It is hard to argue with the Eimac
spec sheet and curves so I dont know
what
Clark has there.
I wouldnt expect a damaged tube to
exihibit such results but........
Is there any sign of internal gas (blue
glow) when testing and does the
anode show color with those high idle
currents?
Carl
----- Original Message -----
From: Alek Petkovic
vk6apk@...
[ham_amplifiers]
To:
ham_amplifiers@...
Sent: Monday, April 08, 2019 12:40 AM
Subject: Re: [ham_amplifiers] Bias
Boards
Yes, I can see your confusion.
I would have thought that Carl's
estimate of 13V would have been pretty
close to the mark, as the circuit I have
for a 3-1000Z running at 3kV, has
0V bias and idles at 180mA.
Your 39V and 225mA idling current seems
way out of whack but I can't dispute
what you are seeing.
For now, your suggested solution of
adding 24V into the bias line sounds ok
but as I have not had any experience
with the 3-1000Z, I'll bow to someone
who has been there and done it.
Cheers and good luck.
Alek. VK6APK
On 8/04/2019 10:41 AM, '
clark@...'
clark@...
[ham_amplifiers] wrote:
I understand. But he suggested -13
volts. So I am confused
Sent from my T-Mobile 4G LTE device
------ Original message------
From: Alek Petkovic
vk6apk@...
[ham_amplifiers]
Date: Sun, Apr 7, 2019 6:48 PM
To:
ham_amplifiers@...;
Cc:
Subject:Re: [ham_amplifiers] Bias Boards
Carl was talking 100mA ZSAC, not -100V
bias voltage.
Cheers, Alek.
VK6APK
On 8/04/2019 9:41 AM, '
clark@...'
clark@...
[ham_amplifiers] wrote:
I understand the differences in class
and imd. However. 13 volts won't cut
the tube off to 100 ma. I have the amp
here with the triode board all the
way up at 225 ma. Turn it down and its
300 ma. -100 suggests the class c
bias point. At 39, what the bias board
is maxed is 225. Would 50 or 60
volts not be required?
Sent from my T-Mobile 4G LTE device
------ Original message------
From: 'Carl'
km1h@...
[ham_amplifiers]
Date: Sun, Apr 7, 2019 6:17 PM
To: ham_amplifiers@yah oogroups.com;
Cc:
Subject:Re: [ham_amplifiers] Bias Boards
Class C bias means zero Ip in standby,
my comment was right out of the Eimac
tube manual for Class B modulators and
100 ma PER tube idle current.
Class B is class B no matter what your
using it for.and the tube curves will
show you a wide range of bias within
that Class. I do that with AM linears
such as a Clipperton L and run it deeper
into B than for SSB. Actual
measured IMD barely changes but the
wasted dissipation drops way down to the
point I can run 1000W PEP out with just
572B color on voice peaks.
Carl
----- Original Message -----
From: Clark Turner
clark@...
[ham_amplifiers]
To:
ham_amplifiers@...
Sent: Sunday, April 07, 2019 4:56 PM
Subject: Re: [ham_amplifiers] Bias
Boards
Thanks for the reply Carl. I am confused
as to your suggestion to use -13
volts. I am using -39 now and its still
225 MA at 4000 volts. The Sheet
lists -100 to be Class C bias.
C
On 4/7/2019 11:48 AM, 'Carl'
km1h@...
[ham_amplifiers] wrote:
My experience with the Alpha and a few
later EBS circuits is that the
switching transient spike goes out over
the air.
Several have commented the same about
the AL-80B circuit and they have
removed it, but I havent had one in here
recently to test.
The 3-1000Z is fine with 100 ma idle at
5000V in Class B and ~ -13V bias.
Carl
----- Original Message -----
From: Clark Turner
clark@...
[ham_amplifiers]
To:
ham_amplifiers@...
Sent: Sunday, April 07, 2019 12:54 PM
Subject: [ham_amplifiers] Bias Boards
I have a BTI LK2000(single 3-1000Z) that
I have rebuilt a few years ago.
The Power supply had previously been
changed to a traditional Choke
input from the factory doubler supply.
The transformer was 120 volt
primary and was limited.
I obtained a Hypersil transformer with
220 volt primary. Its a 1.5 amp
model. I used a replacement Diode board
with metering circuit for an
ALpha 77 I found on ebay along with a
40MFD Oil cap. TO finish it off I
used a large contactor.
The amp runs 4000 volts(low tap) on the
plate as measured and had 350MA
of idle. I used Tony's Triode bias board
and that got me down to 225MA
with the board turned up max. The amp
runs HOT and requires a second
fan on top of the cabinet to extract
heat.
I planned to alter the Bias board with a
20 to 24 volt 1 watt Zener
diode as described on the website. This
should get me 50 something
volts of bias to cut the idle current
back more. 100ma?
Has anyone used the EBS-1 bias board? It
seems that this approach cuts
the tube off with no drive and has no
bias as the drive comes up. I
wonder if this is a worth while system?
Any drawbacks?
I do plan to upgrade the blower motor
for increased air flow but cannot
find a blower with the motor on the same
side as this one. It is no
longer available. I plan to retrofit
something in the amp while I am
working on the bias.
C
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Clark Turner
480-695-2898
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>From sunny Binningup
Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.
