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Old 18th January 2016, 04:29 PM   #21
kevinkr is offline kevinkr  United States
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The zero bias valve
The maker of these tubes seems somewhat obscure despite living geographically nearby. I've never even seen one of these tubes and I suspect even back in their heyday they were pretty rare. The maker is listed as an RCA licensee based in Pawtucket RI.

Interesting idea which apparently never really caught on, wondering if cost was excessive or reliability was a problem. It could even be that in the context of depression America there was not a significant market for such a device.
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Old 10th July 2018, 11:39 PM   #22
PRR is offline PRR  United States
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Sorry for the necro.

But the Triad tube building is still there. I-95 (destroyer of many mills) just missed it.

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Originally Posted by kevinkr View Post
The maker of these tubes seems somewhat obscure despite living geographically nearby. I've never even seen one of these tubes and I suspect even back in their heyday they were pretty rare. The maker ... in Pawtucket RI....
It's a mill building. These were built in "bays" of 8'-16' to suit interior framing lumber. In the 2018 pic the back 5-bay building is probably original from mid-1800s. The front 4-bay addition is probably late 1800s. The front two bays, now blank, held the giant tube logo. The rear building in the 1930 etching may be a early 1900s addition now fallen; or may be an artist's conception of how Triad Tubes would grow and expand.

Mills like this are all over the CT-RI-MA piedmont. Big industry for a century. Improved railroads opened-up western competition; by 1929 many had For Sale signs. This one got a taker, many didn't. Leaky roofs doomed many mill buildings. YOU Bostonites know all this; for lurkers.

It's still sturdy enough for yoga.

Get a clipboard and flashlight. Say you are from city hall and have to "inspect the tubes". Look in the the attic, sump, and boiler room, see what got left behind.
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File Type: jpg TriadTubes-2018.jpg (255.2 KB, 224 views)
File Type: jpg TriadTubes-2018-map.jpg (56.4 KB, 237 views)

Last edited by PRR; 10th July 2018 at 11:41 PM.
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Old 11th July 2018, 02:47 AM   #23
smoking-amp is offline smoking-amp  United States
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I've seen a few Triad tubeboxes and tubes in the $1 tube lots I've ordered from ESRC and Vacuumtubes.net. Triad seems to have had some presence in Miami too.

The boxes say the tubes come with a lifetime guarantee! I haven't tried to get any replacements though....
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Last edited by smoking-amp; 11th July 2018 at 02:57 AM.
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Old 11th July 2018, 03:16 AM   #24
PRR is offline PRR  United States
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> presence in Miami too

Rhode Island Radio

In June of 1965 we find an article in The Miami News of The Triad Tube Corporations moving ....Sunshine State Industrial Park in North Dade. ...electronics wholesaler distributing vacuum tubes .... through discount chain stores ....the firms goal to get "at least one per cent of the.... market."
Rhode Island Radio - INDEX

Sometime between 1935-1935 and 1965, the operation (now probably just a warehouse and re-brander) moved from the North to the South.
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Old 11th July 2018, 03:23 AM   #25
smoking-amp is offline smoking-amp  United States
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I would guess that Triad transformers had some connection too. Have seen many Triad power, audio output and TV flyback transformers.
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Old 12th July 2018, 03:21 AM   #26
PRR is offline PRR  United States
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Quote:
Originally Posted by smoking-amp View Post
I would guess that Triad transformers had some connection...
No. Triad Transformers was in/near Los Angeles or Venice from the 1940s until Litton bought the shop in 1957 and Indiana started appearing on the letterhead. More recently they are in California again. (Maybe the iron/factory never left, just different main offices.) As you say, TV made Triad Magnetics BIG.

Triad Historical Archive
Triad Historical Archive
Triad Transformer Catalog 1952

OTOH Triad Tubes appears to have never sold anything but tubes, from RI then Fla, and only in a now-small way. (Their first years they seem to have been "large" for an independent, but the rise of Cunningham Ken-Rad and Harrison doomed all small independents.)

So more like Acme Supermarkets, Acme industrial transformers, and Acme road-runner traps. Just a cool name.
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Old 12th July 2018, 04:56 AM   #27
popilin is offline popilin  Argentina
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Quote:
Originally Posted by PRR View Post
So more like Acme Supermarkets, Acme industrial transformers, and Acme road-runner traps. Just a cool name.
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Old 3rd August 2018, 12:32 AM   #28
gorgon53 is offline gorgon53  Finland
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A pair of zero biased 807 (g1+g2 driven together) can make 120W with 400V on the anodes but need 10W driving power according to some Philips? datasheet

Last edited by gorgon53; 3rd August 2018 at 12:36 AM.
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Old 3rd August 2018, 01:56 PM   #29
Tubelab_com is offline Tubelab_com  United States
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Quote:
Triad seems to have had some presence in Miami too.
In the late 60's I was an avid dumpster diver in and around the Miami Area. This would have been after the move from Hialeah to Miami gardens, so it might have been outside my shopping area, but I don't remember Triad Tubes.

The box in your picture offers a lifetime guarantee, and only states "Miami Florida." Mine all say "Miami Florida 33169" which puts them in Miami Gardens (post 1965). The tubes all appear to be GE's but I only have a few.

Your boxes do not have the zip code. Postal zones became zip codes sometime in the early 60's and weren't often used in addresses. Your tubes may be from the Hialeah area warehouse before the 1965 move.

Many of the discount stores in the Miami area sold a brand called Thoro Test. These could have come from the same place. They were all GE's, allegedly from lots that failed QC and were "thoroughly tested" before branded and sold. I remember the Eagle Army Navy sold Thoro Test tubes for $1 each in the early 70's. Any stocked tube was $1. Guess which tube they couldn't keep in stock because I bought them as soon as they got them in.....yes, shiny new GE 6L6GC's were $1 and I never got a bad one........I might have made a few of them bad...........

It was discussed in the first post of this thread how the 46 tube offered higher efficiency and more power output than the 45 due to its operation in the positive grid region. The 45 will run just fine in AB2 and make about 20 watts per pair. RCA's own data shows near 50% efficiency at 18 watts from a pair of 45's in AB2.

I have seen near 60% efficiency and 24 watts from a pair of 45's at 320 volts on the plates with a 3300 ohm load. Only strong tubes with good emission can do this. Many well used 45's can run fine in a single ended class A amp, but not have the peak emission capability to feed a push pull class AB2 amp. I have not seen 70% real plate efficiency in any tube amplifier, even one running sweep tubes.

I have seen a single pair of old well used 6L6GA's make 100+ watts in conventional class AB2, but attempts to go beyond this level resulted in a non fatal tube arc. I was seriously abusing the poor tubes running somewhere north of 500 volts into a 3300 ohm load when the cathode resistor exploded. The amp played on once I installed a new resistor and kept it under 100 watts.
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Old 3rd August 2018, 03:42 PM   #30
smoking-amp is offline smoking-amp  United States
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Some Beam pentode tubes have plate curve knees that can get down around +40V at lower than max screen voltage. (like 21LG6 or 6LB6 for example) These might approach 70% efficiency in class B. They won't be producing their max rated power with the lowered screen voltage however.

--------------------------------------------------------------

In this link:
Input impedance experimentations, aiming to build an A2 stage

Some speculation on increasing the input impedance of P-P grid current tubes.
If the grid current is near linear with grid voltage (post 3 there), then combining the two grid currents with a CT'd input xfmr, with a suitably tuned CCS on the CT could eliminate most of the drive current required. So greatly increasing the input Z of the driven tubes. Might be applicable to the type 46 tube or an 807, greatly reducing the drive power needed.

Last edited by smoking-amp; 3rd August 2018 at 03:46 PM.
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