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T368 power output




 
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Fred k2dx
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« Reply #25 on: January 20, 2010, 05:34:02 PM »

http://www.amwindow.org/tech/htm/t368aud.htm
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WBear2GCR
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« Reply #26 on: January 20, 2010, 05:34:14 PM »

I have a bc610 mod transformer but its the end bell type, like the power trans I have.
Maybe these were from early bc610 units?
Didn't they make different models?

Brett

"E" BC-610s started to use the potted transformers.
It's the "deco" styled ones (I like that look!) that had the end bell un-potted iron, afaik.
The T-368 takes a lot of heritage from the later 610s, imo, since the iron looks rather similar in size and shape.
My T-368 power deck has the "A" or first version power iron which like some of the later 610 iron has a 220vac primary option there... of course the rest of the iron does not seem to have this available, making running it from a 220 line problematic... dunno if this was just a last run 610 power iron thrown in or not??

                _-_-bear


EDIT: I think I have decided I will be making my T-368 available - can deliver to NearFeast - inquire via PM or email, yes I will post to the FS section...

Btw, you may think you have a "C" model, because of the badge, but many were "reconstituted" from various versions, each deck being somewhat random. Mine has a later RF deck (I think) with the engraved panel... aluminum, the other two are steel stamped panels.

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ke7trp
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« Reply #27 on: January 20, 2010, 08:12:18 PM »

Mine is a C.  All decks match.  Tube layout matches. Not sure if thats good or bad.. But its a C.

Ok.. More work today.  Pull RF Deck out. Very simple.  Carried it to the work bench. Fan is SHOT.  Turning it by hand, the bearings are very stiff and noisy. 

I have a new dayton ball bearing fan that might fit. But the old has 4 wires and the dayton has 2.  I am going to have to figure out what the others are for.

The 4-400 looks real shot.  I am going to put a new Eimac I got from Robert in there. Clean up the Deck and check the exciter tubes.

On the home stretch.

C
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WBear2GCR
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« Reply #28 on: January 20, 2010, 08:19:48 PM »


Don't go by looks on the 4-400, might be shot, might not. See how it works?

The fan bearings are known to go. They can be replaced. Some folks have retrofitted quieter fans, but be careful about putting in fans of insufficient CFM and back pressure capability...

I'd take the fan out, lube the bearings with synthetic oil and see how it flies - old oil gums up.
It might make sense to dose the bearings with a hypodermic with solvent to un-goo the old petroleum in there. Dunno if they are sealed or not, likely sealed, but sealed may be penetrated by solvent.

The squirrel cage comes off (soak over time with penetrant on the screws and down the shaft before attempting removal, imo), then it is a motor. Dissasemble as required to get to the bearings. Any pro bearing house can remove, and replace.

                      _-_-

PS. there is a T-368 (I think the BC610 groups is part of it too...) group on Yahoo Groups, with some experience with the fan and other issues... fwiw.

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ke7trp
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« Reply #29 on: January 20, 2010, 09:27:54 PM »

The bearings are sealed.  Cant be cleaned. They are toast. Super rough and worn. They stock them down the street at the bearing house.  I am going to clean it up and replace them.  Then I am going to put a rubber isolation gasket on like this Dayton has. I hope this will be enough to silence the thing. 

Might tear it apart tonight. 

There is a burn spot on the 4-400. I have a new one. I am going to put it in. This one will go as a spare.

I still dont see how to hook the audio up.  The links that where sent to me are major overhaul of the speach amp. I dont want to hack this thing up.  I just want to add the outboard audio.

C
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WBear2GCR
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« Reply #30 on: January 20, 2010, 10:34:34 PM »


I dunno the schematic, but it seems to be a rear panel J<something> connection to drop in a 600ohm line level source...

If the 4-400 still functions - the old one - use it for tuning up the first few times, and make sure it is stable first?

yeah replace the bearings... look at the yahoo site, they have discussed the fan I am pretty sure... there was a concensus about what to do, iirc.

then let us know? Wink

           
                       
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ke7trp
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« Reply #31 on: January 20, 2010, 11:28:02 PM »

Thanks.. I have had the rig up and running.  The 4-400 puts out from 400 to 600 watts carrier depending on where you load it. It has great output. Peak is low and audio is still low. 

I will look up the yahoo group and do some research. The fan is now out. 

C
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flintstone mop
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« Reply #32 on: January 21, 2010, 11:53:13 AM »

Clark,
If you can go over the T-3 and see if certain mods have been done to the RF final tank circuit and speech amp, there should be steller performance and a lot of modulation with the stock tubes and transformers. The famous Timtron mods.
No need to go to 220.
And the power output should be tuned for 250 watts. Then the TX is on easy street to make nice clean audio.
That's not a 500 watt output transmitter. 300 watts out is the spec.
Not good to run things to beyond max.

I don't like what I see in your mod scope. The bottom pic.
Fred

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Fred KC4MOP
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« Reply #33 on: January 21, 2010, 12:46:31 PM »

The specified current and voltage will dictate power out. 

I understand you suggesting I load it lower then the manual says.  I am doing that and this helps to make room for audio. thanks.

I guess you missed the rest of the post. I have since fixed the mod. I am now at peaks with no flat topping and 80%. 

My trouble was with the screen regulator tubes. After that was fixed, The rig came to life.  I guess I will never know how one of these works with all the speech amp mods.  I am not going to hack this radio up. Its 100% stock and restored. 

I will try to get pictures of the Scope after the screen was fixed so you guys can see it.  I am just real busy right now. I have to fight the storms and snow on a bussiness trip Sad


THanks again for all the help!
Clark

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K5UJ
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« Reply #34 on: January 21, 2010, 01:04:28 PM »


And the power output should be tuned for 250 watts. Then the TX is on easy street to make nice clean audio.
That's not a 500 watt output transmitter. 300 watts out is the spec.

Fred,  is this true?  I had somehow been led to believe the T368 was a much bigger maul.  Loafing all day at 500 w. and capable of 700.   A real full gallon of days gone by.  I wish I could remember where I read that but I think it was in more than one place. 

Rob
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k4kyv
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« Reply #35 on: January 21, 2010, 02:30:59 PM »

I would look at whatever the army manual recommends for power output on phone, load it to that power level,  and modulate to 100% or to whatever level is achievable just before distortion sets in.

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w3jn
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« Reply #36 on: January 21, 2010, 03:20:19 PM »

Clark, besides throwing that iffy OA2 over the shoulder, what did you fix to get the thing to 100% modulation?

On mine, I had to run a hefty extension cord into the laundry area which is closer to the breaker panel.   Altough the 110 outlets are on a 20 amp circuit in the radio area, there was considerable voltage sag on xmit.  I could watch the fil voltage sag about .2V on xmit, even more on mod peaks.
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W2XR
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« Reply #37 on: January 21, 2010, 03:27:26 PM »

Mine is a C.  All decks match.  Tube layout matches. Not sure if thats good or bad.. But its a C.

Ok.. More work today.  Pull RF Deck out. Very simple.  Carried it to the work bench. Fan is SHOT.  Turning it by hand, the bearings are very stiff and noisy. 

I have a new dayton ball bearing fan that might fit. But the old has 4 wires and the dayton has 2.  I am going to have to figure out what the others are for.

The 4-400 looks real shot.  I am going to put a new Eimac I got from Robert in there. Clean up the Deck and check the exciter tubes.

On the home stretch.

C

Clark,

Possibly for connection to a motor running capacitor?

The blower on the RF deck of my GPT-750 uses an external running cap, so perhaps yours does too.

73,

Bruce
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flintstone mop
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« Reply #38 on: January 21, 2010, 04:02:26 PM »


And the power output should be tuned for 250 watts. Then the TX is on easy street to make nice clean audio.
That's not a 500 watt output transmitter. 300 watts out is the spec.

Fred,  is this true?  I had somehow been led to believe the T368 was a much bigger maul.  Loafing all day at 500 w. and capable of 700.   A real full gallon of days gone by.  I wish I could remember where I read that but I think it was in more than one place. 

Rob

Hi Rob I stand slightly corrected. Look like it will do 400-450 watts out. I always loaded mine for 300 watts or near 250 watts to let the modulator make lottsa audio.

And the modifications did not hack anything at all. They were slight component changes on the RF deck to allow more high audio freqs through and stop the arcing in the final (an additonal component called a DC blocking capacitor). The speech amp mods allowed more low end and audio drive to the modulators. That's it. The T-3 was a workhorse for RTTY not A.M. There were on-pupose engineering shortcomings for A.M. use that limited the modulation capabilities of the T368. To prevent the bozo factor from unskilled techs in the field.

Fred
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Fred KC4MOP
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« Reply #39 on: January 21, 2010, 05:29:08 PM »

Wow.. Thanks for all the help guys.

First off we have two issues going on.

1. How to repair the unit because I think we all agree that it is broken.



Clark,

Do you have a REAL Oscope, not a station monitor or something that only picks up at the RF stage?

And a probe?

Take a gander at the input to the modulation transformer, and see if your clipping there.  Then work your way back.

Simple to find where it's clipping at.

--Shane
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N2DTS
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« Reply #40 on: January 21, 2010, 06:57:56 PM »

In this case, it might be different, but it seems some of the fun has gone out of things when radios are collecters items and don't allow one to change and modify (improve) radios, and have fun in the process.
There is not one 'ham' or military transmitter I would be happy with in stock form.

Something as big and heavy as a T368 should do 500 watts carrier and well over 100% modulation in my book.

True, some guys hack things up, but others do mods that look better then the stock setup was.

This is a modified DX-100...
http://www.classeradio.com/easy_h_2.jpg

Brett



And the power output should be tuned for 250 watts. Then the TX is on easy street to make nice clean audio.
That's not a 500 watt output transmitter. 300 watts out is the spec.

Fred,  is this true?  I had somehow been led to believe the T368 was a much bigger maul.  Loafing all day at 500 w. and capable of 700.   A real full gallon of days gone by.  I wish I could remember where I read that but I think it was in more than one place. 

Rob
[/quote]

Hi Rob I stand slightly corrected. Look like it will do 400-450 watts out. I always loaded mine for 300 watts or near 250 watts to let the modulator make lottsa audio.

And the modifications did not hack anything at all. They were slight component changes on the RF deck to allow more high audio freqs through and stop the arcing in the final (an additonal component called a DC blocking capacitor). The speech amp mods allowed more low end and audio drive to the modulators. That's it. The T-3 was a workhorse for RTTY not A.M. There were on-pupose engineering shortcomings for A.M. use that limited the modulation capabilities of the T368. To prevent the bozo factor from unskilled techs in the field.

Fred
[/quote]
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K5UJ
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« Reply #41 on: January 21, 2010, 07:07:52 PM »


Hi Rob I stand slightly corrected. Look like it will do 400-450 watts out. I always loaded mine for 300 watts or near 250 watts to let the modulator make lottsa audio.

Okay Fred gotcha; I was thinking with the tubes in the RF and modulator (which sounded like a KW1 tube compliment) it would do more but I understand the mil. design angle now.  Well, 400 w. certainly ain't shabby at all.  Anyway, as Derb once wrote, it's the antenna that makes ya a strapper.

Rob
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w3jn
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« Reply #42 on: January 21, 2010, 11:36:36 PM »

The T-368 is roughly half a KW-1, Desk KW, or GPT-750, all of which used the same toob complement (pair 4-250s mudulated by 810s).  Either is good for about 750W carrier out fully mudulated, or a KW CW.
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N3DRB The Derb
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« Reply #43 on: January 22, 2010, 02:55:46 AM »

clark dont wanna make any mods as the rig was belonging to a elmer of his. wants to keep it like he had it.
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K1HH
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« Reply #44 on: January 22, 2010, 08:25:32 AM »

Clark:

I looked in my T3 manual, and here are the input pin numbers for J12 on the rear of the unit.

Pin D is the 600 ohm input
Pin E is ground
Pin F is carbon mic/13v input

The book also shows a maximum of 350 ma plate current for CW but only 275 for AM, and some online sources suggest 250 ma for best audio. Mod bias should be set for 50 ma idle current, with peaks to 230 ma to not exceed 100 percent modulation.

Cleaner modulation can be had easily by turning the clipper control R44 CCW on the speech amp.

If you don't have a manual they can be downloaded on the internet.

The operators manual is TM 11-809-10
The field and depot maintenace manual is TM 11-809-35.

Rodger
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ke7trp
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« Reply #45 on: January 22, 2010, 11:21:39 AM »

At 275 Mils this is 500 watts of AM carrier rock solid.  Even down at 200 Mills, Its still 400.  I cant load this thing down lower.

The thing is being powered of a dedicated 30 amp line with number 8 cable and a 30 amp connector.  126 volts at the wall. 1 to 1.5 volt sag under load.

I got 80% mod now at 400 watts carrier after replacing tubes.

I am going to change the DC blocking caps and door knobs as they are easy to do and that will really help the audio. 

I am going to run the outboard audio into the back and try that.

My Clipper is now bypassed with a wire.

The speach filters are bypassed now.

The fan is out being rebuilt. It was toast.  When it comes back, I will try it all again. 

Baby steps.  Its at 400 watts carrier and 1400 pep now.

C
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« Reply #46 on: January 22, 2010, 04:22:25 PM »

There is another jack marked J13 on the rear of my T3. It connects in the AC primary line to the input of the HV transformer. When I got mine there was a jumper wire across the two connectors, simulating a plug. I removed the jumper and bought the plug, but in reading the manual there is a very brief note about using this for external power control. Another friend who has a T3 said he had put a Variac in this spot and it becomes an "adjust-a-watt" control. I have done the same, and its an easy way to back the power down.  I suffer from high line voltage here. Another of my T3 friends had a 30 amp variac across the input line to his transmitter.

Rodger
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« Reply #47 on: January 22, 2010, 04:31:33 PM »

Great tip.. Mine has a plug in Jumper in that spot right now.   Thanks alot!

Clark
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« Reply #48 on: January 30, 2010, 01:22:33 AM »

Just an update guys.   

Got the Blower motor rebuilt by A1 electric in PHX AZ.  They rewound it, Machined it, Put new sealed bearings in, balanced it and even painted it the original color!  It looks like new!

I installed it today with a Foam rubber gasket from the motor to the deck.  The original gasket was missing so I made one. The motor is near silent now.  I am sitting 3 feet from it as I type this and can hardly hear the thing.  Air is blowing out the back at a high rate.  They did a great job.

I also put in two matched Eimac 4-125s.  Burned them in for 4 hours. A New 4-400 and with the Screen tubes replaced, I have full power. I can full modulated a 550 watt carrier when tuned by the book.  I have 100% mod on the scope and the signal is clean and clear.  I backed the load down to lower the carrier and it does right at full legal limit. 

Now to hook up the External audio and this beast is done.  I will post some pictures of it soon.

Clark
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