Dump Find of The Day

[EWBrown]

It doesn't happen too often around here, but I got "kissed by Lady Luck", and found a very clean condition Rauland-Borg PA amp at the dump today.

The first thing I saw inside was a pair of Mullard 7189s, plus an RCA 6CA4, a 12AX7A and 6AV6. Nice and clean, no corrosion, mouse whizz or dead critters inside,
just a little light dust, which is to be expected - otherwise, it looks almost brand new. There is a date stamped on the underside of the OPT, June 1967.
Made in USA, Chicago, Illinois. The PT and OPT are horizontal-mount, end bell on the top, and open on the underside.

Took off the cover and bottom plate, which look as if they had never been removed before, and what I can see inside is a fairly standard fixed-bias, PP circuit,
I'll have to trace out the circuitry, and draw up a schematic. There is also an octal socket for an optional relay which would be used to allow the microphone PTT to
over-ride the music / phono input(s). It also has a very simple single pot mixer / fader control for the two "aux" RCA inputs. And a single "tone" control and a
"master" volume pot.

As it appears, it looks like the perfect basis for a conversion to an "18 watt" guitar amplifier. If I were to decide to add a tone stack and reverb, that would require
another tube socket or two, no problem, there is still plenty of room on, and under, the chassis. Not at all crowded.

Before all that ever happens, I'll have to check it out, then carefully power it up on a variac, and make sure that no "magic smoke" escapes, the quad section can cap doesn't go BOOM! and that no strange aromas emanate from within...

The other two (lesser) finds were a recent model Ford AM/FM/CD Radio, which was most likely removed for a "Crutchfield Update", and a small 24VDC,
400 mA power supply.

I did a quick web search for "Rauland-Borg", the company still exists, it has relocated to Florida, and seems to specialize in security and audio distribution systems,
probably none of which involve the use of vacuum tubes...


WARNING!!!! Full Tubal Nudity!







Everything seems to work, a tiny bit of hum, but then, that's with the bottom and top covers off.
7189s run with B+ approx 390VDC, G2s approx 370VDC, G1 bias -16VDC.
I have the circuit partially traced out, only "unusual" thing is the extra NFB secondary winding, and that feeds into the PI grid as well as the
12AX7 cathode in the preamp stage, through a three-section resistive divider.

/ed B

[nyazzip]

ah, some Chicago history....

"Rauland-Borg's roots are in the founding, in 1922, of the Rauland Company by inventor and radio enthusiast E. Norman Rauland. In 1924, he became a pioneer in the radio broadcast industry by launching his own, Chicago-based radio station, WENR. Throughout the Depression, Rauland manufactured power amplifiers and equipment for public address systems. During this time, the Rauland Company won government contracts to produce radio and communication systems for the military.

In 1941 Norm Rauland and George Borg entered a partnership that would change the history of the company forever. The Rauland Corporation acquired the Webster-Chicago Corporation, a leader in school communications, and Rauland became firmly established as the dominant supplier of internal school communications systems.


In 1942, the Rauland Corporation acquired Baird Television of America. Rauland began developing the cathode ray tube (CRT), and as a result, the company became an important supplier of communications and radar equipment during WWII. After WWII, the Rauland Corporation began manufacturing CRTs for 10 and 12 inch televisions.

In 1948, two major events happened. First, Zenith Radio Corporation purchased the Rauland Corporation to acquire the CRT business. Second, Norm Rauland and George Borg started a new company, Rauland-Borg Corporation, for continuing the sound and communications business. As the company further developed its commercial and industrial communications components, they remained an important military contractor providing such essential products as the Navy's ship-to-shore radios, airborne radar jamming transmitters, walkie-talkies, classified cryptographic switching adapters, tank radios, intercom systems and radios for arctic regions.

In the early 1960s, the use of transistors was still limited but Rauland-Borg demonstrated its technological leadership by transforming its entire line of sound and communications products to transistorized and solid state components. Recognizing the need to keep school instructors and staff in touch with each other, Rauland-Borg introduced the first generation of Telecenter® products in 1968. Telecenter® was the first-ever commercial application of touch-tone technology which has since become the backbone of school communications, worldwide.

In 1979, after the acquisition of the Picker-Briggs Company, the prestigious manufacturer of the Responder® health care communications systems, Rauland-Borg established itself as a leader in nurse call communications.

In 1989, Rauland-Borg acquired Biamp Systems Company, a long-time designer and manufacturer of Biamp® professional audio equipment. In the 90s, the company expanded its existing product lines into Latin America and the Pacific Rim."

[soundbrigade]

May I "kidnap" this thread a little.
We have a discussion in our Swedish Electronics Forum about the coolest (or hottest) radio tube in our collections and I remember the vibrationtester at RIFA that was powered by some megalitic supertubes - THAT was a real sub amp!!!! Got through to a friend and old collegue at RIFA who was servicing the machine from time to time and was also sent pics - will fix them for the Soik Nail-thread - and some other info from him.
My friend had salvaged a huge number of tubes that was part of controller devices for cannons. The tubes were all Swedish made and mechanically extremely durable and stable, all approx equivalent to 6SL7. He also had some Swedish version of 6V6.

Have a look at the pix - http://sm7ucz.se/Kanongrej/Kanongrej.htm (use Google translate to get the text).

Pix from the classroom: http://sm7ucz.se/KRAS/2012.htm

[DerekVa]

Good looking iron, Mullard 7189s and Cinch sockets. What's not to like!?

-D