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Author: Ian Thompson-BellIan Thompson-Bell
Date: Jul 22, 2008 15:34
At a local ham fest I picked up 100 of 150V zeners so I thought I would
build myself a stabilised 300V HT supply - not big current, just enough
for my mic pre projects. So, I have been looking at high voltage
transistors and came across the TIP50 which are rated 400/500V. I picked
this oas it the only one whose number I vaguely recognise.
Has anyone used these for HT supplies or what else do you use?
Cheers
Ian
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4 Comments |
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Author: Dwight D. EisenhowerDwight D. Eisenhower
Date: Jul 22, 2008 14:32
>
> WWII SIGNAL CORPS LANTERN-U.S.ARMY-MX290GV-VINTAGE-$$$$ 0 Bids $24.99
> $45.00
> Free 6d 14h 56m
>
> 16 TAPES LOT 4-TRACK CARTRIDGES-SINATRA-PETER,PAUL,MARY 0 Bids $24.99
> $50.00
> Free 6d 14h 56m
>
> PHILCO MODEL 66 SUPERHETERODYNE ANTIQUE TUBE RADIO-$$$$ 0 Bids $49.98
> $250.00
> +$40.00 6d 14h 56m
>
> PHILCO VINTAGE BAKELITE TELEVISION BOOSTER BOX-COMPLETE 0 Bids $9.98
> +$10.00 6d 14h 56m
>
> ANTIQUE CUNNINGHAM WOOD RADIO w/TUBES-parts/fix/restore 1 Bid $24.99
> +$20.00 6d 14h 56m
> ...
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Author: GregSGregS
Date: Jul 21, 2008 09:56
I think I asked this question before, but never got any
good answers. I was checking a bunch of Telefunken 12AX7's.
I got different, mostly improved readings on the 539C tester by tapping
on the tubes. What do I believe ?
greg
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9 Comments |
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Author: patrick jankowiakpatrick jankowiak
Date: Jul 21, 2008 00:10
I was given a Presto 92-B and would like to find a schematic please.
Must be one on the WWW somewhere, but I have not turned it up.
Anyone know the difference between the 92-A and 92-B?
please remove the "REMOVE_THIS" in the e-mail address if replying,
thanks,
Patrick J.
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Author: Phil AllisonPhil Allison
Date: Jul 20, 2008 20:07
** Have an Ampeg SVT-2 Pro ( bass guitar head ) on the bench - it uses
six 6500s in parallel push pull ( class AB) with grid bias to generate about
300 watts. Drive signal to the 6550 grids comes from a pair of 12AU7s with
half of each wired as a direct coupled cathode follower.
The 12AU7's operating conditions are:
Plate voltage = + 395
Grid voltage = - 78
Cathode voltage = - 56
Cathode current = 3 mA
Plate dissipation = 1.35 watts.
Heater / cathode voltage during warm up = -195 volts.
QUESTIONS:
How long will a cheap, Chinese short plate 12AU7 survive ?
What happens to the 6550s when the heater cathode insulation fails during
warm up ?
( The above IS what happened with this one. )
Also - what 12AU7 is the most likely to be OK here ?
..... Phil
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5 Comments |
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Author: WBWB
Date: Jul 20, 2008 16:47
I have a severe 60 hum being produced by
by my home brew OctomberPlexi:
http://www.freewebs.com/willispage8/octoberbuildpage1.htm
I've cured some wrong components over the past weeks in the
tone/PS circuit that certainly awoken the beast.
Now, I have this intolerable 60 oscillation that I
think I have traced to the PT ( Weber 25130 ).
I back tracked the noise to the rectifier circuit:
There are diodes in series ( D1 -> D2 on one leg, and
D3- > D4 ) for the full wave rectifier, and connecting
a scope between D1 and D2 produces this weird wave sign
that appears on B+ as a sawtooth ripple:
http://www.freewebs.com/willispage8/pwrsupp02.jpg
Here is a little more detailed document on it:
http://www.freewebs.com/willispage8/octp1/18wpwrproblem.doc
I'm convinced it's the $50 PT ... simply because I replaced the diodes
and I used the alternate higher voltage taps and I get the same
result.
Thoughts ?
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Author: BretLudwigBretLudwig
Date: Jul 19, 2008 17:10
Why did they discontinue this excellent tool?
Completely irrelevant to tube audio but very relevant to why I like it:
>>" Toyota Wide Range Air:Fuel Sensor, John Thornton, Underhood Service,
January 2002
This month�s article is not going to focus on a specific driveability
problem, but rather a specific testing technique. Have you had the
opportunity to see a Toyota Wide Range Air:Fuel sensor yet? You may have
seen one and not even noticed it. Why? Because this new type of "oxygen"
sensor looks very similar to a conventional oxygen sensor. Photo 1 shows a
Wide Range Air:Fuel sensor in a 2001 Camry with a 2.2L engine.
At first glance, it looks like a standard 4-wire heated O2 sensor. Well,
it is definitely not a standard 4-wire O2 sensor. Toyota first started
using Wide Range Air:Fuel sensors with some 1997 models in California. By
1999, their use had spread to other Toyota and Lexus models.
Wide Range Air:Fuel sensors are sometimes called Linear Air:Fuel sensors.
Both Honda (in some limited Civics) and Cadillac (1999 Catera) have used
this unique type of air:fuel measuring device. But what is the benefit?
Let�s answer that question with a chart shown in Figure 1.
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Author: Sofa SlugSofa Slug
Date: Jul 16, 2008 18:43
I'm working on an old power supply that uses two 0B2 tubes. Both test
good, but one glows with an orange color, and the other blue. I have
several other 0B2s - all of those glow blue.
Is it unusual for an 0B2 to glow orange? Does that indicate a problem?
-Thanks
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