The AM Forum

Do any of you guys have any direct experience with the metal plate 813's offered by Taylor? They are selling for $37.50 vs about $50 for NOS RCA's. I want to buy some for the transmitter I'm building and it would save some $$. Have any of you guys tried them at full tilt? I'm a little concerned about the metal plates and how well they will hold up over time. My instinct says go NOS but if you have any favorable experience with them, I may give them a try.

I don't have any experience with those tubes, but fwiw, I don't recall seeing carbon plate 813s in general.

I'd expect that the Chinese tubes are, well, Chinese tubes. Pretty good, and work ok. Usually not quite as robust as NOS, and probably won't handle the same max B+, if they are like other Chinese tubes of not the big transmitting type that I've had a chance to play with... but otherwise pretty good. For example the Chinese 845s tend to be quite ok.

Fwiw, I think the Chinese tubes are only getting better over time.

               _-_-bear

I purchased one of these tubes during a trip to Beijing several years ago. It worked well in an ART-13. I t has seen limited use without a failure.
Skip

buy American

Dave,
       why buy Chinese 813's when there are still plenty of them showing up at local hamfests for a few bux a piece?? Used / surplus 813s still go pretty cheap as they
havent been discovered by the audiofools yet. I still saw a bunch of them this past summer at local Md., and Va. hamfests. They're out there if you look. Why use cheezy chineezy toobz if you dont have to.
                                                               The Slab Bacon

If you're going to invest that much in a tube to begin with, what's another lousy $12.50 to get a tube of known quality?

I have never tried a metal plate 813.  Mine have always been carbon plate.  I think that for a year or two before RCA went out of the tube business, they started making them with metal plates.  I would suspect the metal plate ones would be less robust and less able to handle momentary plate dissipation overloads.

About the same time they went to metal  plate 813's, they took the little shield from underneath the plate structure of the 807, and replaced the ceramic insulator supports with mica sheets - in other words, a 6L6 with separate plate cap and 5-pin base.  Obviously cheaper to manufacture.  I'd say if you can find real carbon plate 813's, go for it.

Don,
I read EIMAC tried graphite plates in the 3-500 and they had problems with grids because the plates held heat longer. I was surprised....still an 813 isn't an 813 without that big plate.

there is definately something to be said for the overall appearance of that bottle and it's massive carbon plate structure! Its a cool looking tube!!

                                                              the Slab Bacon
                                                         

Most old 813s have the carbon plate. The square plate 813 is sought after by the scientific audiophiles who can hear things. There are plenty of old ones to be found for cheap. T'wood be nice to know someone is still making good new ones though.

I thought the smaller plates on the 813's were made out of tantalum, which is pretty resistive to high doses of heat and chemical bombardment, (we use tantalum patches on our glass-lined vessels). Being that I cornered the market on 813's, I've never really felt a need to try nor have I got to the 'thinner plate' 813's in my rotation. I guess I'll have to dig them up.

I bought a few of them Taylor 813's a few years back just to give them a try, I installed one in a GE transmitter I was using, I was not getting enough drive for the next stage which was 833A's when I put the new taylor in I even had less then I had with the used 813 I was working with. in this case I had a problem, but for most uses I thing they would work out fine.  good luck!!!

Sounds about right. Most surplus 813s are not the square plate types though.
I tested several dozen a couple years ago and found no difference in operation. All the square plate ones I've seen were made when the US was making the world a safer place.

    Thanks for all the replies. I was just wondering if any had had positive or negative experience with the metal plate "Taylors" offered by RF Parts. These are of a Chinese manufacture.
     The RCA transmitting manual says their metal plate consists of zirconium plated zinc plates. I minored in chemistry but am no metallurgist. I have seen 811A's (triodes) with holes burned through the plates. I doubt the graphite plate 813's would do that.
     I will follow your advice and buy NOS graphite RCA's. Thanks!

Just for grins I pulled the new Chinese 813 equivalent (their nomenclature is FU13, whatever that means) out of the box and put it in my Meissner 150B . The output was exactly the same as the GE I pulled out. The Chinese tube has the metal plate with some cooling ribs on it-looks kool. As for the holey 811's I have had some real ugly ones that worked great.
Skip

I have an 833A with a bright shiny spot on the plate from a hot spot.  The adjacent glass in the envelope is sunk in almost an inch.  When I first got the tube I figured it was a dud and crammed it on a shelf with some old automotive junk in the garage.  Fortunately, it never got accidentally broken.  After I got the BC1-T going, I decide to run through my entire 833A collection to weed out the duds and to note the best ones.

That damaged 833A tested to be one of my very best.

I saw 4 square plate 813s at marlboro this past weekend. I told the buzzard selling them audio fools pay big bucks for them.....He was asking $20 as it was and passd them by