ORIGINAL MESSAGE: (may be snipped)
On Sat, 12 Oct 2013 07:04:48 -0400 (EDT), Louis wrote:
>
>For those of you who might have any of these amps, they are mis wired. Seems
>that pretty much all of them going back quite some time. They are not wired
>according to the schematic and therefore a possible shock hazard is possible.
>One might assume that when interlock switch S5 is open (cover removed) that
>there is ZERO high voltage in the amp. But due to the mis wiring there is
>about 400vdc which is in the power supply and on the tube anodes. I suggest
>you "CAREFULLY" make the test to your amp to see if the problem exists.
>Simply remove the cover and turn the amp on and look at the HV meter. If you
>get any reading other than zero, your amp is mis-wired and you should consider
>wiring it properly. The fix is simple. There is a blue/white wire coming from
>the contactor relay going over to the step start relay at junction with R3.
>There is a wire on S5 (on left contact as viewed from front). These 2 wires
>need to be switched to conform to the schematic. In doing so, t
h
> e 400vdc with S5 open goes away. Although the manual states never to plug
> the amp in with the lid off, I know many of us do troubleshooting and we may
> wrongly assume that no HV is present when S5 is open. If you are not
> qualified to make the repair, ask someone that is to do it for you. I
> believe this is a repair that should be made to all these amps that exhibit
> this problem. Please be careful in making the test or doing the repair. Lou
REPLY:
There was a very similar issue with the Heath SB-1000 many years ago. I
reported it to Heath but never heard back from them.
If you are an SB-1000 owner you should make the same check as above.
In fact, many of the Heath/Ameritron amps share some circuitry so it might
be wise to check yours just to be sure.
73, Bill W6WRT
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