[Central-Electronics] 6550 Finals

[Todd Bigelow - PS]

JM/CO wrote:

>Over the past several years, I have had the opportunity to "interview"
>various brands of this tube, and IMHO, the absolute, hands down, no contest,
>best 6550 is the Tung-Sol. These were  installed as original equipment in
>100-V transmitters. True, these are a bit pricey NOS now, but they are not
>hard to find. They were used in many applications, including pass tubes in
>HV power supplies.  I have NOT used the Svetlana tubes, but my experience
>with Russian tubes in general has been very favorable. Stay away from
>Chinese tubes. Probably in a few years, their quality  will be on a par with
>all the others, but they are not there yet.
>Chuck N1LNH
>  
>
I agree with Chuck - these tubes are tough to beat. As far as prices, 
well...it's like anything else. If you need them *now* or prefer only 
the convenient approach of shopping via ePay or such, then they'll cost 
you a bundle. However, if you keep your eyes open at 'fests and the 
like, you'll be surprised. I bought a pair of NOS Tung-Sol 6550s last 
fall for $30 from a tube vendor. Also got a pair of 75THs with a pair of 
Johnson ceramic and metal tube sockets thrown in for $75. Hate to think 
of the deals like this I missed while looking for deals on the 
big-ticket items like receivers or transmitters.

Even if you have to spend a chunk now, keep it in the back of your mind 
and be on the lookout for spares. Once you get used to thinking like 
this, it becomes second nature to look under tables, in boxes, or to ask 
whoever is selling. Besides, the old 6550 shoulder or 'coke bottle' 
shaped envelope has to be the coolest looking tube ever.

Speaking of Tung-Sol 6550s, has anyone ever changed the base on one of 
these tubes? I have a number of these tubes that were pulled from 
service and replaced regularly, unfortunately most have the center 
pin/key broken off. The metal base is crimped around the phenolic or 
plastic pin base, which makes it look a lot trickier than swapping the a 
solid bakelite base. I know they have adapters available to slip over 
the pins, but I'd prefer to swap out the base if it's feasible. Looks 
like the same set up as used on the 6146.

73 de Todd/'Boomer'  KA1KAQ