Jim Thomson> Date: Sat, 12 Oct 2013 07:04:48 -0400 (EDT)
Jim Thomson> From: Louis Parascondola <gudguyham@aol.com>
Jim Thomson> To: amps@contesting.com
Jim Thomson> Subject: [Amps] Ameritron AL-82/1200/1500 amps mis-wired!
Jim Thomson> For those of you who might have any of these amps, they
Jim Thomson> are mis wired. Seems that pretty much all of them going
Jim Thomson> back quite some time. They are not wired according to
Jim Thomson> the schematic and therefore a possible shock hazard is
Jim Thomson> possible. One might assume that when interlock switch S5
Jim Thomson> is open (cover removed) that there is ZERO high voltage
Jim Thomson> in the amp. But due to the mis wiring there is about
Jim Thomson> 400vdc which is in the power supply and on the tube
Jim Thomson> anodes. I suggest you "CAREFULLY" make the test to your
Jim Thomson> amp to see if the problem exists. Simply remove the
Jim Thomson> cover and turn the amp on and look at the HV meter. If
Jim Thomson> you get any reading other than zero, your amp is
Jim Thomson> mis-wired and you should consider wiring it properly.
Jim Thomson> The fix is simple. There is a blue/white wire coming from
Jim Thomson> the contactor relay going over to the step start relay at
Jim Thomson> junction with R3. There is a wire on S5 (on left contact
Jim Thomson> as viewed from front). These 2 wires need to be switched
Jim Thomson> to conform to the schematic. In doing so, th
Jim Thomson> e 400vdc with S5 open goes away. Although the manual
Jim Thomson> states never to plug the amp in with the lid off, I know
Jim Thomson> many of us do troubleshooting and we may wrongly assume
Jim Thomson> that no HV is present when S5 is open. If you are not
Jim Thomson> qualified to make the repair, ask someone that is to do
Jim Thomson> it for you. I believe this is a repair that should be
Jim Thomson> made to all these amps that exhibit this problem. Please
Jim Thomson> be careful in making the test or doing the repair. Lou
Jim Thomson> ## I have NOT looked at the schematic. Does the
Jim Thomson> Interlock short the B+ to the chassis..or does it open
Jim Thomson> off the 240vac to the plate xfmr....or both....or what ??
Jim Thomson> Is the problem on older amps... or newer vintage
Jim Thomson> versions?? IE: how widespread is the issue ?
Jim Thomson> Surprised somebody hasn’t fried themselves already.
Jim Thomson> Either way, the correct procedure would be.... to also
Jim Thomson> chassis ground the B+ with an alligator clip. Then
Jim Thomson> you know its at zero volts. Clip goes on 1st....and comes off
dead last.
Jim Thomson> Then if something else goes wrong...... you are
Jim Thomson> covered. If you want to be super safe, use 2-3
Jim Thomson> clips..and grnd the B+ in two different places...like
Jim Thomson> the anodes, and the B+ end of the
Jim Thomson> string of HV filter caps. Another good place is
Jim Thomson> directly between the B+ and B- of the string of filter caps.
Jim Thomson> ## Ameritron of course, should be notified. Its not
Jim Thomson> a design issue, its an assembly issue. IF you have the
Jim Thomson> SNs, they may be able to track it down to a specific employee or
Jim Thomson> group of employees. If they cant, they truly are idiots.
Jim Thomson> ## So much for any kind of testing of the finished
Jim Thomson> product. IE: step 1, check interlock, does Vdc and or
Jim Thomson> ACv drop to zero ? If not, check wiring XXX.
Jim Thomson> Damned good thing they are not building medical or
Jim Thomson> military or aircraft equipment.
Jim Thomson> Jim VE7RF
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14/10/2013 11:00
I read the original post as these were home assembled from kits, and
the original build manual / schematic showed an incorrect way to wire
the interlock? Or are they all commercially assembled units?
--
Best Regards,
Chris Wilson.
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