A 6L6 Modulator article from 1936

[WQ9E]

While scanning another article for a member here I came across this article that might be of interest to some.

[N0WEK]

Thanks!

I love the old style schematics.

[W3SLK]

Hey, there's Don's 'D-104 suspended by springs' microphone! 

[KM1H]

They didnt even know the capability and quirks of that tube yet when the article was published. The 6L6 wasnt released to general sale until late 1935. After that it was a constant bath of 6L6 articles.

Carl

[W3GMS]

They did a lot of things right in the design and it should sound pretty darn good.  They loaded the xtal mike properly in addition the coupling between the first and second stage should allow a good low end.  The transformers are probably not Hi Fi but probably not to shabby!  Maybe a little bit of negative feedback would help but I bet it sounded pretty darn good. 

I have some issue's of Short Wave Craft and they were a great publication. 

Regards,
Joe, W3GMS 

[Opcom]

I like the cover art too. That young man there would be mowing lawns all summer to get the change to buy those parts. One has to love the good old 6L6. It has the be the most popular tube ever made, a pity it is no longer made in metal (see it with a cool heatsink) but the 6L6GC with its higher voltage ratings and low cost has set the pace for today.


The T-8470 mod iron is rated for 75 watts in the catalog #400. - that must give very good performance at 50 watts. In the article, the load impedances are given as 2500, 5000, and 7000 Ohms, but it is the primary that is not mentioned, being 3800 Ohms CT. $10.00 in 1938.

The T-7550 160VA rated plate iron is 870VCT at 250mA DC and interestingly has a bias tap at 80V (in that catalog). also 6.3VCT/1.5A, 2.5VCT/10A (originally intended for four 2A3's), 2.5V/3A, and 5V/3A. Called the T75R50 in 1938. $8.00

The T-8459 driver iron is a 5:1(total) unit with 70KCT pri. to 2800 Ohms 1/2 sec. designed especially for PP 6C5's and PP6L6's. $3.75

The T-5739 speech amp driver transformer cost just $2.25 and is a 3:1(total) unit rated for loads of 10K plate to 100KCT grids. This Z ratio seems strange against the 3:1 turns ratio but it is the recommended loads, not the actual impedance transformation.

The T-7064 low voltage power transformer does not appear in the 400 or 1938 400C catalogs nor in any that I have. That's annoying. Could it be a typo? There are 7061 and 7062 types.. Strangely few transformers end in "4", leading me to wonder about the numbering convention if any. To guess at the cost, maybe $6.50 ?

so there is a paltry $30.50 of 1936 cash tied up in the iron, $478.27 in today's money. It's a wonder more people don't build classical tube stuff, if they had to buy the iron (assuming it was available in mass production). How much did a kid make mowing lawns in 1938? 50 cents each? Someone had a work ethic.

[W7POW]

Thanks for sharing the modulator article.  Saved to disk!