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FT101 6JS6C to 6146 conversion advice please

閲覧: 27 回
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Dave Bullock

未読、
2002/12/03 2:45:522002/12/03
To:
I have recently aquired an FT101 less output finals, and I am
considering converting it to 6146's.
I have the ZS1J (QST) article on how to do this but am a little
concerned about the voltages vs valve ratings.
Also which suffix of the 6146 to go for.(straight 6146, or A,B or W).

I have 6146W's readily available in matched pairs so was considering these.
FT101 seems to have around 700Vdc plate voltage and 160V screen supply.
(I haven't meaured what it 'droops' to, on load)
Also the ZS1J article recommends that the screen connection be removed
from the 160v point and be connected to the 300V driver stage supply.

The data (for all 6146 suffixes, A,B&W) states that for ICAS use, the
maxumum plate voltage is 750V at a screen voltage of 160V! So why does
ZS1J connect it to 300v? The datasheets also state that the screen
should be fed through a resistor of between 40-56K ohms, the FT101 seems
to only have 100 Ohms!

Has anyone carried out this modification successfully, or have any
technical insight that would be useful? I would appreciate your comments.

Thanks in anticipation.....Dave
--
* * * * * * * * * * * * * * * * * * * *
* Dave Bullock *
* MRC Institute of Hearing Research *
* Nottingham University *
* Nottingham *
* NG7 2RD *
* *
* da...@ihr.mrc.ac.uk *
* * * * * * * * * * * * * * * * * * * *

mke...@powerup.com.au

未読、
2002/12/03 6:58:232002/12/03
To:
The 'W' is a stronger envelope only - the 'B' has more dissipation.
I used 300 on the screens at abt. 900v on the plate.
The Radio Inspector put it on his analyser and pronouced it
'fine'. It was emitting 180W PEP.

It had the 'B' tubes.

Cheers.
Murray

--
******************************************************************
* Murray Kelly vk4aok mailto://mke...@powerup.com.au *
******************************************************************

Mark Keith

未読、
2002/12/07 5:55:462002/12/07
To:
"mke...@powerup.com.au" <mke...@powerup.com.au> wrote in message news:<3DEC9C5F...@powerup.com.au>...

> The 'W' is a stronger envelope only - the 'B' has more dissipation.
> I used 300 on the screens at abt. 900v on the plate.
> The Radio Inspector put it on his analyser and pronouced it
> 'fine'. It was emitting 180W PEP.
>
> It had the 'B' tubes.
>
> Cheers.
> Murray

Hummm. I was always curious what the exact difference between a "W"
and a "B" was. I thought the W was a military version with the same
appx specs as a "B". I was under the impression that they both had the
same 35 watt plate dissipation. I know the "B" was 35 watts, with the
old "A" 6146 having 25 watts dissipation. If the "W" is lower, what is
the dissipation? I do notice most "B"'s seem to cost more...The 6146
was probably the best power tube made for that size tube. Much harder
to kill than most sweep tubes. Drake 6JB6's in particular don't hold
up to abuse with their puny 17 watt dissipation. I used to eat a set a
year, back when I ran drake twins non stop. MK

http://web.wt.net/~nm5k/

N2EY

未読、
2002/12/07 9:09:242002/12/07
To:
In article <25eb70d7.02120...@posting.google.com>, nm...@wt.net (Mark
Keith) writes:

>"mke...@powerup.com.au" <mke...@powerup.com.au> wrote in message
>news:<3DEC9C5F...@powerup.com.au>...
>> The 'W' is a stronger envelope only - the 'B' has more dissipation.
>> I used 300 on the screens at abt. 900v on the plate.
>> The Radio Inspector put it on his analyser and pronouced it
>> 'fine'. It was emitting 180W PEP.
>>
>> It had the 'B' tubes.
>>
>> Cheers.
>> Murray
>
>Hummm. I was always curious what the exact difference between a "W"
>and a "B" was. I thought the W was a military version with the same
>appx specs as a "B". I was under the impression that they both had the
>same 35 watt plate dissipation. I know the "B" was 35 watts, with the
>old "A" 6146 having 25 watts dissipation. If the "W" is lower, what is
>the dissipation? I do notice most "B"'s seem to cost more...

"W"s are just ruggedized "A"s. The "B" is different enough that it
interchangeability is an issue. Some rigs can use Bs and some can't. Others
require adjustments like reneutralization or even minor circuit modifications.,


>The 6146
>was probably the best power tube made for that size tube. Much harder
>to kill than most sweep tubes. Drake 6JB6's in particular don't hold
>up to abuse with their puny 17 watt dissipation. I used to eat a set a
>year, back when I ran drake twins non stop.

I think the main reason Drake and others used sweep tubes was that, in their
time, they were less expensive and more easily available than 6146s! How times
change...

73 de Jim, N2EY
>


Gary Schafer

未読、
2002/12/07 15:44:512002/12/07
To:
The W supposedly had a more rugged filament. The 6146W can be a
regular 6146 type or it
can be a 6146B type depending on when it was made. Supposedly the
later W versions were
the same as the 6146B as far as electrical specs. The B came out some
time in 1964 but the W
did not adopt it immediately but some time after that. So if you have
W's after 66 or 67?? they
may be the same as the B.

As far as running high values of resistance in the screens, that will
raise IM. Also higher that
specked screen voltage will raise IM products. They should be run at
manufacturers spec on the
screens with a stiff supply.

73
Gary K4FMX

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