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Author Topic: Problems with AL-572 and RF Parts "Taylor 572B Tubes"  (Read 17309 times)
KC3DR
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Posts: 10




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« on: April 05, 2017, 05:19:50 AM »

I purchased a used AL 572 amplifier, supposedly in good working order.  After hooking up the amplifier, a hi swr condition and low output presented  itself.  Could not get more than 400 watts from amp.  Under the assumption that the tubes were defective, (no markings or numbers on tubes) I ordered a new set of Taylor tubes from RF Parts.  Upon arrival the tubes were installed.  Swr problem was gone and now had grid current that was not originally present along with proper plate current.  I operated the amplifier for about 2 hours of total ssb transmit time when a tube apparently arced internally and kicked out the house panel breaker.
I re-set the breaker and the amp functioned properly for several contacts, when it again kicked the breaker.
Noticing some blue glow inside 2 of the tubes, I obtained another set of 4 tubes from RF Parts.  When the last arc occured, the grid bias transistors were damaged so they were replaced.  No other visible damage was observed.  Today I finally installed the new tubes and  1 of them had a blue glow inside.  I used a tube from the first batch and ended up with a full set without any blue hazing.  The amp tuned up perfectly into a dummy load and easily produced 800 watts in cw mode.  I then connected the antenna system and tuned the amp into it.  75ma of grid current, 600ma of plate current and 60 watts of drive produced approximately 800 watts in ssb mode.  Made two transmissions and watched one of the new tubes arc over internally at the bottom plate connections.  Did not observe any excess current draw on the 120vac feed nor any current indication when not transmitting.  Spoke to RF Parts rep and was told they have not had this many defective tubes. 
Since I cannot test the amp any further, am considering sending it to Ameritron to check for any defect that might cause the above problems.  The amp is extremely clean, looks new internally and was manufactured in 2001.  Any thoughts would be appreciated since it is over $300 to ship amp to Ameritron for service when it might not need any repair.  Don't know what the amp could do to make tubes glow blue out of the box.

Thanks,
Rick, KC3DR
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W1QJ
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Posts: 2948




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« Reply #1 on: April 05, 2017, 05:22:48 AM »

As I told you in the Ameritron forum, there is nothing that the amp can do to make the tubes shows gas.  It is all up to the tube.  If the tube is gassy, it is gassy and will be in any amp of the same HV level.
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G3RZP
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Posts: 1225




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« Reply #2 on: April 05, 2017, 06:34:20 AM »

Is the blue glow between the tube electrodes, or just on the inside of the tube envelope? If it's between the electrodes, that is a gassy (known as 'soft' in the UK) tube. A blue fluorescence on the inside of the envelope is harmless. But it sounds to me as if you have bad tubes.
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KC3DR
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Posts: 10




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« Reply #3 on: April 05, 2017, 06:50:08 AM »

The blue glow I am observing is on the the inside glass surface.  Per the rep from RF Parts, the tubes should not glow at all. He also said he doesn't understand how I could receive so many defective tubes since they hi-pot test each tube at 7kv prior to shipping.  As for the one tube that arced over at the bottom plate connections, I cannot understand how a defect in the amplifier would cause that to happen.  The glow I am seeing is readily apparent as soon as the power switch is turned on and filament/plate voltage is applied with no RF input to the amplifier.
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K6UJ
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Posts: 1358




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« Reply #4 on: April 05, 2017, 07:04:07 AM »

The rep said that the tubes should not glow at all.  I would talk to him again and ask
to send the tubes back so they can check them for being gassy before going to the trouble and expense of having the amp checked out.  It sure sounds like a bad batch of tubes.


Bob
K6UJ
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KM1H
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Posts: 5101




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« Reply #5 on: April 05, 2017, 07:04:41 AM »

Id guess they are recycling all the returned bad tubes in hopes a few pass muster this time around. It is also possible they are out of stock of the new "improved" version.  Are any date codes visible?

Chinese tubes are notorious for poor vacuum processing AND gettering which are different processes.
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W8JX
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Posts: 13268




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« Reply #6 on: April 05, 2017, 07:19:19 AM »

Id guess they are recycling all the returned bad tubes in hopes a few pass muster this time around. esses.

I agree with this. They are likely recycled returns.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W5JO
Member

Posts: 72




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« Reply #7 on: April 05, 2017, 07:40:41 AM »

Why not purchase tubes from Ameritron.  The price is the same.
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W8JX
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Posts: 13268




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« Reply #8 on: April 05, 2017, 07:53:11 AM »

Why not purchase tubes from Ameritron.  The price is the same.

I would trust RF parts over Ameritron...
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KC3DR
Member

Posts: 10




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« Reply #9 on: April 05, 2017, 07:58:58 AM »

Well, hind sight is 20/20.  I already spent $343.80 for a set of four (4) Taylor tubes from RF Parts.  I did ask where Ameritron purchase their tubes and was told that they get them from a different source that is inferior in quality to RF Parts tubes.  I'll let you be the judge of that comment.  Bottom line is I am already committed to RF Parts for better or worse.
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W8JX
Member

Posts: 13268




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« Reply #10 on: April 05, 2017, 08:05:10 AM »

Well, hind sight is 20/20.  I already spent $343.80 for a set of four (4) Taylor tubes from RF Parts.  I did ask where Ameritron purchase their tubes and was told that they get them from a different source that is inferior in quality to RF Parts tubes.  I'll let you be the judge of that comment.  Bottom line is I am already committed to RF Parts for better or worse.

RF parts does not supply Ameritron with tubes because they want more for tubes than Ameritron is willing to pay.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KD0REQ
Member

Posts: 2365




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« Reply #11 on: April 05, 2017, 08:19:49 AM »

as i understand their labelling, Taylor tubes are your average Chinese tubes, which RF parts tests under hV to insure they are not failed from the start.  their new production RF parts 572s are customs that are made in one plant to higher standards, and have been in short supply.

they have a good reputation as a company, but they are dealing with a lowball production industry on those types.  this is why NOS 572s are a holy grail.
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W8JX
Member

Posts: 13268




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« Reply #12 on: April 05, 2017, 08:39:46 AM »

as i understand their labelling, Taylor tubes are your average Chinese tubes, which RF parts tests under hV to insure they are not failed from the start.  their new production RF parts 572s are customs that are made in one plant to higher standards, and have been in short supply.

they have a good reputation as a company, but they are dealing with a lowball production industry on those types.  this is why NOS 572s are a holy grail.

Well Ameritron likely buys tubes RF Parts rejects.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W1QJ
Member

Posts: 2948




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« Reply #13 on: April 05, 2017, 02:26:32 PM »

Why not purchase tubes from Ameritron.  The price is the same.

I would trust RF parts over Ameritron...

But yet you believe they are recycling returned tubrs and you trust them over Ameritron?   That's weird.
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KH6AQ
Member

Posts: 7785




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« Reply #14 on: April 05, 2017, 04:22:44 PM »

Will RF Parts take the tubes and give you a refund or another set of tubes?

KH6AQ formerly WX7G
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