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Author Topic: 6MJ6/6LQ6 Black Cap sweep tubes  (Read 1595 times)
K3NRX
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« on: March 05, 2019, 06:54:05 AM »

I ordered 4 RCA Black Cap Sweeps for my amp. Anyone ever use them in an Ameriton AL84? And what is the significance of the “Black Cap?” Does this mAke the tube stronger/more powerful output wise? Or is that just an RCA thing? Tubes tested Two at 200 and the other two at 118. What say u? Good deal???

V
K3NRX
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N8FVJ
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« Reply #1 on: March 05, 2019, 07:07:06 AM »

The tubes have a thick glass. Not sure if plate dissipation is higher than a standard 6LQ6. I do not get 200 vs 110 tube tester readings. The four tubes should be close to one another. Perhaps you received two half dead tubes?
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K3NRX
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« Reply #2 on: March 05, 2019, 07:15:35 AM »

Sorry, meant to say two tested at 120 and the other two at 118. Dyslexia  Roll Eyes

V
K3NRX
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N8FVJ
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« Reply #3 on: March 07, 2019, 04:53:03 AM »

Good test figures. And, I knew of no testers that went above 130 anyways. Use the tubes.
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K4QM
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« Reply #4 on: March 07, 2019, 06:41:52 AM »

I ordered 4 RCA Black Cap Sweeps for my amp. Anyone ever use them in an Ameriton AL84? And what is the significance of the “Black Cap?” Does this mAke the tube stronger/more powerful output wise? Or is that just an RCA thing? Tubes tested Two at 200 and the other two at 118. What say u? Good deal???

V
K3NRX

What does all that mean?  I see tubes listed with dark plates, round, oval getters.  All that does NOT mean a darn thing.  Not too sure
that the guy running the add thinks either.  Something else to justify the high price they ask for the tubes.  Even a number they sue to indicate
a tube test.  "tested on a Hickok tester doesn't mean anything either.  I look at the tube adds and have a good laugh.
Clayton K4QM
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W2NO
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« Reply #5 on: March 07, 2019, 04:04:34 PM »

A regular 6LQ6 will have a wire out of the top envelope of the glass with a metal cap soldered on it for the Anode connection. The "Black Cap" ones you speak of have a heavy black post with a Kovar seal for the Anode. Not sure what the difference is, could have been special order for a Contract job. I have been in the electronics industry for 40+ years and have never seen one in person.

Dan. W2NO
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K9AXN
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« Reply #6 on: March 07, 2019, 04:34:54 PM »

The 6MJ6 is a direct replacement for the 6LQ6.  The 6MJ6 was developed specially for the SSB community.

It has the same plate dissipation, BUT it will tolerate 200 watts of plate dissipation for 40 seconds --- enough time to load the amplifier.  I believe the glass is thicker like the Matsushita S2001A.

Regards Jim
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K3NRX
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« Reply #7 on: March 12, 2019, 08:49:01 AM »

Tubes arrived in great shape and are in the amp....I am able to kick out a solid 400w output, as I try to not drive it too hard with the rig....about 75-80 watts of drive seems to be enough to keep the meter on the amp from going beyond .8ip...I was hoping to get a bit more out of them, but what I have is enough with in the realm of not burning things up.....it was time to replace those old tubes....they had lost their mojo....this was worth the money.....now if only the damn conditions would improve....

V
K3NRX

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N8FVJ
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« Reply #8 on: March 12, 2019, 05:08:44 PM »

Your tubes are in the old tube TV high voltage rectifier tube glass and black cap. The glass is twice as thick as the standard 6LQ6.
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K3NRX
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« Reply #9 on: March 13, 2019, 08:56:19 AM »

Your tubes are in the old tube TV high voltage rectifier tube glass and black cap. The glass is twice as thick as the standard 6LQ6.

and that's a good thing, I presume...Thanks...

V
K3NRX

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WB0SND
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« Reply #10 on: July 05, 2019, 10:51:55 PM »

The difference between a 6MJ6 and 6LQ6 is that the 6MJ6 has leaded glass to reduce X-ray radiation.  The plate connection was made that way due to the leaded glass.  If you look at any of the late production TV tubes like 6BK4C, etc. they all have lead in the glass and similar plate connections.  The 6MJ6 has no more ability to handle power than a 6LQ6.  That is a misnomer.  Look in the tube handbooks.  The plate dissipation is the SAME
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KM1H
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« Reply #11 on: July 06, 2019, 02:20:07 PM »

The difference between a 6MJ6 and 6LQ6 is that the 6MJ6 has leaded glass to reduce X-ray radiation.  The plate connection was made that way due to the leaded glass.  If you look at any of the late production TV tubes like 6BK4C, etc. they all have lead in the glass and similar plate connections.  The 6MJ6 has no more ability to handle power than a 6LQ6.  That is a misnomer.  Look in the tube handbooks.  The plate dissipation is the SAME

Im glad that someone who knows what he is talking a about spoke up and those became the 6LQ6/6MJ6 on into the sunset.

Carl
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G3RZP
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« Reply #12 on: July 06, 2019, 03:56:36 PM »

Carl,

Wasn't the 'Nonex'  used in the 35T and 35 TG (and some other Eimac tubes with tantalum plates) a leaded glass? It had a vaguely green tinge to it... I know that a 35T at full ratings had a white hot plate through which you could see the shadow of the grid wires, illuminated by the filament.....
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KM1H
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« Reply #13 on: July 06, 2019, 05:39:39 PM »

Carl,

Wasn't the 'Nonex'  used in the 35T and 35 TG (and some other Eimac tubes with tantalum plates) a leaded glass? It had a vaguely green tinge to it... I know that a 35T at full ratings had a white hot plate through which you could see the shadow of the grid wires, illuminated by the filament.....

The 152TH/TL and 304TH/TL had that as did the VT-127A (100TH variant for radar use) and its variants I believe.I dont know about the small versions. Many mistakenly called it uranium glass.

The 152TH/TL was a pair of 75TH/TL's in one envelope and the 304 was 4 that could be operated as two or 4. My avatar on QRZ has a pair of 304TL's running all 4 somewhat modestly Roll Eyes

Carl
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