[R-390] Tube Tester

[Bob Camp]

Hi

I certainly will not argue that a tube tester is a perfect gizmo. A 
working radio will always be a better way to check a tube than any tube 
tester made.

That said a tube tester does have it's place. If you have a dead IF 
strip on your only working radio you need to start with something. DC 
voltages are one way to go, a quick run through the tube tester to find 
a dead tube is another way to go.

Probably the most use I have ever gotten from a tube tester was on a 
piece of gear that had been run so long with the same set of tubes in 
it that they all were low gain. Not a single tube in the set made it 
above about 1/4 of the "minimum good" reading on the tester. Needless 
to say with every tube in there near dead troubleshooting the thing was 
a bit much ...

The thing that bothers me the most is that pretty much all of us spend 
a lot of money on tube testers that do so little for us ...

	Take Care!

		Bob Camp
		KB8TQ



On Oct 26, 2004, at 11:57 AM, Veenstra, Lester wrote:

> However, to play devils advocate (and CTM)  The best tube tester is the
> R-390 with a signal generator.
>    Les K1YCM/3    www.r-390.com
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net] On Behalf Of djmerz at 3-cities.com
> Sent: Tuesday, October 26, 2004 10:15 AM
> To: Bob Camp
> Cc: R-390 HF Receiver List
> Subject: Re: [R-390] Tube Tester
>
>
> Bob,  I would be interested in the circuit of what you propose.  Not
> that I would likely end up building it but it would be "educational" to
> see how simply it might be done.  There are other classes of 
> tubes/older
> stuff that it might be useful for as well,  best regards,  Dan
>> Hi
>>
>> One of the truly amazing things about the current surplus scene is
>> that a reasonable military tube tester (say a TV-7) from the 1950's
>> sells for almost as much as a reasonable military radio (say a R-390A)
>
>> from the same era. By the time you buy a reasonable set of test gear
>> you have invested as much or more than you put into the radio.
>>
>> So here's the question:
>>
>> Is there any interest in a "R-390A only" tube tester? As far as i can
>> see you could make one with a handful of parts that would test all the
>
>> tubes in the R390A except the rectifiers. It should do as good a job
>> as a TV-7 on the R390A tubes. One advantage would be that the number
>> of switches involved would be small. The ease of use factor on the
>> simple tester would be significant if you check a lot of tubes.
>>
>> Is anybody interested in a gizmo like this? If there is then it's
>> probably worth figuring out how to do it. A lot of us already have
>> tube testers so it may not be worth doing.
>>
>> This would be strictly a "here's the schematic go to it" type of
>> thing. I have no intention of trying to sell them or build them. All
>> the wiring would be point to point stuff. The parts except for the
>> tube sockets would all be Radio Shack type stuff. The tester should be
>
>> a reasonable weekend project with plenty of time taken off necessary
>> distractions like *using* radios.
>>
>> If you are interested let me know. The only thing I need to know is
>> weather you already have a voltmeter / current meter. If so what is
>> the lowest current range it will show? The gizmo can be designed for a
>
>> "plug in" meter or a built in. The design will be a little different
>> depending on which way we go.
>>
>> Parts list (more or less):
>>
>> one 9 pin tube socket
>> two 7 pin tube sockets
>> two 6 volt filament transformers
>> one push button
>> one dpdt switch
>> one 1N4007 diode
>> 3 - 6 0.01 uf caps
>> some number of resistors
>> a power cord, fuse and on/off switch.
>> Depending on the voting either a couple of pin jacks or a meter
>>
>> So any takers?
>>
>> 	Enjoy!
>>
>> 		Bob Camp
>> 		KB8TQ
>>
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