[Amps] Problem with SB-1000 Power Supply

[Steve Katz]

John, the solution is obviously to just keep talking (transmitting), since
the problem only occurs when receiving!

Does sound like a transformer to case internal short...

-WB2WIK/6

"If everything seems under control, you're just not going fast enough." -
Mario Andretti

> -----Original Message-----
> From:	John [SMTP:hydro@naturecoast.net]
> Sent:	Wednesday, October 02, 2002 11:18 AM
> To:	amps@contesting.com
> Subject:	[Amps] Problem with SB-1000 Power Supply
> 
> Hi all
>  I have a very interesting problem with my SB-1000 Heathkit .....This is
> the
> same amp as the ameritron AL80a with a single 3-500z
> 
> Hears what happen.... I turn the amp on to use it, Talk on it for a few
> minutes, The amp blows the fuse for no reason while in receive... no pops,
> cracks, nothing ...just went dead while in standby
> 
> I pull the tube test ....still blows fuse.... Test diodes...Check out OK,
> but replace them anyway..Still blows fuse...Check caps .....Seem ok...
> just
> for test I leave them out .Still blows fuse with NO caps in amp.... Put it
> all back together, disconnect the B+ ....No dice
> 
> So I am just about stumped.... I disconnect the HV negative from chassis
> ....Power it up
> It comes on .... Now the power supply is totally isolated from the amp....
> As soon as I connected the negative HV from the power supply to chassis
> ground it blows the fuse.....
> 
> So the only thing I can come up with is the transformer must have some
> kind
> of internal short, Because there is no problem in the diode board or caps
> &
> the power supply will work as long as you do not connect the HV negative
> to
> the chassis
> 
> Any ideas .....Richard or Tom ???
> 
> thanks john
> 
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