Looking for CHT Series T15D82 Connection Sheet...

[W1AEX]

Hi,

I'm wondering if anyone here might have connection information for a Thordarson CHT series T15D82 15 watt multi-match driver transformer?

I have searched the archive here and at the bunker of doom and can find catalog information, but no connection information for the patch panel on the side. Some ancient notes on a 3 x 5 card that came with it indicate that depending on the jumper settings used on the patch panel, it can match 8 ohms - 600 ohms to the grids of a modulator. I'd like to use it to drive a pair of 811's.

Thanks,

Rob W1AEX

[Opcom]

I wondered where I'd left that transformer..

srsly, no diagram in the Bunker.

[W1AEX]

Yah, looks like I'm coming up dry with this one. I'm using an old push-pull 6L6 type audio output transformer from an old junkbox Scott amplifier in the interim, but this would handle things a lot better if I can figure it out. It looks really pretty next to it's big brother, the CHT 300 which is in the modulator deck.

Ah well, I'm sure a connection sheet will turn up sooner or later. If not, I'll play with a sig generator and oscilloscope and see what I can figure out.

73,

Rob W1AEX

[The Slab Bacon]

Rob,
      If that transformer is typical of the rest of their multi match series, it connects as follows:

The 2 terminals marked "G"  go to the grids to be driven. The terminals marked 1.5, 2.00, etc are are tied together to form the center tap for the secondary winding. (the secondary is split) Use 2 marked the same for center tap of the secondary. The numbers correspond with the step down / step up ratio. (turns ratio) The impedances will be a reflection of what the transformer sees at either end.

Usually those things also have a center tapped primary as well, so you can use a balanced (push pull) or a single ended driver.

It is prolly an actual driver transformer, as "line to grid" type are usually marked differently.

That is a pretty strapping driver transformer, prolly designed to drive class-B grids.

                                                              The Slab Bacon

[W1AEX]

Hi Frank,

The bottom solder lugs are arranged as seen in the photo, with the two "G" lugs connected to the corresponding "G" lugs on the patch panel. Those do not seem to be connected to any windings, so I assume they have to be patched over to another side panel plug once you determine the impedance of the grids to be driven. Each of the two "C" lugs on the bottom panel connect to one half of the patch panel on the side. I assume for push-pull operation those would be joined together to form the center tap for the secondary.

The bottom solder lugs then offer 3 connection points to the primary, with two labeled as 500 ohms, and with the one all by itself labeled as 500 ohms (COM) and the other two designated as either A or B. The common is definitely not a center tap for this winding. It is at the end and the other two taps are near the other end of the winding. So the primary looks like it is a tapped single ended winding.

I did decipher this note which was written in faded magic marker on some masking tape.

8 ohms          8 ohms
.75                A 2.00
with jumper at 2.00 - A 1.40

Another faded note indicated the following:

"A and B on ratio taps correspond to primary A or B tap used"

Based upon what you said, and from what I can see, the internal windings of the transformer looks like the diagram I made. I have not tried it yet, but it looks like primary "A" and "common" can be connected to an 8 ohm amplifier (Or possibly A and B would form an 8 ohm tap?), and C + C are tied together to form the secondary center tap. The grids of the modulators are tied to the 3.15 taps and 1.40 is jumpered to 2.00 on each of the secondary windings. If I have time, I'll mess around with it this weekend to see if it matches up better than the transformer from the junkbox Scott amplifier.

Incidentally, an old Viking II (CD version) that lived at your place for a while ended up here and offered up a few parts that helped me get the Viking III back up and running. I found the stash of 100 dollar bills in the oscillator compartment, thanks a lot!

73,

Rob W1AEX

[The Slab Bacon]

Rob,
      I had a massive brain-fart. It's been a looonnnngggg time singe I hace played with one of them. Your's is definately a "Line to P-P grid" transformer. That is one of the nicer ones with the terminals on the bottom instead of the "flying leads"

On the "patch panel" side of the transformer, you hook jumpers grom the terminals marked "G" to the corresponding turns ratio desired (numbered terminals) to get the ratio you need. The 2 CT terminals on the bottom are tied together and used as the center tap, and the 2 terminals on the bottom marked G go to class B grids to be driven.

That is the ideal transfoma to drive a pair of class B modulator grids with something like a Ranger.

Like I said, pardon the brain fart, but this happens as we get older

                                                             the Slab Bacon

[W1AEX]

On the "patch panel" side of the transformer, you hook jumpers from the terminals marked "G" to the corresponding turns ratio desired (numbered terminals) to get the ratio you need. The 2 CT terminals on the bottom are tied together and used as the center tap, and the 2 terminals on the bottom marked G go to class B grids to be driven.

Ahhhh... that makes sense! I'll have time to mess around with it tomorrow to see if I can get a more efficient match than I'm seeing with the backward output transformer. Should be pretty easy to configure.

Thanks for the explanation. If you are around on 3.733 later tomorrow I'll be making some noise there!

73,

Rob