>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.
The transformer would still blow a fuse if it was shorted. To save
fuses, put a 300w lamp in series with the primary.
>
>Any ideas .....Richard or Tom ???
>
>thanks john
>
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>
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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