[AMRadio] 75TH vs. 75TL (was Class C stuff)

[Todd Bigelow - PS]

Yes, that looks like a very interesting article in the new issue of ER.
Skimmed it briefly, need to go back and read it thoroughly. I like
improvements along this line that can be added to a rig without the use of
a Sawzall. It certainly makes the rig more usable, and you can feel a lot
better about using it without fear of losing a vital component.

Brett, I recall those days well, in fact much of the old gear I have today
came from the 70s-80s time of  "If you can carry it away, you can HAVE
it". At a hamfest up in Milton VT a few years back I got an absolutely
beautiful 500w mod transformer for $10. Can't recall the name off the top
of my head, maybe Thordarson? It's a 'Multi-Match', this much I know. Has
nice end bells/frame painted in black wrinkle, core is gloss black, and
nickle-plated cap nuts holding it together. This was maybe 8-10 years ago,
you should've seen people look at me when I toted it out - like I was some
kinda looney!

I do regret a bit the mods I did to the KW-1, though - not because they're
permanent(easily reversible), but because the schematic that Uncle Ed
sent me was somewhat difficult to read, and it resulted in components
being removed from beneath the audio deck when all I *really* needed to do
was unsolder and lift one leg of a cap or resistor in the clipper circuit
to accomplish the same thing. I was anxious though, and those guys on
3.885 knew of what they spoke and sounded GREAT, so....I wanted to sound
better than Ed's description of  "sounds like a stock KW-1", at least.

Thanks for the info on the 75TH/75TLs. I have a pair of TLs squirreled
away, and I broke one of the THs by trying to remove if from the socket
before removing the top cap, so that I could gain better access to the
screw holding it on(how ironic). Talk about paper-thin glass!

Live and learn...

BTW, my understanding is that the KW-1 and Johnson Desk KW share the same
mod transformer. They sure look a lot alike, same tube layout and all -
4-250s(later changed to 4-400s) modulated by 810s. Peter Dahl has these
for about $200?

Todd/'Boomer'  KA1KAQ

Brett Gazdzinski wrote:

> Bill,
> This was a long time ago.
>
> I was doing tests on frequency response.
> Putting the signal generator into the audio chain and sweeping
> it while watching the mod monitor.
> When I got down to about 30 Hz POW!
>
> It was no big deal, I paid $100.00 for the transmitter
> including some other stuff along with it.
>
> Mod transformers used to be under tables at fests for
> $10.00.
> That is what I paid for the thordarson I used to replace
> the Collins transformer.
>
> Sure was fun to learn by blowing things up back then.
>
> Different story now....
>
> I also traded a very clean 75a4 with 3 filters, and a
> very clean kws1 for a rack cabinet and rf parts...
>
> Remember when all the tube stuff was worthless?
>
> The new electric radio has info on the mod iron
> protection circuit.
> I use negative cycle loading on all the big stuff ...now...
>
> I don't do low frequency at full power tests now...
>
> Brett
> N2DTS