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Author Topic: 6146??? 6146B - w  (Read 8900 times)
KB2WVO
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Posts: 382




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« Reply #30 on: September 29, 2017, 04:16:07 PM »

6146 series of tubes are very sensitive to gird current.  I love the them but have destroy several by over driving the grid.  I no longer use them for that reason.  I seem to remember 2 ma would give full output on CW.

Stan ak0b

what do you use in place of them?

and the radio is very hard to set... seems only about 80 to 90 watts out. so more to read in manual and check. it is a heathkit sb110. manual says check this n that for voltages. they seem on. 105 volt range. doing what the build manual says. thats the highest i can get the voltage. yet it doesnt say if 105 volts is good or not..

this is off the drive tube i think. spot 2 on the plug. if anyone reading knows heathkits.. the 100ohm removed. from the thru cap to the one 6146.

anyone who knows the rite way and more so then manuals. hints tips tricks? votlages so on..
not a lot of videos on the old girl ..
« Last Edit: September 29, 2017, 04:20:44 PM by KB2WVO » Logged
KB2WVO
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Posts: 382




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« Reply #31 on: September 29, 2017, 10:45:01 PM »

wow only .3 on the swr and the radio WOKE up.. full 100 watts..
from a 1.5 on 50.125 to a 1.2 and its barking out 100 watts...

touchy old girl she is... but i love it ...

so i must be learning from the great folks out here a little something..
ty all for the help..

cold , hot or BOG to all.. 
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K1DA
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Posts: 723




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« Reply #32 on: November 21, 2017, 05:45:24 PM »

Glen Zook wrote a fine article called "The 6146 family of tubes" which can be found by Google.   In some radios, like the early S lines the "B" is not a direct replacement.
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WA4JQS
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Posts: 78




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« Reply #33 on: November 22, 2017, 01:16:37 PM »

YES  the read write up from Glen. Glen and I talked about this years ago. a lot of old tube radios would not let you do a direct replacement from 6146-/A to the B tube line. the W ruggizied  tubes caused problems in a few of the rigs. Collins rigs were picky if i recall. I had trouble running B's in one of my rigs can not recall if it was the HW 100 or the Swan 250C . there was a lot of talk about this back 25 years ago.
73 Tony WA4JQS / V31SS
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KOP
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Posts: 245




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« Reply #34 on: November 22, 2017, 09:06:37 PM »

https://frrl.files.wordpress.com/2008/08/6146tubefamily.pdf
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October 02, 2017, 07:53:41 PM
WA5VGO
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Posts: 38




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« Reply #35 on: November 23, 2017, 08:13:32 AM »

This is nothing but urban myth. The 6146B is an exact replacement for 6146 and 6146A. Just take a look at the RCA spec. sheet. Are you going to believe RCA or a internet rumor? I’ve put 6146B’s in dozens of radios that originally had 6146’s. Every one of them worked flawlessly. I’m referring to US manufactured tubes. In the case of off-shore tubes, all bets are off.

http://www.mif.pg.gda.pl/homepages/frank/sheets/079/6/6146B.pdf

By the way, my HW-100 came from Heathkit supplied with 6146B’s.

« Last Edit: November 23, 2017, 08:32:12 AM by WA5VGO » Logged
KOP
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Posts: 245




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« Reply #36 on: November 23, 2017, 08:52:18 AM »

B's in my HW-101, TS-830, Tempo 2020.
      In each case neutralization is important. I've only had one issue with an old tube in the TS-830 when the screen laid over with the predictable screen and cathode resistor failures along with the plate choke up in smoke. This would have happened regardless of what tube variation it was. I've actually never used anything but B's in these radios so I don't  have an idea what the difference would be. 
       I have read about the differences extensively and since I have a glut of B's it's what I use.
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October 02, 2017, 07:53:41 PM
K9AXN
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Posts: 347


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« Reply #37 on: November 24, 2017, 09:10:32 AM »

Read the entire tube data sheet for the 6146 and 6146B paying special attention to the operating range of values.  Glen was right --- they are not the same tube but the B version will usually work as a replacement in most radios --- BUT NOT ALL.

When RCA designed the B model, it was to compete with the growing popularity of Sweep tubes used in class AB1 radios.

The precision alignment of the control and screen grids are slightly off in he B model requiring the idle bias of the tube to be increased.  This enables the leveraged increase in output when running AB1 mode.

Net result, if the radio has a wide enough range of bias and neutralizing adjustments --- no problem; provided the operator actually understands neutralizing requirements and techniques.  There are as many techniques as Ham radio folks --- most are SWAG.

Have a great day ----  Regards Jim     




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WA5VGO
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Posts: 38




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« Reply #38 on: November 24, 2017, 02:24:11 PM »

"The 6146B/8298A is unilaterally interchangeable with the 6146, 6146A and 8298."

That sounds pretty definite to me.
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K9AXN
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« Reply #39 on: November 24, 2017, 07:00:37 PM »

"The 6146B/8298A is unilaterally interchangeable with the 6146, 6146A and 8298."

That sounds pretty definite to me.

You read that in the 6146B romance sheet --- who wrote that statement?  Did you read the range of operating parameters? 

I won't repeat the litany of damage reports involving the use of the 6146B in radios that are not designed to use them.  Have you ever heard anyone suggest mixing the 6146B with a 6146 --- that to sounds pretty definite and contradictory to "The 6146B/8298A is unilaterally interchangeable with the 6146, 6146A and 8298".

Have a great day.

Regards Jim 
   
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VK6HP
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Posts: 184




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« Reply #40 on: November 25, 2017, 12:56:14 AM »

It may be that there's an element of myth around the topic but it's also clear, if only from the Collins experience, that a tier-1 radio company's line required well-documented and widely implemented modifications to make the 'B' tubes backwards compatible in early serial number radios.  I think there probably is almost "unilateral" compatibility, but it's in the direction of A --> B, not the other direction, regardless of any marketing hype of the day.  That of course assumes the "A" tubes are then operated within their limits.

Perhaps of more contemporary interest is where some of the currently available variants sit on the compatibility list.  For example, I've long wondered about some of the central European vendors advertising Siemens QE 05/40 tubes.  I eventually tracked down some probably applicable German data sheets and it looks to me as if the advertised tubes might be closer to an "A" than a "B" variant, despite one reputable advertiser's by-line.  When queried he acknowledged that this might be the case but, probably correctly, noted he'd had no complaints when the tubes were used in e.g. the Kenwood hybrids.  Maybe it's another example of essentially 6146A-->B compatibility, with power limits respected.  Perhaps some European readers might have more direct knowledge of the 05/40 claims - were they ever advertised as a direct 6146B equivalent?

I'd be very interested to hear of any experiences with the Siemens tubes, particularly in terms of neutralization and sustainable power output.  Until now I've collected NOS RCA or similar but they are getting rarer and the German tubes look more plentiful.  

73, Peter.

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G3RZP
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Posts: 8141




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« Reply #41 on: November 25, 2017, 02:17:54 AM »

Other than matching tubes or separate bias adjustments for each or just ignoring the problem, what is suggested for the 2:1 range of plate current between tubes possible at fixed bias?

see: http://frank.pocnet.net/sheets/079/6/6146B.pdf on then bottom right of page 3.

This range is much the same for all the 6146 family.
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VK6HP
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Posts: 184




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« Reply #42 on: November 25, 2017, 03:19:23 AM »

Well, those are all valid coping mechanisms Smiley  I guess you could add choice of a circuit topology where matching is somewhat less critical, such as parallel rather than push-pull.  I must say that I have not personally observed anything like a 100% anode current variation across known good tubes. In practice, my starting point is to pick a pair of tubes of the same internal construction and which are sensibly close on a quick tube tester run.  I then run them individually in my "spare" TS-830S and check that the bias values and anode currents are OK.  With that done, I've never had a practical issue in achieving good to very good IMD figures in my Kenwood and Collins gear, both of which use parallel PA stages with local feedback.

A few weeks ago my "good" TS-830S started getting very hot in the PA area and, eventually, blew the mains fuse.  It turned out that one of the RCA 6146Bs had decided to let the side down badly and leave the very great fraction of the work to its partner.  I'm sure the single hard-working tube wasn't the greatest in IMD terms but, while I didn't bother to connect the spectrum analyser at that time, the output was certainly not horrible.

The replacement tubes are again RCA types but I'm now down to 1 spare set of those, hence the interest in the 05/40s.
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G3RZP
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« Reply #43 on: November 25, 2017, 04:02:38 AM »

When I get around to doing it, I'm going down the separate bias pot route for each valve, especially as the FT102 has three of them. My remaining other 13 valves show a 2:1 variation between them. Fortunately, at one time, I had a practically limitless supply of 6146Bs.......
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KM1H
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« Reply #44 on: November 26, 2017, 03:25:46 PM »

Ive mixed around most of the 6146 family and the Kenwood supplied Japanese S2001 in TS-830's without anything more involved than a neutralization tweak.

I do run them at 100W, and not balls to the wall like a CBer, and the IMD is more than reasonable.

The hybrids are notorious for the carbon composition resistors in the cathode and screen circuits becoming way out of spec, something the general tube swapper does not realize.

Carl
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