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 Post subject: 1947 Thordarson Compressor Expander Amplifier Circuit
PostPosted: Nov Thu 14, 2019 6:49 am 
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Joined: Apr Sat 04, 2015 6:15 am
Posts: 1339
Location: Dos Rios, CA. region
Here is a project that has taken some time to put together...I originally received the T'dsen control transformer 20A26 (with instructions, schematic)
a couple of years ago from fellow Nor Cal ARFer Norman B.
The project to put together this amp for my own use was a bit overwhelming at first, as I've not ever put anything together from scratch before.
For almost the past year I've studied many ancient compressor/expander circuits ...contemplating building, acquiring parts...
then realizing after learning a bunch, that this circuit doesn't seem as difficult to troubleshoot as the 6L7/ 6386 (expensive) and 6BC8 type circuits,
so here I am back at square one.

Again, this has become one of my "hybrid" repair projects, as the only similar T'dsen/Meissner "products or kits" from this era using 6B4G's in P/P are a expander only T-31W11 and the T-31W10AX, both of which call for different transformers and ratings than the ones used in this parts list.
This time I used a Scott Radio Labs 800B chassis for base of operations, a little speckled but not too bad after scrubbing with Brasso.
A potted A.D.C. power transformer with similar ratings as the inobtanium T'dsen 22R32, although I'm adding a Chicago potted filament transformer
to make up for an extra 6.3 volt winding not present in the ADC.
The 20C53 filter choke will mount underneath below ADC in it's own potted Scott IF can and the ouput transformer is pulled
from a Scott 16A Metropolitan ( this matches another inobtanium T'dsen 22S70).
Fortunately I've saved all those fancy dancy 5692's, 5693's and not sold them yet , whew!
Any suggestions ya'll might have to "mock up" pictured here, feel free to post,
I'll be posting the schematic soon.

Thordarson Compressor Expander 11 12 19 9.JPG
Thordarson Compressor Expander 11 12 19 9.JPG [ 919.12 KiB | Viewed 155 times ]
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