Mod Transformer Info Needed

[W8UJX]

Anybody have a data sheet on a Thordarson T21M64 modulation transformer?

Tks,
Jerry, W8UJX

[W4RFM]

Hey Jerry,
All I have found so far is that it is rated for 300 watts of audio, with 250mA max on the primary and 500 mA max on the secondary, and it cost $83.00 a long time ago.

[W8UJX]

Thanks Bob,

I thought it was rated at 300 watts but I did not know the current ratings.
It cost considerably more than $83 a short time ago.  Hi... 

It has two what appear to be center tapped windings on each side and I'm not sure which side is the primary.  I would guess the rating on the secondary is with both windings wired in parallel.

I did a test with 110 VAC RMS applied to the primary(?) pins 1-7 with the two windings in series, pins 3 and 4 jumpered.  With both windings connected in series on the secondary(?), pins 9-10 jumpered I measured 89 VAC RMS across pins 7-12.  So I guess primary to secondary in that configuration is step down.

Jerry, W8UJX

[kb3rdt]

Thordarson multi-match 300 watt

http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips1004.pdf

[W7TFO]

The tubes recommended for use as modulators are:

HK-54
203A
211
805
808
811
838
TZ-40
T-55
35T
100TH
HF-100
ZB-120

They purposely didn't publish impedances, as that is so variable under class 'B' conditions.  Go with the ratio specified and try different combinations for best results.

73DG

[W8UJX]

Thanks for the link to the info for the mod transformer Carl.  The one shown is the one I have.

I was thinking of building the modulator shown in K1JJ's quad 813 rig and driving it with a Heathkit Hi-FI amp.

I connected the transformer as shown in the schematic and applied 120 VAC RMS 60 Hz (measured 119.2 VAC) from the wall socket to the primary.  The voltage at the secondary (no load) measured 68.6 VAC RMS so I guess the way the terminals are connected (primaries in series and secondaries in parallel) is close to 2:1 step-down which was recommended by K1JJ.

I'm assuming the transformer will pass the 60 Hz frequency.

Jerry, W8UJX

[KE6DF]

Thanks Bob,



It has two what appear to be center tapped windings on each side and I'm not sure which side is the primary.  I would guess the rating on the secondary is with both windings wired in parallel.

I think it's a new version of the 11M77 -- same ratings, but different packaging.

Connection info on the 11M77 is available on AM Window

[W8UJX]

Thanks David,

119.2 VAC RMS conected to the primarys wired in series produced 68.6 VAC RMS on the secondaries wired in parallel.  119.2/68.6 = 1.737.  The data on the connection info, Turns Ratio (Pri to Sec) says 1.73 so I guess that is the correct information for this transformer.

Where else would I find answers to questions like that except AMfone.

Jerry, W8UJX