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  #1  
Old July 9th 19, 07:05 AM posted to rec.audio.tubes
Paul James
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Default 171a

Does anyone here have any experience with using 171a in a linestage. Thinking of using constant current.
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  #2  
Old July 9th 19, 01:23 PM posted to rec.audio.tubes
Peter Wieck[_2_]
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Posts: 99
Default 171a

On Tuesday, July 9, 2019 at 2:05:49 AM UTC-4, Paul James wrote:
> Does anyone here have any experience with using 171a in a linestage. Thinking of using constant current.


The 71A is a low-gain DHT that is valued and prized by the Vintage Radio community. You in the Audio Community have multiple options for this purpose that do not suck resources from your cousin. Who have, too often, no viable alternatives.

Peter Wieck
Melrose Park, PA
  #3  
Old July 16th 19, 02:14 AM posted to rec.audio.tubes
buffstereo
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Posts: 3
Default 171a

On Tuesday, July 9, 2019 at 5:23:18 AM UTC-7, Peter Wieck wrote:
> On Tuesday, July 9, 2019 at 2:05:49 AM UTC-4, Paul James wrote:
> > Does anyone here have any experience with using 171a in a linestage. Thinking of using constant current.

>
> The 71A is a low-gain DHT that is valued and prized by the Vintage Radio community. You in the Audio Community have multiple options for this purpose that do not suck resources from your cousin. Who have, too often, no viable alternatives.
>
> Peter Wieck
> Melrose Park, PA


  #4  
Old July 16th 19, 02:15 AM posted to rec.audio.tubes
buffstereo
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Posts: 3
Default 171a

On Tuesday, July 9, 2019 at 5:23:18 AM UTC-7, Peter Wieck wrote:
> On Tuesday, July 9, 2019 at 2:05:49 AM UTC-4, Paul James wrote:
> > Does anyone here have any experience with using 171a in a linestage. Thinking of using constant current.

>
> The 71A is a low-gain DHT that is valued and prized by the Vintage Radio community. You in the Audio Community have multiple options for this purpose that do not suck resources from your cousin. Who have, too often, no viable alternatives.
>
> Peter Wieck
> Melrose Park, PA


  #5  
Old July 16th 19, 02:27 AM posted to rec.audio.tubes
buffstereo
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Posts: 3
Default 171a

On Monday, July 15, 2019 at 6:15:16 PM UTC-7, buffstereo wrote:
> On Tuesday, July 9, 2019 at 5:23:18 AM UTC-7, Peter Wieck wrote:
> > On Tuesday, July 9, 2019 at 2:05:49 AM UTC-4, Paul James wrote:
> > > Does anyone here have any experience with using 171a in a linestage. Thinking of using constant current.

> >
> > The 71A is a low-gain DHT that is valued and prized by the Vintage Radio community. You in the Audio Community have multiple options for this purpose that do not suck resources from your cousin. Who have, too often, no viable alternatives.
> >
> > Peter Wieck
> > Melrose Park, PA


Sorry for my inept response to Peter Wieck as regards 171A triodes. (Repeated attempts, 20 years since I've posted). I'm on the stereo side of the fence cousin, but if only a 171A will save your sweet radio, I'm sure I can find and give it to you for free. Only one, and nobody else, but I get the honest angst of a tube gear lover, so contact me and I'll try to help out. Good luck with your music! Robert Thompson

On Monday, July 15, 2019 at 6:15:16 PM UTC-7, buffstereo wrote:
> On Tuesday, July 9, 2019 at 5:23:18 AM UTC-7, Peter Wieck wrote:
> > On Tuesday, July 9, 2019 at 2:05:49 AM UTC-4, Paul James wrote:
> > > Does anyone here have any experience with using 171a in a linestage. Thinking of using constant current.

> >
> > The 71A is a low-gain DHT that is valued and prized by the Vintage Radio community. You in the Audio Community have multiple options for this purpose that do not suck resources from your cousin. Who have, too often, no viable alternatives.
> >
> > Peter Wieck
> > Melrose Park, PA


  #6  
Old July 16th 19, 01:48 PM posted to rec.audio.tubes
Peter Wieck[_2_]
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Posts: 99
Default 171a

Robert, thank you for the offer!

I keep enough 71As for my needs into the foreseeable future, and I keep several in reserve for other collectors as may be needed. I straddle the fence between Audio and Radio, and so I am acutely sensitive to the mis-adaptation of vintage tubes.

I am a member of the DVHRC, and we have our twice-yearly Kutztown Radio Shows in May and September. If you are nearby, please join us. There is a strong leavening of Audio, and increasing, with each show.

http://www.dvhrc.com/docs/Upcomingshowinfo.pdf

I run the repair clinic at the Club table.

Peter Wieck
Melrose Park, PA
  #7  
Old July 21st 19, 04:44 AM posted to rec.audio.tubes
Big Bad Bob
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Posts: 348
Default 171a

On 2019-07-15 18:15, buffstereo wrote:> On Tuesday, July 9, 2019 at
5:23:18 AM UTC-7, Peter Wieck wrote:
>> On Tuesday, July 9, 2019 at 2:05:49 AM UTC-4, Paul James wrote:
>>> Does anyone here have any experience with using 171a in a

linestage. Thinking of using constant current.
>>
>> The 71A is a low-gain DHT that is valued and prized by the Vintage

Radio community. You in the Audio Community have multiple options for
this purpose that do not suck resources from your cousin. Who have, too
often, no viable alternatives.
interesting

Well the antique radio crowd has often had to re-wind transformers and
do other things to restore an old radio to "original" as much as possible.

So here's a thought: what if it were possible to actually RE-BUILD one
of those old tubes? It would require all of the right stuff, vacuum
gear, glass blowing equipment, and some way to make all of the various
electrode components according to the original spec. You might even
need 'exotic metals', dangerous chemicals, nitrogen purges to get rid of
O2 and H2O vapor, and so on.

There was once a popularity of picture tube re-building "kits", ones
I've heard about online anyway, where you'd get a set of popular
electron guns to put into 'dud' tubes. I suppose they could also be
re-phosphored somehow, not sure how well THAT would work. But the
skills and equipment to do that sort of thing isn't all that available
any more, and I'm sure there are *RIDICULOUS* "environmental"
stupid-laws that get in the way of doing that sort of thing on a
commercial basis. Quite frankly, you could NEVER get zoning for that
sort of thing inside of a city. This is probably why most tubes are now
made in eastern Europe [where they even use leaded gasoline still, from
what I've heard], and in Ruswia, and in China, and other places where
they seem to NOT have a problem with polluting everything around them.

[I wouldn't want to pollute everything, just design the systems
carefully so that the hazardous material can be properly disposed of,
and NOT "ban it outright" in a knee-jerk overreaction as is the case all
too often, especially in places like Cali-Fornicate-You]

In any case, I've seen stuff online about home-made tubes. To do these
right you need the original specs and drawings so you can replicate the
parts and the distances properly. Then you'd have to be able to curve
trace them [to verify the specs match] and somehow recycle the fallouts
so you aren't tossing a lot of valuable (possibly rare, possibly
expensive) materials.

and it would be VERY labor intensive, unless there's some kind of
robotic manufacturing process that could do customized tube re-making.

So things I think would be needed that could re-use components:

a) replacement heaters
b) cathode re-coating
c) insulator disk replacement
d) socket replacement [probably have to because of the glass seals
around the pins, you'd have to re-do all of this probably]
e) 'getter material' and that silvery spot that consists of sodium or
some other oxygen scavenging metal

Other than that, if the grids aren't damaged, and the cathode needs
re-coating but is otherwise ok, then a replacement filament plus re-coat
cathode and the tube should be like new again. Well, after getting the
vacuum and getter stuff right, anyway.

[there'dd be no money in it, and it'd have to be a kind of "labor of
love" hobby by people who want to preserve antique radios and tube
electronics in general]

My $.10 worth
  #8  
Old July 22nd 19, 08:21 PM posted to rec.audio.tubes
Peter Wieck[_2_]
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Posts: 99
Default 171a

For most "popular" vintage radio tubes (Valves), there are solid-state replacements. And a small amplifying triode such as the 71A is a trivial exercise along those lines.

Put in a glass device for appearance. Put in a solid-state device for operation.

Refurbishing a globe tube - not so much.

Peter Wieck
Melrose Park, PA
  #9  
Old August 25th 19, 09:18 PM posted to rec.audio.tubes
Big Bad Bob
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Posts: 348
Default 171a

On 2019-07-22 12:21, Peter Wieck wrote:
> For most "popular" vintage radio tubes (Valves), there are solid-state replacements. And a small amplifying triode such as the 71A is a trivial exercise along those lines.
>
> Put in a glass device for appearance. Put in a solid-state device for operation.
>
> Refurbishing a globe tube - not so much.
>
> Peter Wieck
> Melrose Park, PA
>


yeah I wouldn't want to refurbish a tube amp with solid state
replacements, though. New designs, maybe. Some MOSFET devices would
work very well in that kind of application, hundreds of volts Vds etc..
JFET seems possible also but not sure if the parts would be as easily
available.

Most of the time I deal with MOSFETs for switching, like voltage control
from a microcontroller, so it's alwaysw enhancement types, not too
concerned about linearity. Depletion MOSFETS with linear operating
ranges are 'out there' but not sure how they're being used in non-RF
linear applications these days. Probably a lot available in online
parts selectors.


--
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

'your story is so touching, but it sounds just like a lie'
"Straighten up and fly right"
  #10  
Old August 26th 19, 08:42 AM posted to rec.audio.tubes
Big Bad Bob
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Posts: 348
Default 171a

On 2019-07-22 12:21, Peter Wieck wrote:
> Refurbishing a globe tube - not so much.


at some point in time, may be no other alternative...

I'd just be curious if anyone's willing to do that.
 




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