Langevin 5116b preamp

[al_p]

Hi

i can't remember who originally posted this schematic, but it was at the old place i think.

http://www.kimaguresound.com/langevin5116b.gif

what is pin 11. it connects those 3 resistors to points XYZ in the cicuit, and is labeled MTR. 'multi track recorder'? meter? monitor? i'm having a hard time figuring out what that is for or does.

hmm. XY balanced output, Z unbalanced output? or way off?

anyone have any ideas on the specs of those thannys?

 

[adrianh]

It is simplier than you thought.
Remember radio gear like that had a meter
for field measurements and circuit balance.
You had a meter connected to this connector and to ground.
Leave it off build your circuit enjoy.

 

[NewYorkDave]

The input transformer is 150:60k, the output is 20kCT:600. I'll check my old Langevin catalog for other relevant specs.

 

[al_p]

thanks guys.

how bout B+ and B-?

B- seems a little unusual to me.

 

[rafafredd]

I think B- is just 0v.

 

[BYacey]

B- is your HV ground. The "ground terminal is just the RF faraday shields between the windings in the transformers. This is not power ground.

 

[al_p]

good. good.

ok so in the grounding scheme the shields get chassis ground and HT 0v is floating? i feel like i would want to ground B-, 0V, power ground to the chassis.

what B+ voltage do you figure 300V?

 

[PRR]

> what is pin 11.

Connect it to a 200uA meter, usually a VU meter, to B-. Push the buttons one at a time. Each one should read near "0VU". Any large difference means a sick tube. Any clear trend over days or months means a dying tube.

For folks with one or two such amplifiers, this is a frill.

I had a Langevin with 28 vacuum tube modules, over 60 tubes, and finding (let alone predicting) a dead tube would be a major headache without a tube-current meter bus like this. You'd squat behind the amp-rack, internal meter to one side, and go down the rows of buttons. For hasty-checks, just be sure they all look about normal. Obsessive shops had a log-sheet and wrote-down the reading for every button every week, so they could track changes and replace a fading tube before it died.

> HT 0v is floating?

Case and HT 0V are tied together ONLY at the power supply. In a 2-amp rack, that's not critical; in a big system it is.

> what B+ voltage do you figure 300V?

IIRC, usually 250V. This is a compromise between output and life. In a large "live on the air" system, low life meant impossible unreliability. In small systems (and current prices on most tubes) you might want to run 300V for a little cleaner sound at the risk of dead-air every few hundred hours.

 

[al_p]

thanks

good info as always PRR

 

[NewYorkDave]

Here's some info from the '61 Langevin catalog that should help to fill in the gaps.

Model AM-5116-B
Power requirements:
Plate: 300VDC
25mA for output power of +24dBM,
12mA for output power of +18dBM (strap removed)
Filament: 6.3V AC or DC at 900mA

Tube check meter: model MTR-506. (No other info given).
Like PRR says, you don't really need this function if you're not running banks of these things.

The B- and the chassis grounds are connected together, all right, but only at one point in the entire system. This is common practice for lowest hum. By way of illustration, here's Langevin's "Recommended Wiring and Grounding Practices" diagram.
Page 1
Page 2

Transformer info:
Input: TF-132-B
Source impedance: 150/600 ohms
Secondary impedance: 60K to push-pull grids
Max level: 0dBM
Electromagnetic shield

Output: TF-129-A
Primary impedance: 20KCT
Secondary impedance: 600/250 ohms
Max level: +26dBM

So, PRR, what became of this old Langevin console of yours? If it was scrapped, I'll cry :roll:

 

[PRR]

> If it was scrapped, I'll cry

I last saw it 28 years ago. It can't possibly still be there: it filled the room and nobody in that place but me could have kept it working. I do cry to think what a milkcrate of those modules and knobs would be worth on eBay today, but who knew? They are long gone, land-fill, like most of these consoles.

FWIW: I was told that this was the console used for TV coverage of Eisenhower's inaugural, and it sure looked that way. I first saw it in a 1950s large motor-home jam-packed with two complete video-tape machines, a hole where a video-switcher was, and this console, with an NBC-TV network logo. The network had donated it to the university where it served a while as a mobile studio and many more years as a parked studio.

But even with a shop full of understanding Hungarian techs (who came to America about the time the van was built), by 1973 the electronics were rough. And the roof had leaked for a whole summer. I was told I could salvage anything, but moving that console (and the servo-amps from the Ampex Quad) nearly killed us. Someone had been stripping mix-transformers so I re-wired it as a simple passive resistive mixer. We used it as our second production board. In hindsight, it sounded better than the "high class" On-Air RCA board (full of 709 chips), though not as clean as the butt-simple low-price discrete-transistor LPB board in the main production studio (that was a honey, except Red and Black were backward).

 

[al_p]

wow. thanks for those Lang docs NYD. they will prove to be very usefull.

anyone have any pics of the innards of a 5116? what is the difference between the 5116 and the 5116b?

 

[emrr]

The 5116 is a single ended amp using two 5879 tubes. Circuit is in the Audio Cyclopedia. It is just about the same as the Collins 356A and the GE 4BA1F1.

The 5116B is a push-pull circuit that came later. I believe it fits the same trays as the 5116.

 

[The Kid]

Holy crap! It took 2 years to find the answer to that question? :grin: :shock: :sam:

 

[emrr]

I just started looking at this forum. Certainly somebody else knew!

 

[The Kid]

Hah! Yeah, I'm sure someone else must've known, I was just amazed at the date gap! That's gotta be a record, for post-resurrection! :grin:

 

[NewYorkDave]

I think the original poster may have just mirrored the schem I posted a while back. I can't find the location of that file right now, but here's a fresh one:

24kB PNG image

 

[emrr]

I've been messing with a few of these AM-5116-B modules this week, and there's some details missing from that schematic. I'm wondering if that's even the official version. Maybe just a simplified version.

The big one: The filaments are strappable at each tube, to allow for 6 or 12 volt wiring. It's not really marked.

C5 doesn't seem to exist in this set.

The high power strap straps out either R13 or R14. Can't tell which yet, for some reason.

R5 and R6 are not easily replaced in a hurry for gain mods, for anyone having that idea with a real module.

Transformer DC resistances are far higher than usual on the input and output, though they match those found on many RCA tube modules.

These have got to be the tiniest similar thing ever made. God help anyone doing repairs on one. Oh, that's me. Replacing that can cap (C6/C7) will be a total bitch. There's no room to do hang-ups or alternate placements of any type. Best solution may really be praying one doesn't break anything during dissassembly, and hollowing out the original can. R5 and R6 actually scrape the bottom of the mounting trays! Yes it's that tight in there! These things were designed to go to the garbage can, rather than be repaired. No other truly pro gear from this era compares in that regard; the cheapest crappiest Gates/Harris stuff is easier to work on.

 

[rafafredd]

I´ve worked on the Electrodyne version, and it´s not that bad... It´s a Langevin licensed version with the same transformers, I don´t know about the caps. There was a really strange cap in there, a dry electrolytic by mallory, two sections, if I recall... Also, I think the high power bypass is the 10k resistor.

Pretty good sounding. Mostly because of the VERY, VERY strange, and high quality langevin transformers.

 

[emrr]

Traditional module type or 'cassette' type'? I've only seen Electrodyne branded AM-201-A's (cassette version), haven't seen any traditional mounting versions with Electrodyne branding. Cassette version looks much easier to service.