I am the owner of what I think you call a " high pot". It is made by Danish
firm Danbridge and goes fro 0 up to 30 kV. Basically it is, I think, a
variable high impedance DC voltage source with an audio amplifier and a
microammeter in series. As you turn up the voltage you can hear every ion
travelling across your test object and at the same time read the microampere
current. If you increase voltage, you get a cracking noise that just before
flash-over turns into a hissing sound. The flash-over should not harm your
test object as the generatosr inherent resistance is high.
Great for testing tubes, transformers, isolation and transmitters. However,
I believe piezoelectric effects in ceramics may disturb the measurments?
Weight is 12.5 kgs
Dimensions 16 1/2W x 10 1/4H x 11 3/4D
And is for sale or a swap deal?
This instrument must be similar to yours Rich?
73s de Hans SM5KI
>Från: measures <2@vc.net>
>Till: "Martin Ellis" <jmellis@ihug.co.nz>, "amps" <amps@contesting.com>
>Ämne: Re: [AMPS] 2 x 3-500z amplifiers
>Datum: mån 20 mar 2000 07.21
>
>
>>
>>Good morning,
>>While activity is quiet on the reflector, I would like to raise
>>a question about the TL922 amplifier:
>>
>>How can we assess the performance of individual tubes in a TL922?
>
>The most accurate way is to high-pot. the grid/fil. Normal withstanding
>potential @2uA is 8 to 9 kV. With a withstanding potential of under 5kV,
>the filament/grid may short when the tube is very hot. The second most
>accurate way is to measure the grid/fil. C with a digital C meter.
>Anything over 10pF indicates that the filament grid clearance is
>abnormal.
>
>>For example, after a major event is one tube faulty or do we need to
>>replace both tubes?
>
>Only tubes with low withstanding potential need to be replaced. 922s
>typically short one tube per ''main event''. .
>
>>Or if output is slowly going down, is one tube carrying the work load,
>>or are both tubes getting "soft".
>>
>no info on such
>
>>
>>It does not help to view the anode color, as one tube seems
>>to get more cooling air than the other.
>
>I measured the temp of the filament pins during operation. The 922
>cooling is Way better than it looks. The baffle with holes appears to be
>the key.
>
>>As the filaments are in series, you cannot pull one tube,and all
>>metering is of course for both tubes. Is it permitted to lift
>>one plate cap and operate the amp?
>
>No
>>
>cheers, Martin
>
>- Rich..., 805.386.3734, www.vcnet.com/measures.
>end
>
>
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