Re: Bias Boards

#36809

I understand. But he suggested -13 volts. So I am confused

Sent from my T-Mobile 4G LTE device

Show quoted text

------ 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 d 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.

Re: Bias Boards

#36808

开云体育

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 d 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.

Re: Bias Boards

#36807

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

Show quoted text

------ Original message------

From: 'Carl' km1h@... [ham_amplifiers]

Date: Sun, Apr 7, 2019 6:17 PM

To: ham_amplifiers@...;

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 d 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

Re: Bias Boards

#36806

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

Show quoted text

----- 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

Re: Bias Boards

#36805

开云体育

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

Re: Bias Boards

#36804

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

Show quoted text

----- 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.

Bias Boards

#36803

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

Re: C - resonant choke - C on track.

#36802

oops.. that should have read... with full bore current flowing,? choke? inductance DECREASES a tiny bit...and resonant freq? INCREASES? a bit.?

Jim? ?VE7RF

C - resonant choke - C on track.

#36801

I found a couple of identical .85 uf? oil caps... pulled from microwave ovens.?

I measured each one, and? #1? is .880 uf.? ? #2? is? .892 uf?

In series, they total? .442979684? uf .?

When placed across the? 127 lb Dahl? ?4H? choke, the? choke resonates at 119.56 hz.? ? That's? close enough for this application.? ?Choke is rated for? 3A? CCS.? ?With full bore current flowing, the? choke's inductance will rise a tiny bit.... and? resonant freq? will? increase slightly.? ?Apparently,? resonant choke Z? drops off faster on the low side of resonance? vs the higher side of resonance.?

Another option is to series a pair? of? .9uf? oil caps.? ?With .45 uf? across the choke, it resonates at 118 hz.?

Since I have? 3 x kilovac? ?SPST-NC? 25 kv? ceramic relays, rated at 65A? CCS,? ?I will? wire one of em? across the? choke terminals, then a 2nd one? in one leg of the resonating caps.? ?Plus? my adjustable spark gap across the? choke terminals.? ?Coils are 12 vdc.?

Then, I can? rapidly switch from a plane jane? C? input filter...to a? C-L-C? filter..... to a C-resonant choke - C? filter.? ?A? buddy modeled the? ?C-L-C? config? on? LT-spice.... then again with the? C-resonant choke - C?

config, also on? LT-Spice.? ?Both configs work..and both are overkill.? Ditto with just a plane C filter.?

-132 db? for? the? 120 hz ripple..with? the? C- resonant choke - C? filter? ( 3.66 mv p-p).??

-128 db? for the? ? 120 hz? ripple.. with the? ?C-choke - C? ?filter.? ?( (5.8 mv? p-p).?

PSUD-2? depicts? -131 db for the? C-L-C? ?filter...... and? ?>? -134 db? for the resonant choke.?

The resonant choke is supposed to improve ripple by as much as 40 db.... but that's for a? ?resonant choke setup, like old henry and collins amps.? Those amps are? a resonant choke - C? setup.?

On a C-resonant choke- C? ?filter, resonating the? filter is not buying us very much..another? 4db.? ? I will measure the test results..as I don't really trust the various software? ?models.? ?It's just an experiment anyway.... it's all? gross overkill.? ?I want to see if the software? compares to reality.?

Later... Jim? ?VE7RF

WD7S Triode Control Kit

#36800

Just wondering if anyone has a WD7S Triode Control Kit that they would be willing to sell.? I am 80 years old and building my last 8877 QRO amplifier and would like to incorporate it into my build.

Please respond off line to: WT8R@... with price.

Thank you in advance for your consideration.

73 de Dave Beard

Re: 3CPX800A7 testing questions

#36799

Hello jim.thom@...,

 Thanks  Jim,  very helpful, work has sidetracked me for a while but I
 will  post  back as to what i find but I don't think my Hi-Pot tester
 goes over 8kV

 


Best regards,
 Chris    2E0ILY       mailto:chris@...


jttnh>   
jttnh>      
jttnh>   
jttnh>     
jttnh>                 
jttnh> If the  tube is rated fo  3.5 kv, it should hipot    a lot
jttnh> more than   double that.   When driven   to max out, the RF 
jttnh> voltage in the  PI  / PI-L  will back feed via the plate block
jttnh> cap...and superimpose itself onto the  tube's  B+    DC 
jttnh> voltage.   Typ the  total  voltage will be a  little bit less
jttnh> than  double the  key down  loaded  B+  value. 



jttnh> Any good  3-500Z  will hi pot test to  12-16 kv.   A 
jttnh> 3CX-3000A7  will  easily  hi pot test to  20 kv.    The 
jttnh> 3x10/15/20  all hi pot test easily to 30 kv.  


jttnh> Once tube is warmed up  for  20 mins......with NO B+ applied,
jttnh> then check for shorts  etc.   That's when u can get cathode to
jttnh> heater shorts or cathode to grid  shorts.   Buddy with the 
jttnh> YC-156  amp went through 12 tubes....  just to get 3  good
jttnh> ones.   The 9 bad ones all developed   shorts..... but only 
jttnh> after the  heater was on for  5-10 mins. 


jttnh> If u dont  see any shorts  after  20 mins... ( test one tube
jttnh> at a time).... then do the hi pot test on each individual
jttnh> tube... removed from  socket, on the bench.   


jttnh> Let us know what they hi pot to.   Typ hi pot test is run up to aprx 5-10 microamps.


jttnh> Jim   VE7RF              
jttnh>

Re: 3CPX800A7 testing questions

#36798

If the? tube is rated fo? 3.5 kv, it should hipot? ? a lot more than? ?double that.? ?When driven? ?to max out, the RF? voltage in the? PI? / PI-L? will back feed via the plate block cap...and superimpose itself onto the? tube's? B+? ? DC? voltage.? ?Typ the? total? voltage will be a? little bit less than? double the? key down? loaded? B+? value.?

Any good? 3-500Z? will hi pot test to? 12-16 kv.? ?A? 3CX-3000A7? will? easily? hi pot test to? 20 kv.? ? The? 3x10/15/20? all hi pot test easily to 30 kv.??

Once tube is warmed up? for? 20 mins......with NO B+ applied, then check for shorts? etc.? ?That's when u can get cathode to heater shorts or cathode to grid? shorts.? ?Buddy with the? YC-156? amp went through 12 tubes....? just to get 3? good ones.? ?The 9 bad ones all developed? ?shorts..... but only? after the? heater was on for? 5-10 mins.?

If u dont? see any shorts? after? 20 mins... ( test one tube at a time).... then do the hi pot test on each individual tube... removed from? socket, on the bench.? ?

Let us know what they hi pot to.? ?Typ hi pot test is run up to aprx 5-10 microamps.

Jim? ?VE7RF

Dentron MLA 2500B

Doug Renwick

#36797

I have a beautiful Dentron MLA 2500B Amplifier that I purchased some years
ago but never turned it on and now will never need to use it. A choice I
have is to list the entire untested amp or list the amp (for conversion) and
8875 tubes separately. I know there is still a good market for those tubes
as I have sold spares last year. Any advice or interest? Shipping from
Canada is not inexpensive.

Doug

"The difference between stupidity and genius is that genius has its limits."
Albert Einstein

Re: 3CPX800A7 testing questions

#36796

Hello 'Selcor',

 Wednesday, March 6, 2019

 Thanks  a  lot  for  the  comprehensive  reply.  The  amp  uses  this
 transformer,  maybe  with  a  doubler  or  tripler,  it's hard to see
 without some dismantling. What HT should I test with from the Hi-Pot?

 

Best regards,
 Chris    2E0ILY       mailto:chris@...


Ssvnh>   
Ssvnh>      
Ssvnh>   
Ssvnh>     
Ssvnh>                 

Ssvnh> The 3CPX800A7 is essentially the same as the 3CX800A7.  The
Ssvnh> main difference is that the 3CPX800A7 is pulse rated and has a
Ssvnh> higher arc-over rating.  Consequently, it can handle higher
Ssvnh> plate voltage.  The pulse rated tube has an arc over rating of
Ssvnh> 7,000 volts so it can handle 3,500 volts on the plate whereas
Ssvnh> the standard tube has an arc-over rating of 5,000 volts and is
Ssvnh> limited to 2,500 Volts on the plate.

Ssvnh>  

Ssvnh> Unless the tubes have a direct short cold static testing is
Ssvnh> not going to do you too much good.  The only surefire way to
Ssvnh> test a tube is in the circuit it is designed for or in a test
Ssvnh> fixture that is designed to supply the proper operating 
Ssvnh> voltages etc.  Quite often a tube that tests good for shorts
Ssvnh> and other defects while cold will fail under test when it has
Ssvnh> reached the normal operating temperature.

Ssvnh>  

Ssvnh> Unfortunately, if the tubes have any serious defects you might
Ssvnh> run the risk of blowing the amp up.  Also, if it has been
Ssvnh> sitting for an extended period of time it would be a good idea
Ssvnh> to bring the amp up very slowly on a Variac.  The electrolytic
Ssvnh> caps used in many amps do not do well if they are not
Ssvnh> reformed on a regular basis.  There is no guarantee that the
Ssvnh> caps will do well even if brought up slowly, but you have a
Ssvnh> much better chance of things not going up in smoke.  The Variac
Ssvnh> I use has voltage and current meters so that I can monitor what
Ssvnh> is going on.  If I see an unexpected sharp rise in current I
Ssvnh> can stop before something goes boom.

Ssvnh>  

Ssvnh> 73,

Ssvnh>  

Ssvnh> Steve

Ssvnh>  

Ssvnh> From: ham_amplifiers@...
Ssvnh> [mailto:ham_amplifiers@...] 
Ssvnh> Sent: Tuesday, March 05, 2019 4:02 PM
Ssvnh> To: ham_amplifiers@...
Ssvnh> Subject: [ham_amplifiers] 3CPX800A7 testing questions

Ssvnh>  

Ssvnh>   



Ssvnh> 05/03/2019 20:55

Ssvnh> I have acquired an NMR linear amp made by AMP UK using two 3CPX800A7
Ssvnh> tubes. It's bought "as seen and untested" Apart from the RF power
Ssvnh> meter smashed and a coupling centre insulator missing on one of the
Ssvnh> two 1000pF vac variables all LOOKS well. These tubes are hard to find
Ssvnh> and expensive so I want to test them first, as best I can. I have the
Ssvnh> usual meters and a decent Hi-Pot tester, what's the safest way to
Ssvnh> ensure their functionality before powering it up? I don't have the pin
Ssvnh> configuration for them, so if anyone has them, or a link to them I
Ssvnh> need that info first :) The amp is designed for 400kHz to 1MHz, so I
Ssvnh> am toying with using it on MF at some stage. My Eimac Power Grid Tubes
Ssvnh> book doesn't give the pin configuration and surprisingly Googling
Ssvnh> hasn't found them either. Thanks.

Ssvnh> If the tubes are good I have a bargain, if not I have a good source of
Ssvnh> some nice bits.

Re: 3CPX800A7 testing questions

#36795

Hello Alek,

 Wow, that's a comprehensive list, thanks Alek, appreciated :)

 


Best regards,
 Chris    2E0ILY       mailto:chris@...


APvbch>   
APvbch>      
APvbch>   
APvbch>     
APvbch>                 
APvbch> The bible for tubes is here.
APvbch>  
APvbch>  
APvbch>  
APvbch>  3CX800A7 is listed.
APvbch>  
APvbch>  73, Alek. VK6APK
APvbch>  
APvbch>  On 6/03/2019 5:02 AM, Chris Wilson chris@... [ham_amplifiers]
APvbch>  wrote:
 >>
 >>    05/03/2019 20:55
 >>
 >> I have acquired an NMR linear amp made by AMP UK using two 3CPX800A7
 >> tubes. It's bought "as seen and untested" Apart from the RF power
 >> meter smashed and a coupling centre insulator missing on one of the
 >> two 1000pF vac variables all LOOKS well. These tubes are hard to find
 >> and expensive so I want to test them first, as best I can. I have the
 >> usual meters and a decent Hi-Pot tester, what's the safest way to
 >> ensure their functionality before powering it up? I don't have the pin
 >> configuration for them, so if anyone has them, or a link to them I
 >> need that info first :) The amp is designed for 400kHz to 1MHz, so I
 >> am toying with using it on MF at some stage. My Eimac Power Grid Tubes
 >> book doesn't give the pin configuration and surprisingly Googling
 >> hasn't found them either. Thanks.
 >>
 >> If the tubes are good I have a bargain, if not I have a good source of
 >> some nice bits.
 >>
 >> 
APvbch>  
APvbch>  -- 
APvbch>   From sunny Binningup
APvbch>  
APvbch>  Family Businesses:
APvbch>  SP Electrical. www.spelectrical.net.au
APvbch>  The Velvet Fox. 
APvbch>  Smart Design Electrical.
APvbch> 
APvbch>  Perth Interiors. 
APvbch>  
APvbch>  
APvbch>               
APvbch>

Re: 3CPX800A7 testing questions

#36794

开云体育

The 3CPX800A7 is essentially the same as the 3CX800A7.? The main difference is that the 3CPX800A7 is pulse rated and has a higher arc-over rating.? Consequently, it can handle higher plate voltage.? The pulse rated tube has an arc over rating of 7,000 volts so it can handle 3,500 volts on the plate whereas the standard tube has an arc-over rating of 5,000 volts and is limited to 2,500 Volts on the plate.

?

Unless the tubes have a direct short cold static testing is not going to do you too much good.? The only surefire way to test a tube is in the circuit it is designed for or in a test fixture that is designed to supply the proper operating? voltages etc.? Quite often a tube that tests good for shorts and other defects while cold will fail under test when it has reached the normal operating temperature.

?

Unfortunately, if the tubes have any serious defects you might run the risk of “blowing” the amp up.? Also, if it has been sitting for an extended period of time it would be a good idea to bring the amp up very slowly on a Variac. ?The electrolytic caps used in many amps do not do well if they are not “reformed” on a regular basis.? There is no guarantee that the caps will do well even if brought up slowly, but you have a much better chance of things not going up in smoke.? The Variac I use has voltage and current meters so that I can monitor what is going on.? If I see an unexpected sharp rise in current I can stop before something goes boom.

?

73,

?

Steve

?

Show quoted text

From: ham_amplifiers@... [mailto:ham_amplifiers@...]
Sent: Tuesday, March 05, 2019 4:02 PM
To: ham_amplifiers@...
Subject: [ham_amplifiers] 3CPX800A7 testing questions

?

05/03/2019 20:55

I have acquired an NMR linear amp made by AMP UK using two 3CPX800A7
tubes. It's bought "as seen and untested" Apart from the RF power
meter smashed and a coupling centre insulator missing on one of the
two 1000pF vac variables all LOOKS well. These tubes are hard to find
and expensive so I want to test them first, as best I can. I have the
usual meters and a decent Hi-Pot tester, what's the safest way to
ensure their functionality before powering it up? I don't have the pin
configuration for them, so if anyone has them, or a link to them I
need that info first :) The amp is designed for 400kHz to 1MHz, so I
am toying with using it on MF at some stage. My Eimac Power Grid Tubes
book doesn't give the pin configuration and surprisingly Googling
hasn't found them either. Thanks.

If the tubes are good I have a bargain, if not I have a good source of
some nice bits.

--
Best Regards,
Chris Wilson.
mailto: chris@...

Re: 3CPX800A7 testing questions

Bob Naylor

#36793

I don't know how that went here. Sorry guys.

Bob ?WE6C

Show quoted text

From: "Bob Naylor wotbob01@... [ham_amplifiers]"
To: "ham_amplifiers@..."
Sent: Tuesday, March 5, 2019 3:01 PM
Subject: Re: [ham_amplifiers] 3CPX800A7 testing questions

Will wanna keep in contact with you for sure. I know all about finally meeting the love of my life, like you did. Too bad for all of us it took so long. That means we all have to make the most of the years we all have left.

Take care and say hi to Deena, Bob

From: "Chris Wilson chris@... [ham_amplifiers]"
To: ham_amplifiers@...
Sent: Tuesday, March 5, 2019 1:31 PM
Subject: [ham_amplifiers] 3CPX800A7 testing questions

?

05/03/2019 20:55

I have acquired an NMR linear amp made by AMP UK using two 3CPX800A7
tubes. It's bought "as seen and untested" Apart from the RF power
meter smashed and a coupling centre insulator missing on one of the
two 1000pF vac variables all LOOKS well. These tubes are hard to find
and expensive so I want to test them first, as best I can. I have the
usual meters and a decent Hi-Pot tester, what's the safest way to
ensure their functionality before powering it up? I don't have the pin
configuration for them, so if anyone has them, or a link to them I
need that info first :) The amp is designed for 400kHz to 1MHz, so I
am toying with using it on MF at some stage. My Eimac Power Grid Tubes
book doesn't give the pin configuration and surprisingly Googling
hasn't found them either. Thanks.

If the tubes are good I have a bargain, if not I have a good source of
some nice bits.

--
Best Regards,
Chris Wilson.
mailto: chris@...

Virus-free.

Re: 3CPX800A7 testing questions

Bob Naylor

#36792

Will wanna keep in contact with you for sure. I know all about finally meeting the love of my life, like you did. Too bad for all of us it took so long. That means we all have to make the most of the years we all have left.

Take care and say hi to Deena, Bob

Show quoted text

From: "Chris Wilson chris@... [ham_amplifiers]"
To: ham_amplifiers@...
Sent: Tuesday, March 5, 2019 1:31 PM
Subject: [ham_amplifiers] 3CPX800A7 testing questions

05/03/2019 20:55

I have acquired an NMR linear amp made by AMP UK using two 3CPX800A7
tubes. It's bought "as seen and untested" Apart from the RF power
meter smashed and a coupling centre insulator missing on one of the
two 1000pF vac variables all LOOKS well. These tubes are hard to find
and expensive so I want to test them first, as best I can. I have the
usual meters and a decent Hi-Pot tester, what's the safest way to
ensure their functionality before powering it up? I don't have the pin
configuration for them, so if anyone has them, or a link to them I
need that info first :) The amp is designed for 400kHz to 1MHz, so I
am toying with using it on MF at some stage. My Eimac Power Grid Tubes
book doesn't give the pin configuration and surprisingly Googling
hasn't found them either. Thanks.

If the tubes are good I have a bargain, if not I have a good source of
some nice bits.

--
Best Regards,
Chris Wilson.
mailto: chris@...

Virus-free.

Re: 3CPX800A7 testing questions

#36791

The bible for tubes is here.

3CX800A7 is listed.

73, Alek. VK6APK

Show quoted text

On 6/03/2019 5:02 AM, Chris Wilson chris@... [ham_amplifiers] wrote:

   05/03/2019 20:55

I have acquired an NMR linear amp made by AMP UK using two 3CPX800A7
tubes. It's bought "as seen and untested" Apart from the RF power
meter smashed and a coupling centre insulator missing on one of the
two 1000pF vac variables all LOOKS well. These tubes are hard to find
and expensive so I want to test them first, as best I can. I have the
usual meters and a decent Hi-Pot tester, what's the safest way to
ensure their functionality before powering it up? I don't have the pin
configuration for them, so if anyone has them, or a link to them I
need that info first :) The amp is designed for 400kHz to 1MHz, so I
am toying with using it on MF at some stage. My Eimac Power Grid Tubes
book doesn't give the pin configuration and surprisingly Googling
hasn't found them either. Thanks.

If the tubes are good I have a bargain, if not I have a good source of
some nice bits.

-- 
From sunny Binningup



Family Businesses:
SP Electrical. www.spelectrical.net.au
The Velvet Fox. 
Smart Design Electrical. 
Perth Interiors. 

3CPX800A7 testing questions

#36790

05/03/2019 20:55

I have acquired an NMR linear amp made by AMP UK using two 3CPX800A7
tubes. It's bought "as seen and untested" Apart from the RF power
meter smashed and a coupling centre insulator missing on one of the
two 1000pF vac variables all LOOKS well. These tubes are hard to find
and expensive so I want to test them first, as best I can. I have the
usual meters and a decent Hi-Pot tester, what's the safest way to
ensure their functionality before powering it up? I don't have the pin
configuration for them, so if anyone has them, or a link to them I
need that info first :) The amp is designed for 400kHz to 1MHz, so I
am toying with using it on MF at some stage. My Eimac Power Grid Tubes
book doesn't give the pin configuration and surprisingly Googling
hasn't found them either. Thanks.

If the tubes are good I have a bargain, if not I have a good source of
some nice bits.

-- 
       Best Regards,
                   Chris Wilson.
mailto: chris@...