The AM Forum

Are you positive that is a BC-610 plate transformer?  Have you tested it with voltage?

The one in the photo looks identical to a different transformer that I have often seen at hamfests.  They are about the same size as the BC-610 transformer, but the HV  secondary has no midtap, but designed for a full wave bridge rectifier.

A BC-610 transformer should have two primary taps, one to give a DC output voltage of 2500 and the other, 2000 volts.  The earliest ones, identical to the original Hallicrafters HT-4, has only one primary tap, to give 2000 volts DC.  The secondary has 3 big insulators, with the one for the midtap identical to the other two.  The one pictured appears to have only two big HV insulators.

Open frame type BC-610 transformers are usually made by Stancor, but I have seen a few made by other manufacturers, which might possibly explain the different appearance, but I would check it out first to make sure.

Don,
      I let the smoke out of one that looked EXACTLY like that one a few months ago. it was made bt the American Transfoma Company. 150+lbs and something like 62 or 6300vct with a 120v primary. The center tap was internally grounded for FWCT rectification at gobs and gobs of current. It died while idling in standby, as best as I could figger it was some kind of insulation failure.

                                                       The Slab Bacon

Is this a BC610 plate xfmr? 

Nameplate: 52C046  Stancor

Sure is. Short the primary and run 125 volts into the secondary with a 100 watt lightbulb in series for a week or so before trying it out.

Ok.. Yeah.. This looks much different. I guess this is not a 610 transformer.  I talked to the guy I got it from and he said it was 6kv also.  The Center tap is on the side of the Transformer.

Anyone have any idea of the current rating of the thing?


C

Found the tag..  American Transformer company.  Plate transformer.  6300V.  Cant read the rest of it.  It has Two taps on one side and 4 on the other. The Center tap is on the side.   Looks like 2.0 amps??? Its real hard to read.


What the heck was this used for?

I'm answering about RKW's xfmr in the pix.

How much does it weigh and what is the size of it. It may be a transformer that was used in the BC-610 amplifier know as  an AM 141. That baby would produce 3000 VDC at 2 amps. It would weight about 200 pounds. It ran on 115 volts.

Yes. You are correct..  I have searched the net like crazy.. This Trans is from an AM141

AM-141(*)/MRC
Amplifier, RF, Transmitter, 2-18 MHz. Used with AN/MRC-2(*) RTT configuration to extend range of the BC-610(*) transmitter. Output: up to 2 KW CW or RTT. 115 vac 60 Hz 1 ph, 50 amp. TM 11-281, TM 11-286, TO: 31R2-2MRC.

I have the manual for the AM 141 and I've seen one of those transformers before. That's why I thought it may be one of those beasts.

Way back in the history of Electric Chairs one state had a mobile unit. Now if that punishment ever came back, all you will need is a 120 volt generator :o :o Electrifying idea ;D ;D

It should have come with its own set of rollers. 

Heavy Metal Rules.  Ya gotta use that tranny to build  A REALLY BIG RIG!

The trouble is the 120 volt primary..  If it was 220, I would keep it.  It looks to have 3 primary taps. Nice for lower power LOL. 

I cant ship it.. So if nobody local wants it, I will just keep it for a rainy day.

Clark

If you have a real stiff 120 volt source, I would consider using it. Back in the day when most homes only had a 5 KVA pole pig strapped to the pole, lights would blink when a transformer like that was used. A few hams would purchase a 220 to 110 step down transformer to run large plate transformers like that to eliminate lights  blinking. I can just see the brown out when doing an east coast atomic HELLO on the rig.

It won't cost you anymore to run that because you are buying KW's. Some people think that lower voltage means higher electric bills.

TRP got the thing from me.  Too little for the planned things here, he thought it would go OK in his 'big rig'.  Things and plans change, it was a bit too large to fit the existing footprint IMHO.

I can vouch for it's veracity, or at least that it works OK.  I got it from KO6NM in LA. 8)

Dennis

I have several 240 to 240/120 5KVA isolation transformers rescued from HP minicomputers. Just the ticket to use that big plate iron.  Can't bring myself to discarding them, but if anyone needs one, they are available near Atlanta, GA.  Over 100 pounds, so can't ship, but feel free to contact me when you are in the area, free for the taking. (Or, arrange to meet at one of the many festers I attend each year!)

I agree..Almost everyone has a 150 or 200 amp home service these days. A 30A, 120V branch circuit  = 3600 watts.

In the old days when a 60A service was customary, yeah, you'd be dimming the lights with that bad boy. I've got a 25 KVA line transformer out on the pole. In the old days, it would have been a 5.

I have a 30amp 120 volt line run into the shack. Heavy wire. I put it for the Globe king 500C and other Transmitters. Recievers run off a seperate 20 amp line with 30 amp variac.  If nobody local wants it, I will keep it and maybe use it some day. I am just trying to get up the rest of the money to finish my Transmitter.

Clark

All you need is another transformer. Run each on one side of the 240 feed and parallel the secondarys in proper phase.

That is my problem, I had a bunch of plate transformers, but none with the right outpoot voltage I needed for my 4X1 rig. I also needed a 120v primary to boot!

I dont have 240 piped into the shack, and also all of the rest of the transmitter is 120v. (exciter, control circuits, etc) I would have killed for that transformer a few weeks back.

Thanks to Skip, he fixed me up with something that would work, I ended up running a 240v transfoma on 120 and getting 3200vdc under full load out of the filters. The 4X1 now gets nice and "red in the face" and is running fat and happy.

High power transfomas with 120v primarys (at lease ones that are good) are getting harder and harder to find these days.

You should hang on to it just in case. One never knows what the future holds.

                                                    the Slab Bacon

Aside from the TM's for the BC610 installations, has anyone ever even seen or owned an AM 141?  I gave up years ago on ever locating one.  I imagine the ones that made it out into surplus were picked over by the scavenging folks back then.

In the last five years I have seen two come up for sale on Ebay. Nobody purchased them. I'll search my computer to see if I saved any data on who had them up for sale.

It is rumored that someone has one in storage in NH but I can't crack the case.

Any idea what tubes the 141 used?  Any other data?

C

Both my homebrew rigs  run off 120 volts.  The 8005 rig uses a common power supply using RCA broadcast transmitter iron @ about 1350 volts. 

The HF-300  rig uses two separate supplies.  The rf power supply plate xfmr is made by Kenyon, taken from a pre-WW2 Hallicrafters HT-4.  I originally had a UTC plate xfmr  for the modulator until it crapped out.  I replaced it with a BC-610 transformer with the 2500 volt tap connected, with nearly identical performance.  Both supplies  run off 120 volts.  I get a couple of volts drop when I key up the rig, but nothing serious.  I use very heavy wire to run power between the house and shack, and take power from a circuit that used to feed an electric kitchen range, good for 40 amps @ 240 volts.

One useful trick I have found useful with 120 volt power supplies, if you have 240 volts available:  Connect the modulator and rf final plate supplies to one side of the line, but connect the filament transformers and all other power supplies to the other side of the line.  That way, when the modulator and final draw plate power and the 120v mains voltage sags, the voltage on the other side of the line will be boosted by about half the sag voltage.  The reason for this is that voltage drop in the neutral wire adds to the voltage that appears on the other side.  This way, you get a slight boost in both audio and rf drive voltage just when you need it the most: while the modulator and final are delivering maximum power.

One exception: connect the class-B modulator bias supply to the same side of the line as the modulator plate transformer, preferably right at the terminals of the HV plate transformer.  This will reduce modulator distortion by slightly reducing the class-B grid bias as the plate voltage sags.  Of course, this works only if you don't use electronically regulated bias. 

For absolute minimum class-B amplifier distortion, whether it be an AM modulator or slopbucket leen-yar, you want the bias voltage to sag at exactly the same percentage as the plate voltage.  This could be easily designed into an electronic voltage regulator that is controlled by sampling the plate voltage.  One of the reasons why it is always recommended that the plate voltage be as well regulated as possible is that simultaneously sagging plate voltage and rising bias voltage may add several percentage points to the distortion of an amplifier. Amplifier tube grid current tends to cause the bias voltage to rise.

The 813 rig here runs on 120.  It's on a dedicated stable 20amp circuit. Under full load 400w strap 100% sine wave modulation it may drop 1 to 2Vac over a 40ft wire run.

BC610 transformer is rated at 550 ma if I rememeber. I ran a pair of them across a 240 line with both referenced to neutral. Then came into a pair of NIB UTC CG310s

Good stuff Don,I understand the auto transformer effect.  I had the neutral on my 7 KW generator come lose and when I put a load on one side, it boosted the the other side to some unknown voltage and burned  out a surge suppressor plugged into the wall. I was lucky I didn't have a fire.  

Hello Clark, The AM -141 used a pair of 833A's in push pull for RTTY and CW only. Those amplifiers were most likely used in a command setting perhaps for people like General Eisenhower. The average HQ operation would have used the 610's in the big WW2.

That looks like the electric version of your old toilet avatar Terry.

Yes, too bad I had to remove it. Those were the fun old days. I still have it if and when I find an appropriate venue for it, perhaps it will be seen again in all it's glory ;D ;D

ps I didn't think anyone would have remembered it ;D ;D

My good buddy Herb didn't like that one ;D ;D