The AM Forum

Labeled "parametrics, Costa mesa CA"

TF4RX21YY part number stamped..  Also 600324

MAX WV 7000 volts
MAX ALT, 10,000FT

Intput 14,500 ohms.  Output 40 ohms.

Here are some pics of it!

THanks alot guys!  Any info would be just great.

Clark

No answers, but a few thoughts:

A 362.5:1 impedance step-down ratio? Sounds more like output (or possibly interstage) iron than mod iron. That's quite the ratio.

The 40-ohm secondary makes me think this might be output iron from a PA system. That's just a gut feeling, though, I have no facts to back that up.

With an output impedance that low, I doubt it was mod iron. Vacuum tube plate circuits have very high impedances, and most solid-state transmitters are pulse-width modulated (they also endeavor to get the output impedance as high as they can so things like solder blobs don't take on a huge electrical significance).

...for what that's worth.

It says audio output transformer and it looks like that is what it is.  Probably from a big audio distribution/PA amplifier.  If you had a couple of them, could use back to back for a modulator for a tube-type RF stage, but 40 ohms is very low Z for use in a modulator.  I don't know if there might be a possible application for modulating a solid state RF stage, otherwise....good trading stock for maybe getting a more suitable transformer.

73,  Jack, W9GT

You could use that transformer as is for a mod transformer by driving the 40 ohm side with a high powered solid state amplifier on the 70 volt tap. I would use a hysing reactor to keep DC off the transformer. You may have the makings of a very good AM rig here.  ;D

How much does that xformer weigh? If it's 40-50 pounds, it's good for at least 500 watts audio.

It was used in a BC610 for a while with good results.  I am going to put it between my 810s and 4-400s. Maybe I will get lucky and it will work.  Its heavy... Probably more like 30 to 40 lbs though.

Clark

Are these separate amplifiers?

Yes.. pair of 810s as the modulators.  Two 4-400s as the Finals.  The old transformer is shorted. This trans was used  in a pinch on a BC610.  It sounded fine. Might not be ideal but it did work. I figured I could use it while I searched for a better Transformer. I found a couple but I cant afford them right now.  I already have a wooden cut out on the Mod deck for the old transformer.. I guess its worth a shot right?

Clark

I just don't know how that would work? How many ohms do you read on that so called 40 ohm tap?

This transformer was just identified.  It was used in an Airborn transmitter. THis transmitter used 4cx300Ys on the modulator. The person did not remember the model of the transmitter. Maybe someone else will.

It was used in a BC610 and ran fine for a year or so.  It seemed to handle the voltage just fine as we are at 1000FT:)

I guess its worth a shot.. The Ratio is wide.. but what the heck.. Its a 30 minute job to install it and another 30 minutes to set the rig up for testing.  I will load up the 4-400s at lower voltage and then add some drive from the 810s in.. I might get lucky

Clark

If it did work as a modulation transformer in a BC-610 then no way is the secondary impedance 40 ohms.

It might be good to feed a low 60hz voltage from a filament transformer into the primary and measure the voltage of the secondary. From that you can compute the turns ratio.

The square root of the of the primary to secondary impedance equals the primary to secondary turns ratio.

Interesting.  But I found that it came out of a Transmitter with Two 4cx300Y tubes. I am trying to get the full information now but the part number jives. It is a modulation transformer. They used a choke or a Reactor on it though. Even the mounting is correct.

Eitherway.. It worked well in the BC610 and sounded fine. I better not try it.. If I do and it works you guys will never beleive me :)

Clark

Did you ever hear that BC-610? Even with a choke, it would not have worked in a conventional circuit. As far as not to believe you, I say damn  the torpedoes, full steam ahead! Often times in the past I was told somethings would not work, sometimes they were right, sometimes they were wrong. This is how we learn. So if it doesn't work, you learned something. If it does work, we'll scratch our heads and wonder why.   I just wish I had a transformer like that to mod a rig as I described a couple posts up the board. If I had a good modulation transformer to trade you, I would trade so I could use a solid state amplifier to modulate a high powered RF amplifier.

No I believe you.. I was just joking. 

Hmm.. Solid state drive.. Interesting.  I am not going to use it.

Clark

That got me thinking.. I have an 800 watt Peavy amplifier here.. It has the 70V output.  I could feed this amp with my mixer board.. then feed the 40ohm side like you said and this would hit the 4-400s.  That might work!

Clark

Well Clark, I don't have all the answers but it sounds like your kind of new to this. I don't know how much experience you have working with high voltage? If you are just a little unsure of what you are doing with HV, get someone there at your place to help you that really has built or repaired high powered equipment. Please don't be insulted by my suggestion. I rather you be pissed at me than dead.

We are all here to help.

73

Terry

10,000FT matches the 4CX300A's altitude rating. I found no "Y" datasheet. It is the primary impedance that is odd. The 4CX300 wants a lower impedance, even at 2500V the max volts for modulator service it wants 11K..

But it is possible the tubes were lightly loaded for reliability (lower max plate current) and so the power could have been about half the capacity, or maybe 250-500W. A pair of inexpensive 572B's would work with it and would like a 14K p-p load at 2500V if the power was kept within the xfmr's ratings.

2.4A@97VAC is 235W into 40 Ohms, and 340W is 2.9A@117VAC. - -hey there you go, a 340W sinewave inverter application to run your 400Hz stuff. - or, a WWV-stabilized 60Hz system for all the synchronous motor driven clocks and phono turntables in the house. They used to have something like that in the school so all the clocks would keep the exact same time. I thought the 4 6L6's in the wall-mounted box were the PA system till the maintenance man enightened me.

Just thinking about how to use the thing! Maybe set up a pile of 20 8-Ohm 20W PA horn speakers to make 40 Ohms and play a recording of gunfire on new years eve. Much safer than the usual live ammo practice. Or if you prefer, a recording of bells to ring in the new year, etc. whatever. but there are things to use it for if you are creative.



I'm not enthusiatic about using the high side for grid drive since the Z is rather high and if you draw grid current so there will be some regulation issues. if you don't want it, I can PM my address and will find a use somewhere.. nice piece of iron for sure.

 

Hmmmmm............ is it possible that someone used it as an autotransformer for modulation.

HV fed to the center tap of the primary, one end hooked to the plate of one of the modulators, the other end hooked to the plate of the other modder AND also becoming the feed to the plate of the finals?? Also not having anything hooked to the secondary (40 ohm) terminals. I have seen similar circuits used in other military transmitters.

Just my $.02 worth.
 
                                                        The Slab Bacon

Wait a minute, I want to be first on the glomming list  ;D ;D

Me stinks you'll need a cap & a reactor for that to work and expect something less than 100 % mod.

Ah-hah! I think you nailed it, Frank! That's the only configuration that would make sense. It would give you a 1:1 impedance ratio, DC-coupled for nice low-end response, and it would probably sound pretty good! My VM-4 is wired in 2:1 autotransformer service and works great that way.

I can't see that 40-ohm secondary being used in any tube circuit, except perhaps driving a cathode. There's just no way it would tolerate any high voltages. That transformer is designed to convert gallons of voltage into gallons of current.

Clark: I don't recommend you try using that secondary into any tube circuit. One problem you may encounter is voltage swings across any resistance in the secondary circuit being reflected back to the primary circuit. The step-up on the reflection could be enough to cause internal arcing, which would be the beginning of the end for that iron.

The 1:1 autotransformer is your best bet for hollow-state modulating hollow-state, or backfeed it for solid-state modulating hollow-state as Terry suggested.

It may have been used as mod iron, but it wasn't designed for that, so you'll need to apply it in one of these ways to make it work without damage to the transformer or transmitter.

These taps could have been used for side tone.

Another possible use might be to use it as a Heising reactor.

Just use the primary. It would be interesting to put a LC bridge on the primary and measure the inductance.

It has the high voltage specs for it.

Might not be a gaped core so you probably should try to measure the inductance with a DC load if you can.

That sounds like a good plan Slab!  I think it might work.  Certainly worth a try.

73,  Jack, W9GT

Depending if the voltage rating of the 40Ω winding, it could be wired in series with the line from one end of the primary to the final, and polarised so that it would be additive, thus giving a slight boost to the modulation percentage.  To get full 100% modulation, a better solution would be to use a series dropping resistor bypassed with a capacitor, as used to achieve 100% with classic Heising modulation. 

That's the way I believe Uniden did their AM only chassis for 11 meters....  At least, it seems the config resembles what your iteration came across as.

Theyalso had a secondary on there, which was quite wierd, until I read your post....  It was the feed for the speaker!

Maybe I should pay more attention to this dismissed as crap sometimes :)

--Shane

aside from it being said it was used for this or that, remember the old beachmaster PA system? It couldn't be from one of those could it?

Its not repainted and that sticker is factory.  We had two of them brand new in the boxes.  One is in the 610 as a modulator. The other is on my desk.  This ran the Y tubes. Probably with a reactor.

The boxes match the part number of the transformer.

CLark

please,may i have one?

There is an issue of reading what people are posting....   I never SAID IT WAS FOR A BC610!!!   I said it was used in one for a time period.  The stock mod iron failed and this was used as a temp replacement.  If I misled you guys I am sorry.. I dont know how to make myself anymore clear..

Also.. Please dont say it wont work. in a BC610  It does work. Is it optimal? No.  Does it work as a mod transformer? Yes. 

I have decided not to use it for my Radio. I was going to toss it in and fire up the rig so I could repair other areas of the transmitter while I searched for the money for a proper replacement. But according to the thread and the emails I got its going to BLOW MY ENTIRE RADIO UP.. LOL

Thanks for the help as always guys!! I love hearing about all the interesting uses for this thing!! I am sure someone can use it!!

Clark

BTW, there is a BC-610 modulation transformer available on ebay right now:

http://cgi.ebay.com/NEW-MILITARY-BC-610-STANCOR-MODULATION-TRANSFORMER_W0QQitemZ120429473572QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item1c0a27ef24&_trksid=p3286.c0.m14&_trkparms=65%3A10%7C66%3A2%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

now that would is supposed to work in a bc 610.

I dont have a BC610.   

I love that add..   Selling it as new.. Its clearly rusted and weathered..

C

Good luck with it.

I am going to sell this transformer if anyone wants it.  Trying to find a transformer that will work for the 810s and 4-400s.

CLark

Does anyone see any reason this wont work if I hook the 70 volt output of a large PA amp to the 40 ohm taps and tun the Secondary to the 4-400s?   Still need a choke?

Clark

There is no way that was ever designed to drive speakers. With those HV standoffts even the thought is ludicrous.

If it was really used with 4CX300Y's it would have to be after 1963 and aircraft were able to exceed 10000' by then ::) The height markings mean that it was not built for aircraft use, those are strictly ground ratings.

The Y is substantially different than the A version. 400W Pd, only 110 mc full ratings and of note, spec'ed for AM linear service.

My guess it was part of a cathode driven pulse modulator for industrial use. It would be interesting to see what the frequency response is.

Carl
KM1H

I thought this thread died?? I spelled this out for you in a past thread, I don't see any reason it could not be used. If you can't get adequate modulation, you may have to use a choke. I wish I owned that transformer.

I got the Globe king done so now I want to move back to this project and I just need some help. I thank you for the info.. But thats my questions. Should I use a choke and cap?   

I dont know what it was for..All I can tell you guys is what I was told it was used for. 

C

Hi


Clark to used the modulation Trafo,you must know the load  impedance of the transmitter,
if We used a 2500 v B + for 4-400 and load it for 250 ma than we had 2500 v divided by .250 A = 10 kilo ohm,
sometimes we need a higher impedance ,so we used a 3000 v and load 4-400 for 200 ma we got 3000 v divided by  0.200= 15 k ohm,

so by loading having the right voltage and right loading current we can get the impedance we want ,of course sometimes we get less power out put than the optimal output.

So can we used this trafo to modulate the 4-400  with a P.A amplifier ?
first we must know ,or at least looking by the wight of it,how many watts it can delivered . Since two  4-400  with 2000V loaded to 500 ma has an input power of 1000 watt, and a impedance of  4 K ohm .

If the mod. Trafo has a 2000 watt rating we don't need a choke and a cap ,since the current flow in the transmitter side  is 500 ma , it can't saturate the Mod. trafo ,since the wattage that it used 1000 watt for the transmitter + 500 watt for the Modulator( to modulate a transmitter we must have 50% power of the transmitter input to 100% modulate it.)

But if the Mod trafo has only a 1000 watt rating  we must used a choke and a cap to stop the current that is flowing in the transmitter side of the Mod trafo,So it is not saturated.
 
When we have two 4-400 with 2000 V  loaded to 500 ma we have a 4 Kohm impedance

Looking at this "Mod trafo you have" it has  14 Kohm to 40 ohm ratio,so as when we used it for the 4-400 transmitter  with 4 K ohm than it looks like 11 Ohm  at the other end,
So using A PA with a 8 or 12 Ohm output we can modulate the 4-400 transmitter,since the turn ratio is right.

But maybe the frequency response may or may not  be as good as the trafo is designed fore.

higher  impedance for  a frequency response means more turns / winding  in the trafo,because  needs a higher  inductance (Henry) .

So an output trafo /mod trafo  is design to have enough turns /winding at the impedance of the mod.tube and have a compromise value /inductance for a frequency range, for example we need a frequency range from 500 Hz to 3000 Hz,
Then we choose  1000 hz  to find the inductance at that frequency at the impedance of the  Trans former (modulator tube side)

But of course its not simple as that,winding this trafo.

So when we used a mod Trafo with not the right impedance ,but with the right turns ratio it will work,maybe with a difference  audio frequency response,
more gain at lower audio ,with loss of higher frequency .or the opposite side more gain at the higher tones and loss of the lower frequency/bass tones.

If we get a 6 k ohm primary and a 6 k ohm secondary modulator trafo

Can we used it as 9 K ohm to 9 k ohm,I believed we could as the turn ratio is right.
or used it as 4 K ohm to 4 k ohm ,Yes we can.


Gito