wmartin@ALMSA-1.ARPA (Will Martin -- AMXAL-RI) (12/14/85)
>Most of the ceramic metal tubes are more fragile, and much more >expensive (I think the 8875 is on the order of $250 each, and the 8877 >is around $500!). Paul Young, K1XM Anybody have any data on just what makes these tubes cost so much? The materials cost, after all, can't justify this -- they are not full of platinum components (as far as I know -- if they were, there'd be a brisk trade in worn-out ones!). I know that tubes for broadcast transmitters cost vast amounts -- when WRNO's shortwave transmitter went out a few weeks ago, they explained the length of downtime to the fact that they couldn't afford to stock spare tubes at $10,000 each (!) and that was what failed, and they had to wait for replacements. As for these ham-type transmitting tubes, what contributes to the cost? Is it just that they are so difficult to manufacture and that there are many failures and broken products for each finished good tube? Or are they sole-sourced from someone who is charging anything they want because there is no competition? (Shades of the DoD spare-parts brouhaha!) Regards, Will ARPA/MILNET: wmartin@almsa-1.ARPA USENET: seismo!brl-bmd!wmartin
dsi@unccvax.UUCP (Dataspan Inc) (12/14/85)
> >Most of the ceramic metal tubes are more fragile, and much more > >expensive (I think the 8875 is on the order of $250 each, and the 8877 > >is around $500!). Paul Young, K1XM > > Anybody have any data on just what makes these tubes cost so much? The > [WRNO] explained the length of downtime to the fact that they > couldn't afford to stock spare tubes at $10,000 each (!) and that was > what failed, and they had to wait for replacements. > > As for ham type transmitting tubes, what contributes to the cost? I can believe that WRNO's final amplifier(s) cost $10,000 or more. They are probably water cooled Eimacs which aren't really made new, but instead are remanufactured. This is the case with most broadcasting tubes in the nonexpendable class. I'm a broadcast engineer in my spare time, and have found that spares are not unreasonable: 4CX250F $67.75 4-400C (Amperex) $59.00 833A $65.00 845 $85.00 4CX5000 $375 rebuilt, $875 new from Varian/Eimac The problem that many hams face is not the cost of "real" RF tubes, but the cost of some "typical" ham tubes used at HF. Four 6JS6C/6KD6 horizontal sweep tubes can eat the best part of a $100 bill. Not everyone has the plate transformers lying around to operate a 4-400C or 4CX250, nor the air system sockets and chimneys required. As for the cost of the other ceramic-metal tubes cited, try CeCo or another broadcasting tube vendor. Stay away, though, from the CeCo house brand tubes (although the 833's I have in my BTA-1E modulator are still working) as they are usually made in countries still using a lot of 'em. I've heard horror stories about the Chinese inability to perform a proper pin or terminal-to-glass seal. The 807's (made in the USSR) I had almost took out my high voltage supply in the RCA transmitter (because the modulator grids are direct coupled and the tube was badly shorted out of the box). In two Collins 831F2 FM transmitters, the remanufactured tubes have lasted longer, according to the chief engineer of WPEG Concord, NC... much longer. However, there probably aren't a lot of hams using a 4CX5000 (or whatever, I think the type number is wrong - you know, ceramic-metal, bigger than a football). Spares aren't that hard to come by, but when you purchase them from the local place which carries Sams' Photofacts and that ilk, you are going to get royally reamed. Your best bet is a broadcast supply house for "real" RF tubes (not sweep tubes, however). I don't know where one would get 6JS6C's anymore without parting with $25. David Anthony DataSpan, Inc.
wjc@ll-vlsi (Bill Chiarchiaro) (12/14/85)
Eimac claims that its tubes are hand-made; maybe the ceramic tubes are more difficult to make and you are paying for the labor. Also, Eimac will give you an "anode credit" on even relatively small tubes that have failed in service. Bill N1CPK
k2sk@ky2d-2.UUCP (Bob) (12/22/85)
I believe that the answer to the question is simply the other side of the success of the solid state device industry. Tubes which at the end of the second world war were at their zenith are not relatively rare and not commonly made in the U.S. Most of the tubes we get now are from Taiwan and such. Special purpose tubes such as UHF transmitting tubes are made virtually by hand on small labor intensive assembly lines. Their cost reflects their nature: small volume, high cost of materials hand manufacture. Although the insides are not platinum, there are many costly materials, precision must be high, and the product subjected to temperature, voltage, current, etc. extremes which we are not used to in our solid state world. If you take to trouble to look up W2SUE an OT who was a vacuum tube engineer during the war (and developed the all metal vacuum tube ) he can tell you the details. All in all, having become a ham at the end of the golden age of tubes and having experienced three and 1/2 generations of logic I count myself lucky to have been around for the experience. I cannot believe that tubes will continue much longer for even the highest power amateur applications (I remember when a 2n35 put out a few mw and cost $35 "real" dollars!) Even the $10,000 Eimac monsters may one day become HPCMOS or some such! Another way to put it: All rare antiques are expensive! - Bob K2SK >>