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Reviews Categories | Electron Tubes | Greenstone (USA), Inc., 4-400C Tubes Help

Reviews Summary for Greenstone (USA), Inc., 4-400C Tubes
Reviews: 2 Average rating: 2.0/5 MSRP: $$160.00 each
Description: Unlabeled glass electron tube, visually comparable to other brands. These tubes are manufactured at an unnamed facility in China. The tubes are offered with a pro-rated warranty.
Product is in production.
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You can write your own review of the Greenstone (USA), Inc., 4-400C Tubes.

W6MTF Rating: 2/5 Jun 10, 2013 17:55 Send this review to a friend
Chinese tubes are a mixed bag  Time owned: 0 to 3 months
This is not related to the 4-400C rather a larger QRO triode, the 3CX3000A7.

I have been involved in an issue regarding a Chinese 3CX3000A7. I helped another engineer refurbish an old Henry plasma linear. It needed a complete new input matching network, larger O/P roller coil and a double section plate choke to enable it to work well on 160M. I put a couple of weeks of my time into this effort. My friend ordered the Chinese tube and spoke of a great cost saving he made over a new Eimac tube. The tube looked just like an Eimac tube and it ran fine, when we got the amp going it ran as good or slightly better (lower grid current) than the Eimac 3CX3000A7 I am very familiar with.

The amplifier was shipped back to its owner who promptly forgot to connect the blower, it actually ran more than 45 minutes before the tube failed completely, melting the Teflon chimney and setting off a smoke alarm. The sockete was also ruined as was the filament choke!

My friend ordered another Chinese tube but when it was installed (after working on the chassis another 2 weeks) it exhibited very low O/P and a high input match. I was concerned because it also looked different than the first tube, the second Chinese tube had what appeared to be a glazed ceramic and the plating was different. Also the first tube did not have a serial number on it.

To help resolve the performance discrepancy I pulled out an old Eimac tube that came from a used Henry amplifier and it was installed in this box. It ran perfectly! The second Chinese tube was then returned to the supplier, knowing full well it was weak and unusable.

I called the supplier in an effort to learn what the failure mechanism was (you know, low emission, low filament curent or whatever). Well, for almost a week now there has been no response.
It looks like that is the supplier's form of applications support - Nada!
N4MPM Rating: 2/5 May 30, 2011 14:30 Send this review to a friend
Tubes subject to flashover  Time owned: 6 to 12 months
I recently purchased a pair of 4-400C tubes from Greenstone USA. The tubes arrived intact and undamaged. Visual inspection revealed them to be unmarked and unlabeled, manufacturer's code and serial number stamped into flange internally.

The tubes were represented as current manufacture, with a 1 year warrenty, pro-rated after that up to 2 years.

After installation, and run with cathode only for 24+ hours, Plate voltage was applied. Performance seemed normal, equal to other brands.

After approximately 48 hours total of operation over a period of several weeks, I was treated to a loud bang while the unit was idling, with high voltage biased off. The breaker was thrown, but visual inspection did not reveal anything out of the ordinary. Several weeks later, after no more than 4 hours additional operating, another loud bang.

This time I noticed the Plate current was not reading properly on my meter. On closer inspection, I found the protection diodes across the meter shorted, and luckily, the meter unharmed.

I did replace the diodes, checked all other fail safes in my amp., and installed an old set of Eimac tubes.

I checked the tubes but with low voltage no shorts showed up. I am not going to reinstall them and risk further damage to my equipment.

Everything is back to normal, but I will not be purchasing any more 4-400C tubes made in China.


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