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 Post subject: 1619 substitute for '45?
PostPosted: Apr Mon 09, 2007 4:19 am 
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Joined: Dec Sat 30, 2006 9:03 pm
Posts: 243
Location: Melrose, NY
This evening I got a look at my son-in-law's Majestic (Grisby-
Grunow) model 90. The output tubes looked odd, so I pulled
one, and it turned out to be a 1619 (VT-164). The internet
says that the 1619 is a 2.5 volt 6L6. The schematic specifies
push pull '45's. I'm suspicious that someone rewired the 1619 as a triode, but I don't dare pull the chasis, he'd be after me with the
weapon of his choice.

Has anyone seen this modification?

Don, WA2YQY@cs.com


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 Post subject:
PostPosted: Apr Mon 09, 2007 5:05 am 
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Location: Detroit, MI USA
Yes, that's a very common and apparently also a good substitution. It goes back many years. The 1619 is a nearly perfect sub for the 45 tube, only the filament current is higher. On a set with 2.5 volt tubes, they draw quite a bit of current anyway and the use of the 1619 doesn't cause any problems. It's a reasonable and inexpensive way to sub for $$$ 45 tubes.

There are even commercially sold adapters to use the 1619 in place of the 45 for those who don't want to construct their own or replace the sockets.

You are correct, the 1619 is wired as a triode when using as a sub for the 45. The only possible issue is difference in bias voltages, but a circuit using the 45 is nearly always already biased considerably more than the 1619 requires.

You can leave the set alone, and enjoy it.

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Experience is what you gain when the results aren't what you were expecting.


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 Post subject:
PostPosted: Apr Mon 09, 2007 5:32 am 
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Joined: Dec Sat 30, 2006 9:03 pm
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Location: Melrose, NY
Thanks, Dennis...

Now that I think about it, the tube socket was a ceramic, with
gaps around it. Most likely a replacement.

Another item to add to my bag of tricks!

Don, WA2YQY@cs.com


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 Post subject:
PostPosted: Apr Mon 09, 2007 6:52 am 
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Location: Rochester, NY USA
It's pretty easy to make an adaptor using an old 4 pin tube base and an octal socket. Here's a shot showing a 1619 in such an adaptor along with original globe and ST type 45s.
Image
The 1619 sub is good to use in a radio run as a "daily driver" so that the original 45s can be preserved if you ever want to display it.

David


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 Post subject:
PostPosted: Apr Mon 09, 2007 12:06 pm 
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Location: Warren, MI, USA 48093-6744 N42.50973 W83.02633
I've had a 1619 kicking around here for some time, never did get to use it yet. But I found some more for $1 each at the TMRA swap, so I have four of them now.

Saturday, I got around to testing them. I tested them as 45s (just changed the switches to make different pins active - my tube tester does not show settings for a 1619), but had to back the settings down somewhat, it seems the transconductance of a triode connected 1619 is higher than a 45.

I would go with the adapter like ddk375 showed, but it sounds to me like someone already changed the sockets.

Now what I wonder is, we'd use the adapter so as not to butcher the original sockets. If someone changed the sockets (so it is pre-butchered), could someone wire them as pentodes, I.E. connect the screen grid to one of the B+ points?


The description of the 1619 says:

Coated-filament type having metal shell used as af power amplifier and modulator and as rf power amplifier and oscillator. May be used with full input to 45 MHz. For operation at 60 MHz, plate voltage and plate input should be reduced to 90 per cent of maximum ratings; at 90 MHz, to 77 per cent. Requires octal socket and may be operated in vertical position only, base up or down.Base similar to 7AC except no cathode.

------------------
7AC basing has G3 & cathode connected to pin 8. Is pin 8 used for G3 only?

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 Post subject:
PostPosted: Apr Mon 09, 2007 2:41 pm 
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Location: Livermore, CA
Hi

Notice Dennis mentioned biasing. A circuit designed for a 45 will be over biased with a triode connected 1619. This tube can be used as a 45 with higher gain but less output power. Using 1619's a radio will distort if volume is turned up very loud.

Another thing to think about is filament current. A 1619 draws 2 amps while 45 draws 1.5 amps. This might be a problem in radios with small power transformers?

Don

Some tube manuals show 1619 as a 2.5 volt 6L6. This is an error in tube manuals. A 1619 is actually a filament type tube rather than cathode/heater type like 6L6.

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 Post subject:
PostPosted: Apr Mon 09, 2007 8:01 pm 
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Location: Portland Oregon
I was trying to find the specs on the 1619 tube but I cant seem to find it in any of my tube manuals. Is there a place on the web I can find it?
Ed


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 Post subject:
PostPosted: Apr Mon 09, 2007 8:42 pm 
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Location: Livermore, CA
Hi Ed

It's here:

http://www.mif.pg.gda.pl/homepages/fran ... 1/1619.pdf

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 Post subject:
PostPosted: Apr Mon 09, 2007 9:36 pm 
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Location: Detroit, MI USA
Others have mentioned connecting G1 and G2 together to lower transconductance and gain more closely approximating that of the 45.

I haven't run into any cases where you could stand to turn the volume up high enough to get into the region of distortion caused by having too much negative bias. I have used 1619's in Philcos, Majestics, and other sets, they worked fine in all of them. If you put the completed adapter with 1619 in a tube tester and test it as a 45 it checks very nearly the same.

However, it is a very simple matter to add resistance inside the adapter to reduce the bias to whatever voltage is desired if one chooses to do so. A couple of 100 ohm 1% 1 watt resistors in series across the filament pins will give an effective balanced CT connection for one end of a resistor connected to G1. Value of that resistor selected based upon existing G1 circuit resistance and voltage to give desired bias. I see no reason to bother changing the bias unless the substitution doesn't sound good in a particular radio, and I'd make certain the set worked properly with a 45 before making any bias changes.

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Experience is what you gain when the results aren't what you were expecting.


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 Post subject:
PostPosted: Apr Mon 09, 2007 10:16 pm 
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Location: York, PA USA
I guess I'll have to start rolling these. I now have 6 radios with push/pull 45's. How much do the 1619's go for and who has the best deal on them? Bill Turner has the completed ones on his website for $20 shipped. Probably a good deal since a 4 tube plug and an octal socket would have to be bought.

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 Post subject:
PostPosted: Apr Mon 09, 2007 10:20 pm 
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Location: seabeck,wa. usa
Don't forget the other possibility of using an adapted 5A6 in place of a 45, as suggested by Norm Leal. Have a pair in a Philco and they seem to do fine.


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 Post subject:
PostPosted: Apr Tue 10, 2007 12:59 am 
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Don't tell the Audiofools about these 1619 and 5A6 tubes, or they'll skyrocket in price!! :wink:

Jerry


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 Post subject:
PostPosted: Apr Tue 10, 2007 12:43 pm 
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JeepsOLot wrote:
Don't tell the Audiofools about these 1619 and 5A6 tubes, or they'll skyrocket in price!! :wink:

Jerry


I don't *think* the audiofools would be interested. Those are both beam power pentodes, and their thing is for single-ended triodes. Even if you triode connect them, they are still pentodes. A pig in a suit is still a pig.

Besides, they are still relatively cheap, and they don't have the "snob appeal" that things like 10s, 50s, and 300Bs have.

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 Post subject:
PostPosted: Apr Wed 11, 2007 1:25 am 
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There was quite a detailed description of the adaptor and such a year or so back. Try checking back in the archives.
I nailed 24 more of the 1619's for adapting, as I bought 28 radios that all the 45's had been removed from.

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 Post subject:
PostPosted: Apr Wed 11, 2007 1:44 am 
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JeepsOLot wrote:
Don't tell the Audiofools about these 1619 and 5A6 tubes, or they'll skyrocket in price!! :wink:

Jerry


Please Jerry, lets get the spelling correct, "Audiophool". Let us not bestow the proper dignity...

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 Post subject:
PostPosted: Apr Wed 11, 2007 3:32 am 
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Pardon me, Don, :wink: AudioPHools it is! :D

Jerry


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 Post subject:
PostPosted: Apr Wed 11, 2007 5:21 pm 
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Posts: 1863
Location: Houston Texas USA
Don, Huggy, et al...

Some interesting information, fellow Members...And while I am familiar with the practice of transforming multi-grid power tubes to perform as a triode-substitutes in both AF and RF amplifier circuits, the conversion scheme put forth for the 1619 is the first one I had read about.

>"I don't *think* the audiofools would be interested. Those are both beam power pentodes, and their thing is for single-ended triodes. Even if you triode connect them, they are still pentodes. A pig in a suit is still a pig."< -- Huggy

While your second and third sentence is certainly true, don't underestimate the adventurism of the audio amplifier experimenter, homebrew enthusiast and "high end" esoteric tube audio amplifier cottage industry here in North America and abroad...No tube, radio receiving or transmitting type, is "safe" from the clutches of audio enthusiasts (or 'phools)...This situation is not totally new to the scene...There is a somewhat long history involving some tubes such as the beam power 807 that have been incorporated in P-P audio amplifier output stages...And while that may be easy to understand given its 6L6 lineage, there are others as well.

Some time ago I couldn't understand why a modest supply of 1626 tubes I had for sale--used in the ARC-5 and Command Set transmitters from WWII--were commanding such high prices on eBay...Two minutes research revealed a "bump" in interest for this tube among audio enthusiasts in far away places...There are other examples, as well, including some commercially produced audio gear by the aforementioned "cottage" builders employing the 833 or other transmitting tubes that sell for prices clearly in the upper reaches of the stratosphere.

Here is a listing of tubes I found via a Google search awhile back...You can see before your very eyes what I'm referring to with regard to those tubes (triodes, tetrodes, pentodes and beam power types) such as the highly prized 45 found in vintage radio gear...Other on-line sources of information, including a number of tube vendors have information or links to information about the application of vintage and latter-day radio tubes in audio amplifier and pre-amplifier circuits for the music (guitar) and/or high fidelity enthusiast...This awareness and the chit-chat that is found in audio publications, forums and message boards only fuels the renaissance of tube audio gear and the growing interest and demand for tubes of all types.

http://www.webace.com.au/~electron/tubes/Audio.htm

FWIW

Bruce
WC5CW


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 Post subject:
PostPosted: Apr Wed 11, 2007 5:30 pm 
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Location: Livermore, CA
Interesting how they seem to think voltage is the best way to classify output tubes.

1626 is a nice low gain triode. Didn't think the were that popular having a 12 volt filament. I use them to replace some Arcturus 15 volt filament AC tubes.

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 Post subject:
PostPosted: Apr Wed 11, 2007 9:46 pm 
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Location: Pocasset, Cape Cod, MA
Well there aren't that many triodes to choose from. Once the 50, 10, 45. 2A3 and so on had been "discovered", the 1626 was a natural, and at first was available cheaply.

Not to worry about the metal tubes ever being vacuumed up by audiophools. If you can't see the glow, there's no magic.


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 Post subject:
PostPosted: Apr Thu 12, 2007 1:55 pm 
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Location: Rochester, NY USA
1626 has a distinguished audio history - as I recall, it was used in some of the early Heathkit amps. Heath must have made a real deal on some military surplus tubes!

David


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