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Author Topic: Problems with AL-572 and RF Parts "Taylor 572B Tubes"  (Read 17317 times)
VK3BL
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« Reply #15 on: April 06, 2017, 01:15:56 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.

This is common on all current batch Chinese made 572B tubes.  It is of no consequence.  I have the same amp with these tubes with 6 months on them and no issues.

Arcing IS a problem with the current batch of Chinese tubes.  If your tubes arc over enough to blow the house breaker, check the top of the tubes near the anode cap wire.  ENSURE that the filament tension springs are not too close to the anode connection bar.  I had a tube where they were so close that after 30 seconds of warm up the tube would arc so badly it blew the house breaker.

Also RE grid resistors.  Remove them and the associated capacitor, and directly ground the grids.  This will bring your amp in line with current production.  My 2010 model has directly grounded grids.  This is to protect the transceiver in case of arcs.
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
VK3BL
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« Reply #16 on: April 06, 2017, 01:17:37 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.

I wouldn't be surprised if this is the case.  My second batch of 572Bs from china were of significantly worse quality than the first batch I got.  Either production quality has dropped, or this practice is occurring.

It is also in my opinion the likely reason the RF Parts ceramic base tubes are no longer available.

I do wonder if perhaps there has only been a single batch of tubes, with the best quality ones being sold first to boost the reputation, and the lower quality bins then released to an unsuspecting market that has restored faith...
« Last Edit: April 06, 2017, 01:21:22 AM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
W8JX
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« Reply #17 on: April 06, 2017, 02:48:45 AM »

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.

RF parts makes some of it money off tubes so it will test them better I think.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
VK3BL
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« Reply #18 on: April 06, 2017, 03:56:45 AM »

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.

RF parts makes some of it money off tubes so it will test them better I think.

Or it SHOULD test them better.

Don't confusing marketing and branding with engineering; most companies keep both departments thoroughly separated, Wink

As far as I'm concerned, tubes leaving RF Parts doors that have supposedly been high pot tested to 7.5k or whatever should never arc period.

Lets assume (and that is the right choice of word) that the RF Parts tubes ARE tested.  If so, why are they arcing? Because the tubes are inherently gassy, and over time in storage produce gas.  This is common with graphite plate tubes, especially Chinese ones.

The solution then is to burn in and high-pot tubes BEFORE they leave the factory, not when they ARRIVE.  RF Parts process is WRONG.

They do however honour their warranty.


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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
W8JX
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« Reply #19 on: April 06, 2017, 04:00:26 AM »

The problem with a high pot is how it is done. A cold tube will test better that a hot one because gas expands with heat.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
VK3BL
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« Reply #20 on: April 06, 2017, 04:04:27 AM »

The problem with a high pot is how it is done. A cold tube will test better that a hot one because gas expands with heat.

Have a think about the physics of that explanation for a bit.

However, I do agree that process is important.
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
KM1H
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« Reply #21 on: April 07, 2017, 01:22:11 PM »

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

I would trust RF parts over Ameritron...

Same manufacturer plus Ameritron tests them at RF unlike RFP.
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W8JX
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« Reply #22 on: April 07, 2017, 01:28:59 PM »

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

I would trust RF parts over Ameritron...

Same manufacturer plus Ameritron tests them at RF unlike RFP.

RF Parts has its own source for its white based tubes. A RF test does not prove much by itself. HiPot is a better test for gas and quality control.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM1H
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« Reply #23 on: April 07, 2017, 02:13:53 PM »

The hi-pot is OK for incoming inspection which any dummy can run, the RF is at the tech level which can show up problems not seen earlier.

I dont know what in-house proficiency RFP has at the true engineering level.
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VK3BL
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« Reply #24 on: April 08, 2017, 03:33:29 AM »

RF Parts has its own source for its white based tubes. A RF test does not prove much by itself. HiPot is a better test for gas and quality control.

Or at least DID.  I haven't seen them available for months.

I agree with Carl, a photo of RF Parts test lab would go along way to providing re-assurance, or would a description of their test process.

My guess?  They negotiate a rock bottom price, rely on manufacturer hi-pot, rely on the manufacturer printing their name on them, and then deal with any warranty returns as they arise.  Thats the most profitable route to take.

They MAY hi-pot in house... but as the OP found out, they sure as heck don't run them for 24 hours at RF Loads.

I personally think the current 572Bs floating around are the 'second bins' of the first production run.  That would explain why there are no more RF Parts 'audiophile edition' tubes.

I'd be buying from DXE or Ameritron who are probably still on their first delivery.  The first batch I bought directly from China have been very good tubes so far.  Still making 1400 PEP when driven with 100 watts in my AL-572.  Yes, I own a stupidly large Bird 8201 dummy load, so I am not breaking any rules MR RI.
« Last Edit: April 08, 2017, 03:38:18 AM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
KC2QYM
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« Reply #25 on: April 08, 2017, 04:12:56 AM »

I bought a set of 572Bs from DX Engineering simple because RF Parts couldn't be bothered with my questions about the quality between their current tubes and the ceramic based ones which as previously noted are out of stock. The representative expressed frustrated noises based on my simple straightforward questions...well I don't give my business to arrogant little imps. I wasn't sorry that I bought the tubes from DXE (who were very pleasant and responsive to my questions) and although their price was only a few dollars more for the set they shipped them free. Tubes are fine in my SB-200.
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VK3BL
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« Reply #26 on: April 10, 2017, 06:51:18 AM »

I bought a set of 572Bs from DX Engineering simple because RF Parts couldn't be bothered with my questions about the quality between their current tubes and the ceramic based ones which as previously noted are out of stock. The representative expressed frustrated noises based on my simple straightforward questions...well I don't give my business to arrogant little imps. I wasn't sorry that I bought the tubes from DXE (who were very pleasant and responsive to my questions) and although their price was only a few dollars more for the set they shipped them free. Tubes are fine in my SB-200.

Great to hear.  I want to chase up a second spare set, and DXE or Ameritron may be the way to go.  From the sounds of things RF Parts are suffering the same problems as my second batch of Chinese tubes (only 1 was serviceable out of 4).

For me, if I am going to order from the US they have to be perfect.  I can't be bothered with warranty return costs, and as it is US sourced tubes cost twice what Chinese ones do.  Oh, and eBay comes with PayPal warranty...
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
KM1H
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« Reply #27 on: April 11, 2017, 10:04:04 AM »

Quote
RF Parts has its own source for its white based tubes. A RF test does not prove much by itself. HiPot is a better test for gas and quality control.

A different based used to ID the tube as from RFP does not mean it is made elsewhere.
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W4FID
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« Reply #28 on: April 12, 2017, 01:54:08 AM »

Is the output of the amp going to a decent SWR on the coax? Is there RF on the coax shield? True, tube amps and pi output circuits tolerate higher SWR than the solid state final circuitry. But high SWR and RF on the coax can cause voltage peaks, stray currents, and "funny" results. One possibility is there is a batch of bad tubes and the ones you exchange still came in the same large carton for wherever and that carton has a high % of bad tubes. However, my experience with RF Parts has been good and I do believe they test before shipment. So a lot of bad tubes seems unusual. Another possibility is a problem at your end. High SWR, shorted coax that arcs over under high power (bad connector, pissed off neighbor stuck a pin in your cox , etc), an intermittent open center coax conductor (makes/breaks with mechanical movement) so you are damaging tubes about as fast as you plug them in. An antenna analyzer only puts very low RF into the coax and an ohm meter uses very low voltage so simple checks won't necessarily show a flash over that happens at higher power/voltage. A bad connection at the antenna or in a PL-259 can cause a lot of grief.
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KC3DR
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« Reply #29 on: April 14, 2017, 04:46:15 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. 
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