook ?

Last year I decided I was not using my T-368 often enough to warrant the floor space. I felt it really ought to be on the air with someone who would use it and had the technical creds to keep it going. 

1957 Crosley, model "C," with the rare curved-glass Marion meters all the way across. I set it up to use an external speech amp, pair of 807s  in a Bogen PA unit that I got from Derb's fix-it shoppe when he worked in Baltimore.

I'm happy to learn the T-3 has since been on the air from its new home. Haven't had a chance to work it, that will be a melancholy moment. Just like the feeling I had when I was shutting down the transmitter for the last time at my place.

http://www.youtube.com/watch?v=17le97Cj3Uc

Wow.. Mine is a BW "C" model with Brand new Marion Curved meters all across.  They look fantastic. 

Nice video! 

I did not record the moment. I did do something when I first fired it up though. I gave him a call over the air and waited a minute of silence.

Clark

I have Paul's T-3 ensconced at our lake house.  Although it goes on periodic rests, it does get a workout when we're up there  ;D

I need some 4-125s if someone has a set. These are flat.  Keep having to turn Bias up higher and higher on them.

Clark

My tubes are good.  I was led to believe that this transmitter would do ALOT more power then does.  I had a guy tell me that it does 2000 watts pep.  That made sense since the rig has a 500 watt carrier.  That is not the case.  When I hook up a Heathkit watt meter, It slams the needled over hard to 2000 watts.. But if you hold a tone, It settles around 1100. 


My Plate current is spot on, My Mod resting current and my Mod peak current are spot on.  The voltages are perfect and at the books ratings.

I bypassed the two filters.  Simple job. Did not even remove the Speech amp.  I also put a Paper clip in place of the clipper like suggested.  I now have more then enough audio. I think its best to load this rig down to 375 watts and let it Ride.  Loading it up at 500 just gets you more carrier and no more audio.

Next up is to service and slow down that damn loud blower motor.

Clark

Monitor the output air it should be warm, not hot. A cool tube lives a long life. I suggest you check Eimac specs rather than self appointed experts. The 4-400 wants air through the socket. The 4-125, I have never seen any air specs on it. Check care and feeding. 6.5 vs 15 amps of heater current.

Keyed unit into Big Bird dummy for 15 minutes.  Cool air out the back.  Its running the same power as the GLobe king peak. THe Globe uses a small fan and no chimny. I think its ok to cut it down. if I get long winded, I will turn it up.

Clark

Are the 4-125's running AB1 or AB2?
AB1 is about 330 watts. AB2 is 400.

AB1 should be good for almost 600 watts input.
You could likely just plug in some 4-250's or 4-400's.

Brett

Its about 350 watts of audio.  I can plug in 4-250s but the Fil trans runs hot. I should change it.  I am not going any farther with this rig. I got it for sentimental reasons.  I will use it once in a while. The dual 304TL by dual 4-400s will be my HIFI machine.

Clark

4-250s or 4-400 in modulator overloads the transformer. I sold a pile of transformers rated for the job but all out of them now. I must have sold 20 of them. They had dual 5 VCT 25 amp windings. Maybe somebody in the N.E. still has one of those black transformers kicking around. 4-125s do the job ok.

Oh brother, another smug T-368 owner.

hey, you. Quit disrupting & instigating. next thing I know you'll be smug about yer smugness. I'm gonna be fresh on the scene at Richmond, see?  ::)

Cool. Todd and I will have a table there, so if you want to sell something, bring it. We'll do the lunch thing after.

ho-k.  :D  getting ready to invade the ghetto. band should be coming back into shape about now - I'm working on JN's 75A-2's.

I think it is ok to be smug if run a T3. The only unsmug thing about it is they only run on 120 volts.

Not smug at all.. Its 700 lbs..  and the same peak power as the globe king :)  I just wanted it because my elmer restored it and my friend ran it until he lost his battle with cancer.  Thats not smug :)

C

LOL. Since some posters like to use dictionary.com or whatever, consider looking up troll. You guys are too easy.

All kidding aside, since you are new Clark, you wouldn't know this. But about 10-15 years ago there were tons of T-368s suddenly showing up on the bands, and the QSOs were as bad the Flex QSOs are now.

Oh, I thought being mil spec it would be over rated enough for the bigger tubes.

Not much signal increase between say 300 and 500 watts...

I still have some t368 parts from when fair radio used to sell them....
What is the mod trans spec's, I might have one of those also.

Brett

Its a cool old Transmitter.. I got it going Hi Fi now.  Enjoying it tonight. 

Brett, Let me know what you have.  I have since been in contact with alot of T3 owners. 

I am looking for the big allen bolts for the Drawers, I am missing 3 of them and my friends is missing 4. 

Clark

I have the pto/multiplier section, always thought about using it as a vfo exciter, had some rf deck tune and load parts, maybe the mod iron (20,300 ohms to 9100 ohms), made by freed, solder sealed.
I may have other parts I got at fair radio 30 years ago, but don't know if they were from a t368.


I also have a bc610 power transformer and mod transformer.

The 610 power trans is really big and heavy for its power....

Brett

Those are good parts Brett. 

I got great reports on the T3 tonight with the audio rack into it.  I think I am about done with it. I would like to find the Allen bolts for it. Then, it will go into the final resting spot and sit on 160.  I will take some better pictures of the thing soon. 

I would love to modify it, but I think this one needs to stay the way it is.  I am going to finish my Dream TX soon and that will be my main Rig. 

Thanks to ALL that have helped me with this thing.. I needed ALOT of help to get it going and everyong pitched in. I love this forum!

Clark

Brett,

keep me in mind if you ever want to depart with the parts.  :D

Got a t368?
I have no use for the mod transformer, the pto part I might use someday....
Not sure where the final tune stuff is, gears and so on...

Brett

If you think a BC610 transformer is nice , try two across a 240 volt line.

Derb,
I have the front plate that tunes the final, with turns counters and gears, and that mod transformer which I am not sure is from a T368 or not.

I will hold on the the pto, but have the multiplier sub chassis part, I don't know what I did with the rest of the exciter deck.

Anyone know what the mod trans spec's were for the T368?

Brett

 

I was looking at mine the other day.. Its someting like 9K and 21K 250 Watt max.  Mine has the clipper bypassed and the Speach filters bypassed. This got me about 200 to 16K.  I cant get more low end. To much capacity in the tank

C

Has the PA tank been reworked?   In its stock form B+ is fed at the junction of the PI and L coils.  Moving the plate block C, and reducing it to a more reasonable value, and feeding B+ traditionally will help reduce the C in the PA tank.  I'm pretty sure the mod is on here somewhere.

Thats a Timtron mod.  I am not that handy to get do that myself. I dont want to hack this rig up. Its a very nice restored Rig.  I just did minimal mods to it.   I am sure it would help. But most of the people cant here be below 200 anyways.

C

doesnt excess tank C effect the highs instead of the lows??

Not according to Timtron. He told me that to get the lows. The Tank has to be changed.  I dont know enough about it to tell you.

C

Brett. I think I need that Mod trans.. Mine is not acting right. Hold on to it while I test mine please.

C

The trans is 9100 to 20,300 ohms, 250 watts, 300 to 3500 Hz 1db.
A poor mod iron for hifi!

Not sure what it does at the -3db points.

I never heard of the RF tank components limiting the low end, I have a hard time buying that even if timtron said it.
I would not expect the mod trans to go down to 40 Hz, but it might do 150 Hz at -3 db, who knows.

I forget what I paid for it at fair radio 30 years ago.
Free if its picked up, $50.00 for shipping.
I usually get burnt on shipping, I just sent a receiver out and it was $60.00 to ship it one state away!

Brett

I DON'T think its nice, its way to big and heavy for the power it puts out.
All that cast iron end bell stuff just adds weight, the CVM5 was like that 'lets just bolt on another 50 pounds'...

The RCA iron i have has all the weight in the core, with very little extra in the brackets and so on.

I have a nice 1.75 KVA RCA that is about the same weight, maybe a little less, with twice the core of the bc610 one.

PIX below.
Anyone have any use for the thordarson trans in front?
Cryptic tag, T6735,  .54kva, volts primary 4m,  type output, 4000, 5700, 8000.

Brett

Look up the mod section T368 articles. the iron is better than that 300-3500 rating. Also look on W1UJRs website for much T368 info in one place.

I never swept mine but it sure doesn't sound that restricted. The clipper and filters were bypassed and a line level input added to the speech amplifier by the previous owner.

I received the rear panel multipin connector from William Perry Co. They are very prompt. They also still don't take credit cards and bill you! It's good to see trust these days!  

 

Either you misheard or Tron mispoke. There is excess shunt capacitance in the final output section. This kills the highs.

Read Tron's mods here.

http://www.amwindow.org/tech/htm/t368.htm

Yeah.. I read that wrong.  I dont have a problem in the high end.  Mine goes to 16K.  Sure it slopes off but that is fine. Its more then flat from 200 to 12K where I need it. 

Something is wrong.  I hooked up the scope. It wont close the carrier.   YEC in San Diego is going to send me some Used 4-125s to try. Maybe I have one that is toast. I hope its that simple.

C

I have a post in the FS section, fwiw...

              _-_-bear

these troublemakers!

The T-3 was my first A.M.TX. Steve was the instigator there. (1990 Fair Radio $700 and received on a shipping pallet) After the Timtron mods it was close to Bcast quality with the stock iron, stock tubes. It will do a fair amount of Pos peaks with the 4-125's no need to "upgrade" to 4-400's as modulators.
It's happier with a tune/loading for 250 watts out. NO ONE will ever notice that you're not legal limit or whatever.

The blower is another story. I replaced the bearings in mine and it wasn't any quieter.
I think Warren had his blower keyed to be off while receiving and on for TX. Are there two fans in the T-3? The blower (noise) for cabinet air and a separate one for the final?

FRED

YEah. Two fans. One in the RF deck and one in the bottom cabinet. The lower one is switched and not noisy.  The top one is shot.  The bearings are gone. If it is not quiet with the new bearings and rubber gasket, Then I will put the dayton in. I ran it on the bench and its very smooth.

Mine wont load lower then 350.  No combination will let me do that.   It wants to be up around 500.  I wish the thing had an adjustable Drive Control. The 6000 tube in mine must hot.

Thanks for all the help. 
C

GREAT!
I did the same thing and the top fan got quiet after bearing replacement.

Fred

Clark,

There's nothing like having your big rig near you for adjustements, observation, etc.  But if it's noisy, it's a drag.  If you don't want to move it far away, here's a few ideas to quiet it down:

First add an exit temperture sensor to sample the 4-400's air. Run it as is to get a baseline reading. Those units are on eBay for under $40.

Then do one of two things:  Put a Variac on the existing blower and slow it down. See what you can get away with and still maintain a reasonable exit temp.
  
OR the BEST idea is to take out the blower and put a 4" PVC flange on the back of the T-368. and duct the air in.  Get the flange at Home Depot or Ace hardware, etc. Then mount a squirrel cage blower on the other side of the wall or even outside the house. Run some 4" duct hose (preferably fiberglass with smooth insides) to the T-368 flange. This will be quiet and very effective! Blower intake air turbulance noise as well as motor noise is 70%+ of the racket. Exit air noise is quiet white noise and soothing - and barely noticable on the air. Listen to my 4X1 rig using this technique. It moves plenty of air for three tubes too.   You need a reasonably quiet room to be able to run any audio processing (esp compression) on AM.  Let us know what ya come up wid.

T

Here are the latest pictures of the T368.  Lots of work done here.  Its HiFi'd and sounding great. The Audio is plumbed into the J12 connector. I installed a remote PTT and mute harness also.  Above it is my SP600 JX14 Rxer that also has the Hifi modifications done. 

Clark

Looks nice.
The t368 is a better looking piece of gear for military stuff, most of which looked nasty.
An R390 would match up well....

Brett

Yeah. I have an R390 and R390A. I like the SP600.  I will need to get the R390 up and running to match the T3 better. Then use the 600 over on the big rig.

C

Clark,

you got it going on. That's a good lookin shack.  8)  What's the cats name, and have you made the gear kitty proof?

One of mine managed to chew the B+ wiring of one of JN's 75A-2's when it was on it's end sitting at the bench. I was highly mortified and embarrassed at this. The culprit was Phoebe, who likes to chew on plastic, rubber, soft drink bottles, toilet paper rolls, and (who knew) Collins rx wirez.

if that rx had been energized, she'd be dead and Glo would have been in tears.

make sure that kitty cant get his paw into anything hot.

I love the sepia tone provided by what I guess was a cell phone camera. Adds an old buzzard look to the whole thing. Very cool.

Yeah. It was my Palm phone.  I will take some better pictures. I forgot my good camera.

I am on 7293 now.  Waiting on the capacitors to arrive.  This thing is working just FB

C

Roger the Timtron info on the tank circuit.
The blocking capacitor will eliminate arcing in the plate tank ciruit. The DC+RF+modulation is a little too much.
The mod tansformer will go down to 80hz according to Timtron
He was even surprised! Typical military spec, though

Fred

Love the shack shot... way too neat and orderly for moi, could never manage that!

The cat is a great touch, but the thing that makes it for me is the photo of the Heathkit SB line rig on the wall! I mean, how cool is that? The juxtaposition in time is what makes it for me, the Glube Kling and the T-3 both predate it, and they are there live, while the "modern" Heath is a picture on the wall!

 ;D

                 _-_-bear

If you don't want remove the DC from the tank as in Fred's remarks you might want to to better insulate the tank coil from the chassis as shown... it's an electrically tight spot there at the end and it's my understanding that when (not if) the tank coil arcs you will most likely loose the plate current meter... even with the meter diode protected...