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Author Topic: Problems with AL-572 and RF Parts "Taylor 572B Tubes"  (Read 17296 times)
VK3BL
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« Reply #30 on: April 14, 2017, 04:50:31 AM »

As a follow up to my original post, I received another "New" 572B tube from RF Parts.  I installed in the AL-572 amplifier and did not observe any blue glow.  Powered up, the amplifier now easily produces 800 watts in CW mode.   Out of 9 "New" tubes, only 4 functioned properly.  4 of the defective tubes have a blue glow indicating a "gassey" condition and 1 tube arced over internally at the bottom plate connections.  As for the comment about a possible swr problem with the antenna system, 4 of the tubes in question were showing the blue glow when plate/filament voltage was applied with no rf input/output. Per a phone conversation with DX Engineering, Ameritron and even RF Parts, the blue glow indicates a defective tube and getting good tubes is still a problem.  Also, DX Engineering and Ameritron  hi-pot their tubes prior to selling them. The antenna system is new, has been swept with an analyzer and monitored with a Bird 43 watt meter.  The SWR never excedes 1.3 to 1 on the frequencies the amplifier is operated on. 


Poor RF Parts: Blue glow on the glass IS NOT A FAULT CONDITION.  If the tube isn't arcing over with 2.5 Kilovolts on the plate under RF drive, its not gassy.  Full of crappy impurities because Shu Guang don't wear gloves and their workshop looks like a blacksmith's shed, but not gassy.

My AL-572 makes 1300 watts in CW driven at 100 watts - whats wrong with yours?

I'm fall for slagging off RF Parts when warranted, but "blue glow on the glass" is well and truly out of their control, and does not indicate a bad tube.  My direct imports have had blue glow since day one, and over 6 months later still make full output with no arc overs.
« Last Edit: April 14, 2017, 04:56:40 AM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
W8JX
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« Reply #31 on: April 14, 2017, 06:21:08 AM »


My AL-572 makes 1300 watts in CW driven at 100 watts - whats wrong with yours?


My 30+ year old Dentron Clipperton QRO will make about 1100 watts with 55 watts of drive with original Centron tubes. I NEVER drive it with 100 watts.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KC3DR
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« Reply #32 on: April 14, 2017, 07:10:02 AM »

[Poor RF Parts: Blue glow on the glass IS NOT A FAULT CONDITION.  If the tube isn't arcing over with 2.5 Kilovolts on the plate under RF drive, its not gassy.  Full of crappy impurities because Shu Guang don't wear gloves and their workshop looks like a blacksmith's shed, but not gassy.

My AL-572 makes 1300 watts in CW driven at 100 watts - whats wrong with yours?

I'm fall for slagging off RF Parts when warranted, but "blue glow on the glass" is well and truly out of their control, and does not indicate a bad tube.  My direct imports have had blue glow since day one, and over 6 months later still make full output with no arc overs.]

If you read my posts you will notice that I merely repeated the information that was given to me about 572B tubes from 2 retailers and a manufacturer.  I tend to accept their response since they have the experience of dealing with this product.  Also, in my original post, I stated that some of the tubes arced over and tripped the main panel breaker.  This occurred with no RF input on more than one occasion.  Per the rep at RF parts, this indicated a problem with defective tubes and they should not show a blue glow.  RF Parts took care of my problem and hopefully the tubes will continue to function properly.  As for the amplifier output, it will make its rated output power if I drive it harder.  I stated it easily makes 800 watts which it does.  My thanks to everyone that has taken the time to post constructive comments about my problem.
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VK3BL
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« Reply #33 on: April 14, 2017, 07:23:39 AM »

Blue glow in the glass of tubes has been a phenomenon long before you or I used amplifiers; it is simply to do with the purity of the glass used to form the envelopes.  Shu Guang's glass (or manufacturing practices) are no where near that of the golden era of American made tubes.

There are numerous threads on this forum, as well as the greater internet, both ham pages and audio pages regarding blue glow and when it is and isn't a problem.

Whilst my language is to the point, please do not consider it dismissive or not constructive; you have personally seen just how hard it can be to obtain a quad of 4 Chinese 572B tubes that don't exhibit glow when new; I mean only to advise that you need not do so. 

This opinion is furnished from someone who:
1) Owns the exact same amplifier
2) Has extensively researched the subject of 'blue glow'
3) Has direct experience with the current 2 batches of Shu Guang 572B tubes.

The fact of the matter is you will probably find that over time they do start to exhibit some glow on the glass.  If I may be permitted to be constructive; I merely mean to re-assure you that this is not a problem.  I explain this not just for your benefit - but for everyone else who may read the thread with the same questions.

The other faults described are of course a problem; ones myself I have documented on these very forums on numerous occasions occurring with the current batch of 572B tubes coming out of Shu Guang right now.

Once again I ask what does your amplifier make?  If it isn't making around 1200 watts continuous @ 2.4kv with 100 watts drive on 40M band you have a problem somewhere; and it could be a dud tube or 2.  I advise you to test your amplifier under these conditions to ensure you have gotten what you paid for.

If you read page 2, you will find I have provided plenty of constructive advice regarding your specific problem, which was responded to by most of the regulars but not yourself.  I provided advice on how to 'eye ball' a 572B to make sure it wouldn't blow the breaker and damage the amp and exciter, and also how to modify your amplifier to better protect your exciter and bring it up to current production.

Despite this, I didn't receive the courtesy of a reply.  You will find that the forum regulars such as KM1H and others who provide advice to new amp owners such as yourself grow increasingly corse as threads wear on without the original poster responding.  On many occasions, we've provided the same advice over and over again, and sometimes it would just be nice to at least receive a reply.
« Last Edit: April 14, 2017, 07:41:20 AM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
VK3BL
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« Reply #34 on: April 14, 2017, 11:45:06 PM »


My AL-572 makes 1300 watts in CW driven at 100 watts - whats wrong with yours?


My 30+ year old Dentron Clipperton QRO will make about 1100 watts with 55 watts of drive with original Centron tubes. I NEVER drive it with 100 watts.

Agreed, I would have expected mine to require less drive as well but thats not the case; I can only attribute it to deliberate design on W8JI's behalf who believes amplifiers are best designed to produce full output at 100 watts.

Out of interest once I drove it with an exciter capable of 180 watts, and found it was linear up to about 130 watts of drive, so the AL-572 doesn't reach gain compression @ 100 watts drive.

Certainly, I have no problem reaching -50db IMD3,5,7,9 when using ANAN's pure signal, which only works properly when the amplifier is linear, so I do not consider 100 watts drive a problem with the AL-572 current production series.
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
KM1H
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« Reply #35 on: April 15, 2017, 06:53:00 AM »


My AL-572 makes 1300 watts in CW driven at 100 watts - whats wrong with yours?


My 30+ year old Dentron Clipperton QRO will make about 1100 watts with 55 watts of drive with original Centron tubes. I NEVER drive it with 100 watts.


There is a big difference between an 811A and 572B amp as far as a safe level of drive.

The  4 x 572B amps such as the Dentron Clipperton and 160-10 series, Hunter 2000B, Gonsets, etc will never be harmed with 100W as they are fully capable of 50W per tube. The nice thing about GG is that any excess drive is passed right thru to the output and excess drive, within reason, does not contribute to poor IMD. Saturated power transformers, low emission tubes, and driving any tube into compression will not make you popular on a ham band.

Ive driven my Clipperton L with 70-150W from the TS-950SD, compressor off, and monitored the progression on a HP spectrum analyzer. I wouldnt advise using it that way as the PS and bandswitch wouldnt like it for long Roll Eyes

Since the two tube SB-200 is capable and clean at 700W out with excellent tubes, it stands to reason that 1400W from 4 tubes is also OK all things considered.

Carl
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W8JX
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« Reply #36 on: April 15, 2017, 08:38:28 PM »


Agreed, I would have expected mine to require less drive as well but thats not the case; I can only attribute it to deliberate design on W8JI's behalf who believes amplifiers are best designed to produce full output at 100 watts.


I suspect if it was designed to tolerate 100 watts it is because many figure that only way to drive a amp is pedal to the metal and they do not know how to use the power control on rig...
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KF5NAJ
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« Reply #37 on: April 15, 2017, 09:35:31 PM »

I have found that RF Parts stands behind their tubes and gives the customer the benefit of the doubt.
All vendors are good if there is not a problem the best vendors can be found by how they take care problems
Most vendors try to avoid taking care of the customer once they get your money just because they have a fancy website or mailed catalogue, somebody is paying for all that, guess who??
There is a lot of things happening in a tube amp that can be a problem besides the tubes.
I would not buy tubes from anybody else but RF Parts, fair price and customer service, rare today.
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VK3BL
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« Reply #38 on: April 16, 2017, 12:54:14 AM »


Agreed, I would have expected mine to require less drive as well but thats not the case; I can only attribute it to deliberate design on W8JI's behalf who believes amplifiers are best designed to produce full output at 100 watts.


I suspect if it was designed to tolerate 100 watts it is because many figure that only way to drive a amp is pedal to the metal and they do not know how to use the power control on rig...

There are several good reasons to do design an amp for a 100 watt drive figure, without including the above:

1) Convenience of not changing output between barefoot / linear (for much of the world)
2) Cheap protection against 'oopses' when then switch is flicked without drive being changed
3) Limits 'SSB Overshoot' issues to a considerable degree / is more compatible
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
G3RZP
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« Reply #39 on: April 16, 2017, 03:30:29 AM »


Quote
I suspect if it was designed to tolerate 100 watts it is because many figure that only way to drive a amp is pedal to the metal and they do not know how to use the power control on rig...

There are rigs that don't have a power control as such and rely on ALC for power control. Personally, I think that's a poor approach and it does lead to power spikes amongst other ills, but rigs designed for operators with little knowledge of the technicalities probably don't have much option but to use ALC.
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W8JX
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« Reply #40 on: April 16, 2017, 04:23:16 AM »

1) Convenience of not changing output between barefoot / linear (for much of the world)

I run the same 55 watts barefoot that I drive amp with....  3db is not a big deal plus when you use amp you seem more gain from 55 watts than 100

2) Cheap protection against 'oopses' when then switch is flicked without drive being changed

Not really a issue unless you are using a 8877 or 3cx800 or like tube that it is easy to fry grid in.

3) Limits 'SSB Overshoot' issues to a considerable degree / is more compatible

CYA for lack of operator skill to properly use it?Huh
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W1QJ
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« Reply #41 on: April 16, 2017, 04:31:38 AM »

First it was a debate over 1db being discernible and now 3db isn't a big deal?   What next?
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VK3BL
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« Reply #42 on: April 16, 2017, 05:00:55 AM »

First it was a debate over 1db being discernible and now 3db isn't a big deal?   What next?

Laughs,

W8JX is on a mission, what can I say.

For the record, .5dB SNR makes all the difference in the world to QAM16 x 512 carrier digital circuits (aka ADSL2+, baseband to 2MHz), so I'm in the 1dB makes a difference to experienced SSB / CW ops camp.  Every dB SNR counts in JT65.
« Last Edit: April 16, 2017, 05:07:52 AM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
W1QJ
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« Reply #43 on: April 16, 2017, 05:12:48 AM »

On the subject of "blue in the tube"  if so many tubes can be bought that do not show any blue color in the tube, why should I or anyone else settle for a tube that does have blue color in it?  How would I know the difference if it is the "phenomenon" or really gas that someday might be an issue?
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W8JX
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« Reply #44 on: April 16, 2017, 06:55:02 AM »

First it was a debate over 1db being discernible and now 3db isn't a big deal?   What next?

Laughs,

W8JX is on a mission, what can I say.

For the record, .5dB SNR makes all the difference in the world to QAM16 x 512 carrier digital circuits (aka ADSL2+, baseband to 2MHz), so I'm in the 1dB makes a difference to experienced SSB / CW ops camp.  Every dB SNR counts in JT65.


For the record in a lab or on VHF/UHF where a rigs internal noise figure is the major limiting factor and with some modes (not SSB) 1db or so can make a difference but, some seem to try to equate this to HF SSB were QRN, QRM and QSB are major factors and with that 1db does nothing yet some want to believe otherwise and like comparing apples to oranges rather than apple to apples.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
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