The loyal and faithful Lafayette TE-20 Tube Tone Generator did its thing, especially since I upgraded it by adding a 600-ohm output transformer to give it a balanced output.
This into the LPB2-20 Exciter Audio In, 600-ohm balanced, the VU meter swung into action and on a portable radio held close to the dummy load there it was at 570 on the dial...... 440Hz.
It looks like we're both getting
somewhere!
I just opened the LPB RC-6A up.
My friend put a lot of new electrolytics
in. He says it's easy. Yeah! Easy
for him! The broken coil doesn't really
look broken, but maybe I'm missing
something.
Concerning the two caps that you tune
for max output. I thought they were
coils, but they are caps. It looks
like these things are tuned to the
end of their range. They look to be at
minimum capacitance. If I am correct,
this unit may be at the upper end of
it's tuning range (at 860 kHz.) This
particular RC-6A
may only be for the low end of the band.
RFB, I'll have to look at your notes. I
thought you said most RC-6As covered the
whole AM band. So maybe I'm wrong there.
I also see an inspection sticker on the
inside. It looks like 10/5/71. But the
"1" in "71" is a little squiggly. It could
be a badly written "3." So it might be 10/5/73.
RFB, I think you knew exactly when this unit
was made - start to finish. 1971 seems to
make more sense.
The only other thing I'm observing right now is,
sometimes there is a whistle, maybe 6 to 8 kHz.
If you tap the middle 6AL11, it stops. I remember
this happened back in the old days. Maybe the 3
new 6AL11s will stop that problem. Maybe.
I have had this thing for about 30 years, and it
has never been used on the air.
I am glad to have it back.
Bruce, Frog Horn 860
P.S. Carl - just read you are getting 440 Hz
through!!!! Congratulations!!!!!
No..I said that LPB did make RC-6A's that could cover the entire MW band..but you had to specify that when the order was placed.
My unit was just such a "all band" unit because I ordered it that way. It had the adjustable inductor coil.
Obviously your unit is geared for the low band and has a different output tank.
Carl, take note of the manual about the audio modulation percentage. 100 indication on the meter is way over. 100 percent modulation occurs at just under the 50 mark with program peak. Once set, the meter won't display audio like that of a meter on an audio console.
You can refer to the front cover insert of the cabinet for further info on the audio setup.
However none of that is relevant until you get that exciter back into the cabinet, driving the final amplifier module. Remember this transmitter uses a linear final and is not a collector modulated transmitter. There will be re-adjustments once its all together and operating.
Bruce..the 6 or 8 hz whine is probably one of the elements inside vibrating, sure sign of the tube being old and in need of retirement.
Glad to hear both you and Bruce are making progress!
RFB
Not doing any more transmitter work tonight, only sitting back and bragging about today's accomplishment. If I had a date sitting here she would already be snoozing as I go on about meters and dummy loads.
I must have had a good instinct, because I set the tone on the meter at about 55% since higher than that sounded too high on my radio.
Looking at the stars and realizing that I am a star, I wonder many things. I wonder what would happen if everyone in every house hooked up a carrier current radio station?
Thanks RFB. I'm glad you are with us!
Bruce
RFB, I was looking back at your post
about your homemade board and everything
else you had working there. That's
amazing you were able to assemble such
an incredible station. All the people
I knew THEN were either running Part 15 or
pirate radio. I had heard of a few
people running CC stations out of their
houses, but it's just Part 15 folklore.
Except there was some kid who was on 640 kHz
and covered a big area. He had a really
cool station in a big closet. Pictures
of this station were in one of the
magazines of the time, but I don't
know which one. Maybe if was Elementary
Electronics. I'm not sure. I do remember
his station ran a program called "Rock
Over London." This was sometime in the
1970s. I was particularly taken by his
great installation in the closet. It
was a small but very beautiful studio.
This kids downfall was when he tried to
get on FM. The story I remember was that
a local engineer did a legal Part 15 set-up,
supposedly, but something went wrong and
the kid was busted. It was too bad. I
think he was really trying to do a legal
operation. He seemed to cover a wide area,
so it must have been neutral injection.
Of course, my friends and I never knew about
that approach. Things might have been very
different if we had.
Reviving this old gear is sort of like
a time machine to me.
I love this old stuff. A lot.
Because of my limitations, my progress on
the RC-6A will be very slow. I will be
happy just to have it's signal covering the
house and yard for now.
Carl will be taking the lead on this
until I can find a way to get the LPB
unit onto a better channel. I'll have the
new tubes into the transmitter in a couple
of days. We'll see how that works.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2
I remember restoring an old McIntosh 50 watt tube stereo amplifier a couple decades ago. Had one heck of a time finding certain parts which were proprietary, some of which I had to come up with alternatives. Certain sealed coils in the receiver section and some hardware pieces, not to mention no schematic to reference. Thus took the time (about a week) to manually draw up the circuits then moving on with the rebuild.
It was enjoyable and the best part..watching it fire up and pumping out 50 watts (actually about 62) of pure warm milky stereo audio. Receiver section worked great and I think it even had a bit more sensitivity and didn't spit out the garbage like the other superhets did, (I cheated and added some custom filtering and shielding) and lit up the evening with the orange glow of filaments.
Wish I was there with you Bruce to work through that RC-6A unit. There is nothing like seeing the old stuff come alive and rattle the cages of all the new things that usually end up in the dumpster shortly after the warranty runs out!
Built to last, built like tanks and it takes a heck of a lot of work to kill one! That is unless you have a drunk brother who slams his car into the wall of your room! 😉
RFB
I really enjoyed the message you
just posted. I just came home
from one of my jobs and my back
is sort of messed up. (It will be
OK.)
So I will have some comments for you
but I will have to post them a little
later.
Thank you for the cool stories.
Bruce, DOGGRADIO STUDIO 2
Hope the back issue isn't serious. Rest and take all the time needed to get better, as well as take time to restore the RC-6A. Your health is far more important.
At least from your description of the RC-6A in it's current state, is functioning pretty well regardless of the whistling tube and messed up tuning inductor on the output tank. And thanks to your good friend who re-capped it and inspected it, makes the rest of the restoring project that much easier to deal with.
Take a break, relax and attend to the back problem first. No one is going anywhere, and the RC-6A won't either. 🙂
To your good health!
RFB
Thank you for your kind words. It means a great
deal!
Sitting in front of me is a box containing 3 new (NOS)
6AL11s.
Later on tonight, I will have time to try them in
the RC-6A.
I'm really excited about this!
Soon, I will have a couple of questions for you
about the transmitter.
In the meantime, thank you again for the kind words.
I will return soon.
Bruce, DOGGRADIO STUDIO 2
I just put the "new" (NOS)
6AL11s into the LPB RC-6A.
The tubes are from Sylvania,
which makes sense.
It sounds good. Very low
noise, no hum. This wonderful
piece of radio history is built
like a tank.
I believe it is achieving 100 percent
modulation. (I'll have to pull out the
scope to really know, but I'm not ready
to do that yet.)
I saved the old tubes, because the
transmitter sounded good with them
last night. (Unlike last year - before my
friend in New Jersey worked on the
unit.)
I'm going to let it burn in - in the
next few days (only when I'm around,
though.)
And then, RFB - as soon as I can -
I will have a few questions for you.
These questions may not be easy to
answer - but you are THE MAN.
Best Wishes,
DOGGRADIO STUDIO 2
Sounds good Bruce! Keep the old tubes around as emergency backups. If they still work, they are still useful for that purpose.
And I will do my best to answer the tough questions. 🙂
Just found this that may interest you: LPB RC-6B .
Be good to have handy for those impossible to find parts!
RFB
Thanks RFB. Well, I don't have the
funds for that second transmitter.
However, I urge somebody here on the
site to get it and try carrier current.
You will be preserving something very
special.
It looks beautiful and the frequency is
sure great - 530 kHz. Unless you have
something on 540, 550, or 560 that is strong -
530 kHz would be perfect.
I'll be right back.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2
Still, a member here on the board who is
good with tubes and high voltage should
snap it up. I see it has no case, though.
So, without a case, you HAVE TO BE GOOD
WITH TUBES AND HIGH VOLTAGE OR YOU COULD
GET KILLED. There. I think it was a
good idea to say that.
Perhaps my urging for somebody to get it
is premature. However, having it just sit
out there doing nothing sounds a little sad
to me.
Bruce, DOGGRADIO STUDIO 2
A good friend here just located a crystal
for 1020 kHz for my RC-6A. It may or
may not work out for various reasons,
but the cost was is low I am going to
try it.
1020 is blank during the day. There
are no locals on 1000, 1010, 1030,
or 1040. So again, it is worth a try.
At night, KDKA 1020 bombs in from Pittsburgh, PA.
However, that's at might. I don't mind
running a daytime operation. As we all know,
KDKA is one of the first stations that came
on the air in the 1920s. Some people have
mentioned a few other stations that maybe
came on just a little bit sooner, but I don't
remember what they are or if the info is correct.
In initial tests, I don't expect to be covering
any big area, anyway. For a while, it will be
just in my house. Maybe for quite a while.
I plan to be very careful when I go to couple
into the AC line. By the way, KDKA is one of
those few AM stations on this side of the U.S.,
whose callsign starts with the letter "K."
There is another one nearby. It is KYW in
Philadelphia, PA. KYW is on 1060. I think
I've got that right.
So, Mr. RFB, stand by. I will have these
questions for you fairly soon, I hope.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2