One thing that could possible cause a false reading is the exterior of the tube
to be dirty, especially where the ceramic to metal fits. I'd give it a good
cleaning and then check it.
Best,
Will
*********** REPLY SEPARATOR ***********
On 10/12/06 at 12:32 PM TexasRF@aol.com wrote:
>In a message dated 10/11/2006 11:23:30 A.M. Central Daylight Time,
>w8ji@w8ji.com writes:
>
>>I just bought a 8877 on Ebay advertised as new...I just
>>tested it on my
>> hipot and found it draws 40 microamps(Cold) at
>> 4000vdc...Comments from amps
>> guys? Guy says to return and he`ll refund my money if it`s
>> not DOA!
>> Wow,screwed Huh? Jim K7RDX..
>
>
>
>
>
>Hi All,
>
>A couple of years ago a friend gave me a never used still in the box 8877
>with a date code from the late 80's. A quick check showed internal leakage
>
>starting with only 1600vdc with the tube cold.
>
>After running the filament only with a fan blowing on the tube for cooling
>
>for about a week, the leakage was improved to about 3000vdc before seeing
>current. I plugged the tube in a 2m amplifier and it blew the plate fuse
>as soon
>as hv was switched on. I reconnected the primary of the plate transformer
>to
>120vac instead of 240vac for half plate voltage. I ran the tube at idle
>current for a couple more days like that and retested the leakage. It had
>improved
>to about 6kv so I returned the power supply to full voltage.
>
>At this point the tube blew another plate fuse that was replaced. I have
>since operated the amplifier at full rated power on many occasions with no
>
>problems at all. If I were more ambitious I would pull the tube and check
>the
>leakage again but the time never seems available.
>
>So, I would say that yes, your tube has a defect. But, it may well be
>quite
>usable with a bit of TLC in bringing it up to power.
>
>73,
>Gerald K5GW
>
>
>
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