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 Post subject: RCA Application Notes
PostPosted: Dec Mon 14, 2020 12:54 am 
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Joined: Mar Sun 22, 2020 5:56 am
Posts: 1992
Location: Arvada, CO, 80004
Outstanding hints for designing radio, televisions, and much more. Some things that stuck out to me were:
http://www.one-electron.com/Archives/RC ... Notes.html
Characteristics of the 868 Phototube
Lissajou's Figures
Operation of the Improved Type 906 Cathode-Ray Tube at Low Voltages
Operation of the 6L6
Tuning-Indicator Circuits for the 6E5 and 6G5
Operation of the 25L6 in Typical Circuits
An Audio-Frequency Curve Tracer Using a Cathode-Ray Tube
A Two-Terminal Oscillator
The Operation of Phototubes
Operation of the Gas-Triode 0A4-G
Operation of the 6SA7
Operation of 50 mA Tubes by the 117N7GT
Mixer-Oscillator for FM & AM Using 6J6 or 19J6
Reduction in Peak Inverse Voltage Rating of Type 1B3-GT (X-Ray Galore!)
PPI Scan Generators for Use with Display Storage Tubes
AC-DC Stereo Amplifiers Using Output Tubes Having 100 mA Heaters

_________________
Electronics are filled with smoke. It’s my job to put the smoke back in when they fail.
Cheers,
Jay


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 Post subject: Re: RCA Application Notes
PostPosted: Dec Sun 20, 2020 8:17 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 449
Location: Green Valley, AZ, USA
Hey Jay

Thanks for putting this historical stuff up. Very interesting reading. I wish I knew about these notes earlier in my tinkering.
GE and GR had some good notes too.

The note on shielding inductors is interesting and leads me to wonder if what it does to coil Q, I suspect it swamps Q.. This leads me to wonder what the effects of mu metal and other composition sheilds would be.

RCA 1935 AN-48 Graphical Determination of the Decrease in Inductance Produced by a Coil Shield

Hank


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 Post subject: Re: RCA Application Notes
PostPosted: Dec Mon 21, 2020 4:35 pm 
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Joined: May Sat 14, 2011 5:42 am
Posts: 4222
Location: Ft Worth TX
Shields, grounding, swamping, reminds me of a war story:

In the waning days of Ampex support, suddenly our half $M commercial machine stopped playing color. I narrowed it down to the burst gate, 2N2222 driving the primary of a pulse transformer, secondary driving a FET. The pulse went in but it didn't come out. Even tried changing values in the primary ckt.

Phone to Ampex, the transformer was NLA. "But we NEED one!" Well, we've got some scrap boards nobody can fix, we'll take one off and send it to you. Ahh. Uhgg. Same thing. Don't know what led me to do this, but I ran a wire from the transformer ferrite core to the ground plane and PRESTO, back in business.

I still don't know exactly why, but the core needed to be grounded for the transformer to work and that ground had lost continuity. Not only that, but the fack-tree guys who invented the thing apparently didn't know either. That's why the boards were scrapped.

_________________
"Enjoy the fair, George."


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 Post subject: Re: RCA Application Notes
PostPosted: Dec Mon 21, 2020 11:44 pm 
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Joined: Dec Tue 23, 2014 6:51 pm
Posts: 2366
Location: N. Palm Bch, Fl.
Back in the day our controllers used 7 wires for 1 character pickup. Software told it which terminal it was coming from. The keyboard was powered by 5 V from the controller and each lead had a zener on the board. Intermittent wrong letters were a problem. Change the board and fine. The scope showed low 5V on some pins. I checked some boards that came back as refurbished and some had the same problem. I talked with the manager of that department and the test machines don’t check the output voltage. The end result after a while was. The problem boards came in mostly from the SE and Mid West. They felt the problem was lightning and different power sources between the terminals and controllers. They decided to check all terminal boards by hand for low voltage output before shipping and zeners were sent to each office. No bonus, but I did get a Thank You from him.
Engineers are great, but they’ve never been in the field and have no street smarts.
The field is not an ideal environment.

Freeman


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 Post subject: Re: RCA Application Notes
PostPosted: Dec Tue 22, 2020 8:17 am 
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Joined: Dec Sat 28, 2019 4:18 pm
Posts: 1088
Location: Corinth, TX
Freeman wrote:
Engineers are great, but they’ve never been in the field and have no street smarts.
The field is not an ideal environment.
Freeman


And you cannot trust many with soldering equipment. (I have seen pictures of some of your [collective] work. Many of you are exceptions to that rule.)

In the late -60s, I was a young corporal working at MCSC Barstow in the HF/SSB radio shop. We also served as a catch-all. If it wasn't test equipment, HAWK, or radars, we caught it. Depot got a contract to design a test set for one of our military generators (PU-608 comes to mind, I think). Good sized unit, about 2.5 ft cubed. Engineers upstairs designed and built it . . . and it didn't work.

They sent it down to us along with all the paperwork. Leadership put together a 4 man team: one civilian (adult leadership, I guess) and 3 marines (WE weren't tied to time clocks). We opened up the case, and it LOOKED like a military test set. Alas, when we opened up the T/S, the build quality was abysmal. Solder bridges abounded. We stripped it completely and rebuilt it, working from the back forward and bottom up, building an assembly manual as we went. We checked everything. Found a few minor mistakes. We let it set overnight, shifted the inspection team around, and double checked. Found a couple more things we weren't happy with.

Smoked test, and it worked.

But all of that created a lot of disillusionment at a pretty young age.

John


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