The AM Forum

I'm trying to figure out a couple things on this transformer and find the schematic for the ampifier it is from. I'm told it is the plate iron from an amplifier that was used to boost the BC-610 to 2KW using 833's.

The weird thing is that the BC-610 already makes a huge amount of power, does it not? Would a 2KW amp be enough for it?

As for the models of the amplifier, On one hand, I find the AM-35/MRC (for the MRC-1) On the other hand, the AM-141/MRC (for the MRC-2).

There's a (poor) schematic for the AM-35, but that transformer has dual primaries, whereas this one is 115V only. I have not found good manuals for either that would help confirm what particular set this iron is from.

This is the Amertran unit, 3.75KVA, 115V primary, 7500VCT. Spec 33205 (serial 927500)

All the www turned up was the one AM-35 schematic. Is there a military guru who could possibly share the manuals for these amps so I could study them? Or the schematics, assuming they have component values and voltages?

Thanks!

866's for bias rectifiers just for a couple of 833's ? Ah, heck, it was only taxpayers money ::)

Carl

Hi,

     I guess you would be looking for TM 11-624. The SCR-499
was powered in the field by PE-95 Gen Sets.  Three of em' for
The MRC-2*. The amp was only for RTTY and class C.

   I found a couple "Page Views" of the manual on the web.
For AM and CW you had to disconnect the AM-35/141.

/Dan

Patrick
Are you visiting Area 51 where all of these unique electronic goodies you have been acquiring are appearing in your QTH?

According to those specs both RTTY and CW at 2000W were available. I wonder if the exciter was a BC-610 or T-368. The amp was built by B&W.

Carl

Hey Carl,

    Think it was a T/R switching issue.. It was used with the
SCR-499, 610-E and later.

/Dan

"According to those specs both RTTY and CW at 2000W were available. I wonder if the exciter was a BC-610 or T-368. The amp was built by B&W."

I was wondering the same thing, Fred.

It's like he's got the truck parked near the back fence of the depot or something, and it's after sunset.

I only have 2 of those xfmrs. Shame they can't take a full wave bridge on the secondary as with the late BC-610 and T-368 oil filled units.

If you have two, then it's a good setup for separate modulator and PA power supplies. Each can draw from one side of the 240V supply.

I could agree on a bridge if they would take it, but for what tubes and service?
FW Bridge 3.75KW DC (about max) CCS would be 6466V @ 575mA. To what use would you put that? There was the Elenco Commander a SSB amp doing something like that with a 4-1000.

Too bad anyway, for it not being more versatile, but we get what we get, and whatever junk people drop off, it's what it is. 8-)

what to do with 3200V?
Two three class B 833's - 3300V @ 780mA, 1900W out - used as intended.

Or how about three-four 3-500Z's for a 2500W AM amplifier with lots of plate dissipation. I don't consider 3-1000's because they are big $ on short notice.

- just examples. I'm not building anything with it now.

It -could- power that 2KVA audio amplifier, but 3200V is low for 4-1000's, especially old used ones, and it's supposed to use 4750V. I have a nice Basler unit that ought to fit that need, either 4000 or 4500VDC @1A.

Most of this nice stuff I end up with has come from TX, NM, AZ, CA, WA.
An excimer laser convertible to N2 came from CO.

The chart shows why this transformer is interesting. There are a lot of tubes that use 3200-3300V.

OK, I admit to helping Pat get this.

Lugged from LA a few years ago, I gave it to another local ham, and he traded it to Pat.

It was in an original welded angle-iron frame, along with the rectifier tubes, choke, and cap.  Most of it was stripped, no info on it.

An original part in the unit was dated 1943, so this is definitely WW2 vintage iron.

73DG

I also have an exact "looking" transformer type "w" but my plate says 6200volts and 2kva .I wonder where mine was used?
 I also have a Signal Corps transformer made by Lionel that is oil filled and rated at 2500v @ .3amps or 2000v @ .5 amps.I havent been able to find info on either one.

The first one will only be good for 200ma but the second one will be useful.

 You can do  lots with yours !  Good Luck

  Rick

Lots of amplifier tubes out there these days for that voltage. If CCS is 600 mills it would do a lot more in a hamplifier.

I'd think the big problem is finding a good choke for the supply.

Anyway these xfmrs would most likely zap the center tap over to the iron with a FWB.

With some old iron you can remove the end bells and reroute/insulate the CT;  hipot test before using since not all can be repurposed. I also toss the bells and mount terminals on a phenolic or fiberglass strip and aluminum bracket; saves space and a lot of weight.

Is there a way to do non-destructive insulation testing?

With a hipot tester and select the current limit wanted....usually in the 1-10 microamp range. Surplus commercial testers have it switch selectable and HB requires many megohms of series resistance. Here is a HB example which I built many years ago using a sign transformer and FWB instead of doubler to get up to about 20Kv (limited by the HV meter resistors I had available)

http://www.somis.org/BVT.html

A surplus 0-5Kv tester was $30 at the local "junk" shop which suffices most of the time for my needs.

Old topic but specific to this reply, the manual for the AM-141 amp the transformer went in is on the bunkerofdoom.com site now.

AN/MRC-2 Radio Set. TM 11-624A, 2KW Amplifiers AM-141A & AM-141B /MRC for BC-610 138MB NEW! (http://bunkerofdoom.com/lit/AM-141/TM11-624A.pdf)
AN/MRC-2 Test STD REP-455 for AM-141 Amplifiers p-p 833s running 3300V@1.3A - 5.8MB NEW!  (http://bunkerofdoom.com/lit/AM-141/am141mrc.pdf)

Thanks to CECOM librarian!