[Amps] 8877 hipot

[Will Matney]

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 at aol.com wrote:

>In a message dated 10/11/2006 11:23:30 A.M. Central Daylight Time,  
>w8ji at 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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