开云体育

Swapped the right tube out and the condition is gone.? Looks like a problem in cold start with grid short.?

C

?

That is not possible on this brand of amplifier. The filament are in series.?

C

On 4/15/2019 6:28 PM, Alek Petkovic vk6apk@... [ham_amplifiers] wrote:

?

Pull the tubes and turn on from cold. If all ok, insert one tube at a
time and retest. If it is a temporary short, as you suggest, then it
will surely show itself and you can determine which tube is dodgy.

Cheers, Alek.
VK6APK

PS: Murphy says that the action of pulling the tube and reinserting it,
will be sufficient to remove the cold short and you'll never find which
tube it was in. Ha ha.

On 16/04/2019 6:33 AM, Clark Turner clark@...
[ham_amplifiers] wrote:
> A friend has a 2k4A amp with two 3-500Z tubes(RF parts). It has an odd
> problem. When you turn the Amp on, the Grid meter pegs backwards and the
> plate current shows 200MA. If you key the mic about 10 times it all of
> the sudden goes back to 0 grid and 0 plate current as normal.
>
> I have cleaned the relay contacts and am confident they are working
>
> I have replaced the Stud mount Zener diode as I had several spares.
>
> The amp will run the rest of the night at full power. This condition
> ONLY happens when you first turn amp on cold. It will never return until
> amp is off over night and turned back on next day.
>
> Possible Grid short on tube that is clearing up after some current is on
> it? Any suggestions?
>
> C
>
>

--
From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

开云体育

That is not possible on this brand of amplifier. The filament are in series.?

C

?

Pull the tubes and turn on from cold. If all ok, insert one tube at a
time and retest. If it is a temporary short, as you suggest, then it
will surely show itself and you can determine which tube is dodgy.

Cheers, Alek.
VK6APK

PS: Murphy says that the action of pulling the tube and reinserting it,
will be sufficient to remove the cold short and you'll never find which
tube it was in. Ha ha.

On 16/04/2019 6:33 AM, Clark Turner clark@...
[ham_amplifiers] wrote:
> A friend has a 2k4A amp with two 3-500Z tubes(RF parts). It has an odd
> problem. When you turn the Amp on, the Grid meter pegs backwards and the
> plate current shows 200MA. If you key the mic about 10 times it all of
> the sudden goes back to 0 grid and 0 plate current as normal.
>
> I have cleaned the relay contacts and am confident they are working
>
> I have replaced the Stud mount Zener diode as I had several spares.
>
> The amp will run the rest of the night at full power. This condition
> ONLY happens when you first turn amp on cold. It will never return until
> amp is off over night and turned back on next day.
>
> Possible Grid short on tube that is clearing up after some current is on
> it? Any suggestions?
>
> C
>
>

--
From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

开云体育

Thank you for the reply.? Its sad because the amp will run all night once the short is cleared.? We will swap out a spare tube one at a time to find which tube.

C

?

##? Grid? current meter? pegged? backwards...while showing plate current is usually indicative of a grid to cathode short on one of the two? tubes.? ?IF? I remember correctly,? Henry wires the directly heated cathodes in SERIES,? and uses a 10 volt @ 15A? fil xfmr.... same as the? TL-922.? ?The problem with that setup of course is...... when one? tube is removed, the other tube? won't light up !??

##? To get one tube? to light up,? u require a temp short across the cathode of the 2nd tube.... which won't work, cuz then? you have the full 10 volts? across the remaining tube..which will fry it asap.?

##? whats? needed is? either a single tube test fixture ( or a single tube amp like an? AL-80B)? and a? 5 v? fil xfmr.... or a 2? tube amp like a SB-220 /? L4B...with? both tubes removed, then? insert? each tube from the Henry amp...one at a time, into the test fixture.

##? watch out with using a 5V? @? 30A? fil xmfr on just a single tube...and no fil xfmr step start circuit.? ?W7IUV? fried several? ?single? 4-400's? that way.? ? Cold resistance is just? 1/10th the hot resistance..and with a 30A? fil xmfr being used....will? ?fry the single tube's cathode.? ?This is where a small variac comes in handy when testing flaky tubes.?

##? about the only advantage of running 2 x tubes? in series is the? bifilar can be sized for? 1/2 the current...? IE:? 15A? /? 14 gauge wire..... vs? ?30A? /? 10 gauge wire.? ?Which really isn't worth it when one tube starts to go bad.

Jim? VE7RF? ?

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

开云体育

?

What bias board are you using? Mike

-----Original Message-----
From: Alek Petkovic vk6apk@... [ham_amplifiers]
To: ham_amplifiers
Sent: Sun, Apr 14, 2019 9:29 pm
Subject: Re: [ham_amplifiers] Bias Boards

?

Well done Clark and Jim.

Thanks for the follow up and good information.

73, Alek.
VK6APK

On 15/04/2019 5:06 AM, Clark Turner clark@... [ham_amplifiers] wrote:

I got the Bias board working correctly. Thanks for Jim for the support on the phone.? The instructions should be updated for the board. It suggests adding a 10K pot in series with the factory board mounted pot. This places the two pots in series with a 100ohm so there is no way to get the full adjustment range. I ended up removing the factory trim pot and running the wires to my panel mounted pot to the board directly. This got me the 9.2K total at the board.?? Prior bias was measured at -3.5 volts and reveals why I could never get below 200MA.

Now, I can vary from 300 MA down to 0MA in a smooth action. The AMP runs much cooler.

I found gain drops slightly at 100MA or below. This is fine as the amp makes 1450 watts pep, the lowest my FT101 will load.? I plan to run a two tone test to the LP700 to get some figures of IMD at various Bias settings.

The FT101 has a huge ALC over shoot. If I use the ALC it will smack 1500 watts on the first syllable and then fall to what ever I set ALC at (example), 1000 watts.? I need to look into this issue or maybe just ignore it. Nobody seems to be able to tell on the air.

I would really like to get this down to 1000 watts pep. I use this station on 75 meters nightly and sometimes we talk for an hour or two.

Notes on installing this board:

?You can run the board across the 50K resistor.? It makes no difference in bias adjustment. This way the 50K is always inline. Might be safer if the board fails?? You would just drop to cut off.

You can run the board in the center tap line so the board is always in line and the 50K is switched.? The board does have an MOV so if board fails it will be in line.

Jim, Anything you want to add?

C

On 4/9/2019 9:56 AM, Clark Turner clark@... [ham_amplifiers] wrote:

?

I have four tubes and also several 4-1000 tubes.? Two of the 3-1000Z are brand new out of the box. All make the same current and power.? I know the B plus is correct, I used my Fluke and it reads 3950 volts at full load.? My Current meter is a new meter with a typical circuit.? The Bias board is working as I can vary it up and down with the remote Pot. All the way up the board claims 39 volts and that is still 225MA. Maybe I need to run some measurements. Maybe I will just make a traditional Bias supply.? That is what I am using on my Two X 3-1000Z amp. I run it up to 7000 volts on the plates and still have range to get idle current down to 100 MA a tube.

C

On 4/8/2019 12:08 PM, 'Carl' km1h@... [ham_amplifiers] wrote:

?

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

---
This email has been checked for viruses by AVG.


--
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

--
>From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

--
>From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898
    

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898
  

-- 
>From sunny Binningup



Family Businesses:
SP Electrical. 
The Velvet Fox. 
Smart Design Electrical. 
Perth Interiors. 

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

开云体育

开云体育

I got the Bias board working correctly. Thanks for Jim for the support on the phone.? The instructions should be updated for the board. It suggests adding a 10K pot in series with the factory board mounted pot. This places the two pots in series with a 100ohm so there is no way to get the full adjustment range. I ended up removing the factory trim pot and running the wires to my panel mounted pot to the board directly. This got me the 9.2K total at the board.?? Prior bias was measured at -3.5 volts and reveals why I could never get below 200MA.

Now, I can vary from 300 MA down to 0MA in a smooth action. The AMP runs much cooler.

I found gain drops slightly at 100MA or below. This is fine as the amp makes 1450 watts pep, the lowest my FT101 will load.? I plan to run a two tone test to the LP700 to get some figures of IMD at various Bias settings.

The FT101 has a huge ALC over shoot. If I use the ALC it will smack 1500 watts on the first syllable and then fall to what ever I set ALC at (example), 1000 watts.? I need to look into this issue or maybe just ignore it. Nobody seems to be able to tell on the air.

I would really like to get this down to 1000 watts pep. I use this station on 75 meters nightly and sometimes we talk for an hour or two.

Notes on installing this board:

?You can run the board across the 50K resistor.? It makes no difference in bias adjustment. This way the 50K is always inline. Might be safer if the board fails?? You would just drop to cut off.

You can run the board in the center tap line so the board is always in line and the 50K is switched.? The board does have an MOV so if board fails it will be in line.

Jim, Anything you want to add?

C

On 4/9/2019 9:56 AM, Clark Turner clark@... [ham_amplifiers] wrote:

?

I have four tubes and also several 4-1000 tubes.? Two of the 3-1000Z are brand new out of the box. All make the same current and power.? I know the B plus is correct, I used my Fluke and it reads 3950 volts at full load.? My Current meter is a new meter with a typical circuit.? The Bias board is working as I can vary it up and down with the remote Pot. All the way up the board claims 39 volts and that is still 225MA. Maybe I need to run some measurements. Maybe I will just make a traditional Bias supply.? That is what I am using on my Two X 3-1000Z amp. I run it up to 7000 volts on the plates and still have range to get idle current down to 100 MA a tube.

C

On 4/8/2019 12:08 PM, 'Carl' km1h@... [ham_amplifiers] wrote:

?

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

---
This email has been checked for viruses by AVG.


--
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

--
>From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

--
>From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898
    

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898
  

-- 
From sunny Binningup



Family Businesses:
SP Electrical. 
The Velvet Fox. 
Smart Design Electrical. 
Perth Interiors. 

开云体育

开云体育

I got the Bias board working correctly. Thanks for Jim for the support on the phone.? The instructions should be updated for the board. It suggests adding a 10K pot in series with the factory board mounted pot. This places the two pots in series with a 100ohm so there is no way to get the full adjustment range. I ended up removing the factory trim pot and running the wires to my panel mounted pot to the board directly. This got me the 9.2K total at the board.?? Prior bias was measured at -3.5 volts and reveals why I could never get below 200MA.

Now, I can vary from 300 MA down to 0MA in a smooth action. The AMP runs much cooler.

I found gain drops slightly at 100MA or below. This is fine as the amp makes 1450 watts pep, the lowest my FT101 will load.? I plan to run a two tone test to the LP700 to get some figures of IMD at various Bias settings.

The FT101 has a huge ALC over shoot. If I use the ALC it will smack 1500 watts on the first syllable and then fall to what ever I set ALC at (example), 1000 watts.? I need to look into this issue or maybe just ignore it. Nobody seems to be able to tell on the air.

I would really like to get this down to 1000 watts pep. I use this station on 75 meters nightly and sometimes we talk for an hour or two.

Notes on installing this board:

?You can run the board across the 50K resistor.? It makes no difference in bias adjustment. This way the 50K is always inline. Might be safer if the board fails?? You would just drop to cut off.

You can run the board in the center tap line so the board is always in line and the 50K is switched.? The board does have an MOV so if board fails it will be in line.

Jim, Anything you want to add?

C

?

I have four tubes and also several 4-1000 tubes.? Two of the 3-1000Z are brand new out of the box. All make the same current and power.? I know the B plus is correct, I used my Fluke and it reads 3950 volts at full load.? My Current meter is a new meter with a typical circuit.? The Bias board is working as I can vary it up and down with the remote Pot. All the way up the board claims 39 volts and that is still 225MA. Maybe I need to run some measurements. Maybe I will just make a traditional Bias supply.? That is what I am using on my Two X 3-1000Z amp. I run it up to 7000 volts on the plates and still have range to get idle current down to 100 MA a tube.

C

On 4/8/2019 12:08 PM, 'Carl' km1h@... [ham_amplifiers] wrote:

?

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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--
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

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>From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

--
>From sunny Binningup

Family Businesses:
SP Electrical.
The Velvet Fox.
Smart Design Electrical.
Perth Interiors.

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898

开云体育

That is the Plan. Its a major pain to get to the board as the Deck has to come off the Cabinet.? Maybe later today I can take a look inside. The tube has full output power and is the same as the other amp.? The two hole amp is an interesting design where I can run the left tube, The right tube or both.?

C

?

Get inside the? single 3-1000Z? amp....and? measure the? actual? voltage? being applied.? It may well be a simple thing,? where you have it hooked? up incorrectly, and have diverted a? huge chunk of that? 39? volts? in another direction....leaving very little V left for actual? biasing purposes.? ? I suspect you have? some voltage divider action taking place some where..and quite possibly on the board itself..or a combo of? board and? external to the board.??

Since you also have a 2 x 3-1000Z amp,? you could also use the? tube from the? single? 3-1000 Amp....and stick it into the 2 hole amp.... to verify the? tube is just fine.? ( which it probably is).?

That board has? bucket loads of bias to do the job three times over.? ?

Jim? VE7RF

-- 
Please let me quote you for your parts needs!
I offer a discount on Protunes with parts order!
Clark Turner
480-695-2898