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Author Topic: Chinese tube manufacturing analysis  (Read 22449 times)
W8JI
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« Reply #45 on: September 22, 2011, 11:25:04 AM »

Now that we have so many opinions of Chinese tubes, what happened to the Russian tube manufacturing?  Before the Chinese got into the tube building business, it seems that I recall the Russians were "top dog" in this field.

Years ago the initial 572 tubes I got from Russia had a high mortality rate from gas right out of the box. When I tried to get some changes made, I was told they had not been produced for years. It was hinted they never even really came from Russia.

As for other amateur power level tubes,  I have never been about to track down a working factory.

 
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K8AXW
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« Reply #46 on: September 23, 2011, 09:34:44 AM »

I suspect the sole importer of Svetlana tubes which is now in England is kind of a 'buffer' between you and St. Petersburg, Russia where the tubes are supposed to be made.

As I understand it, the US no longer has an importer.

I would guess that the Russian work ethic is still hampering the export of a quality product.

I've read several posts here where Eimac, who I considered THE tube manufacturer had  lot of problems with their products.  This has been a shock and surprise.  I can understand the problems the Russian and Chinese have with building quality tubes but not Eimac.
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A Pessimist is Never Disappointed!
W8JI
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« Reply #47 on: September 23, 2011, 10:22:28 AM »

I suspect the sole importer of Svetlana tubes which is now in England is kind of a 'buffer' between you and St. Petersburg, Russia where the tubes are supposed to be made.

As I understand it, the US no longer has an importer.

I would guess that the Russian work ethic is still hampering the export of a quality product.

I've read several posts here where Eimac, who I considered THE tube manufacturer had  lot of problems with their products.  This has been a shock and surprise.  I can understand the problems the Russian and Chinese have with building quality tubes but not Eimac.

First, this was years ago and maybe things have changed. This occurred when the AL572 amp was being released. We started running production and more than half new tubes were bad from poor vacuum or gas.

Representing a manufacturer buying in hundreds or thousands, I always deal as closely as possible with engineering. I was initially told the factory was in Russia. I wanted a change in pumping down and testing, and hopefully a grid connection connection change inside the envelope and base. The official reply was 572B tubes were no longer being made and could not be altered.

The unofficial reply was the tubes were not even originally built in the USSR, and were only labeled that way as a pass through.

The first was an absolute, the second an opinion by someone directly interfacing with the factory.
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K6AER
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« Reply #48 on: September 23, 2011, 10:25:10 AM »

I agree with Tom on the Chinese tubes with as he pointed out the possible exception of the 8877. The Chinese 8877's are as good as the Eimac units and most of the time produced the same power out with less grid current. Typically at Alpha we would see 1500 watts out with 30 mA grid current. The Eimac's would require up to 40 mA for 1500 watts out.

When I worked at Alpha, developing the 8406 amplifier, we had problems with output performance with the 4CX1500B from China. In testing the Chinese tubes they would fall into two categories. Either the power would drop off after a minute at rated output or the tube would flash over upon excitation. We looked at the Eimac tubes and they did not perform any better and were twice the price. This would have made the 8406 project a non starter at $1100 a tube. We never had flash over problems with the Eimac tubs but power output at 50 MHz was still a problem.

Also when measuring the Chinese tube mechanicals I noticed the tubes seemed to be built from two different locations. The new tubes would have different flange thicknesses which said to me that no matter where the distributor was in the US the tubes were made at two different locations in China. One factory that RF Parts was using produced better batch of tubes. The tubes made by Penta Labs almost always had problems with flashover.

I have had no luck using Chinese 3CX800A7's. This is a case where you bite the bullet, pay $900 for the Eimac unit and thank your lucky stars if some one had them in stock.

The days of cheep tubes are long over. Nobody uses 500-1500 watt tube but hams. All the other commercial RF production technology like gold plating, diathermy, MRI's and such have gone solid state. No such thing as pulls any more.

I still prefer tubes over transistors for the IMD on tube designs is generally much better when weighed against the dollor.
« Last Edit: September 23, 2011, 10:45:15 AM by K6AER » Logged
AG6K
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« Reply #49 on: October 05, 2011, 03:34:22 PM »

Your timing with this post is interesting Tom.

I am waiting for a replacement tube for my Alpha 9500 and I have expressed my concern about the use of a Chinese tube from the moment I learned that is what this amp came with. I even asked if it wouldn't be wise to "upgrade" to an actual Eimac built tube and I was told "No! we have more issues with the US made tubes..."

To be fair, I am not sure if the tube is the cause of my particular issue but it seems as though this is an easy first guess. If it is the fault, would you buy an Eimac over the less expensive Chinese tube?

The amp is almost two years old and it has pretty light use (6 months a year 2 hours or so an evening on 80 and 160, some weekend use on 20M etc. The "issue" is a loss of output after the amp heats up. When first turned on I will get 1500 Watts out from 35 Watts input for about 5 minutes, then it just fades away..... .No faults, warnings, smoke or anything else is happening, just  a loss of grid current then plate current along with output. Wait for a minute or too and everything works again but for less time.

We will see, I am expecting the tube today. If it is in fact a tube failure my gut says that in spite of what Alpha/RF Concepts say, I'd be happier with a US made tube.

  I test vacuum tubes that are used in amateur radio amplifiers for shorts, gold-sputtering, and for gas  .  I have seen a # of Eimac 3-500Zs that were manufactured at their plant  in Salt Lake City, Utah that had defective anode cooler spotwelds.  When the welds broke the anodes would short against the grid.  I have never tested a Chinese 3-500Z that had this mfg defect. 
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W1QJ
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« Reply #50 on: October 05, 2011, 05:17:37 PM »

  I test vacuum tubes that are used in amateur radio amplifiers for shorts, gold-sputtering, and for gas  .  I have seen a # of Eimac 3-500Zs that were manufactured at their plant  in Salt Lake City, Utah that had defective anode cooler spotwelds.  When the welds broke the anodes would short against the grid.  I have never tested a Chinese 3-500Z that had this mfg defect.   
 
 
 
The tube in question is not 3-500z tubes Rich.  He is talking about a Chinese 4cx1500 vs an Eimac 4cx1500. To the OP, I have seen many NOS Eimac 4cx1500 tubes for sale for about $350.00.  That is about 4 times less than an brand new one from Eimac.  Since these ceramic external anode tubes do not go gassy while in storage, why not pick one up for that price and try it?  Get a replacement Chinese unit and sell it off to offset the NOS bargain Eimac?  That is what I would do.  On the other hand can we attribute this shift in power output to something else in the output train?
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AG6K
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« Reply #51 on: October 05, 2011, 06:19:48 PM »

  I test vacuum tubes that are used in amateur radio amplifiers for shorts, gold-sputtering, and for gas  .  I have seen a # of Eimac 3-500Zs that were manufactured at their plant  in Salt Lake City, Utah that had defective anode cooler spotwelds.  When the welds broke the anodes would short against the grid.  I have never tested a Chinese 3-500Z that had this mfg defect
.   
 
 
 
Quote
The tube in question is not 3-500z tubes Rich.

  I had no idea what Chinese tube was the subject, I was giving a thumbs up to later production Chinese tubes.

Quote
He is talking about a Chinese 4cx1500 vs an Eimac 4cx1500. To the OP, I have seen many NOS Eimac 4cx1500 tubes for sale for about $350.00.  That is about 4 times less than an brand new one from Eimac.  Since these ceramic external anode tubes do not go gassy while in storage, why not pick one up for that price and try it?  Get a replacement Chinese unit and sell it off to offset the NOS bargain Eimac?  That is what I would do.  On the other hand can we attribute this shift in power output to something else in the output train?

  Which Eimac  4cx1500, the A or the B ?
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