[Amps] Fwd: Ameritron AL-82/1200/1500 amps mis-wired!

Mon Oct 14 07:48:15 EDT 2013

-----Original Message-----
From: Louis Parascondola <gudguyham at aol.com>
To: jim.thom <jim.thom at telus.net>
Sent: Mon, Oct 14, 2013 7:15 am
Subject: Re: [Amps]  Ameritron AL-82/1200/1500 amps mis-wired!

Jim, the interlock on these amps simply opens one leg of the 240v primary.  When the cover is off the switch is open and if the amp is turned on the HV transformer will not get primary volt, hence no HV.  BUT....due to the mis-wiring a path through the relay coil creates a small voltage (primary AC) that when rectified gives 400vdc with S5 (safety interlock switch) in the power supply and on the anodes.  If you look at the schematic (which is correct) you won't see why it happens but with the mis-wiring, it happens.  I emailed Ameritron the other day and got a response from MIKE.  Mike said they knew about the problem and at some point in time they started to re-wire the units.  HOWEVER...their "fix" still does not make the wiring conform to the schematic but the "fix" does stop the 400vdc. The fix is a band aid.  Because the wiring is still wrong the step start circuit does not delay an additional 100ms.  The schematic shows that the step start relay coil is to charge up through the 10 ohm step start resistor which is supposed to delay the relay closure by 100ms, add to that the 20ms of the contact closure time and you get 120ms of delay.  With the "fix" you only get the 20ms of actuate time.  If you know anything about these amps you would know that it is an ongoing problem that the step start relay contacts eventually weld shut.  I have replaced many of them in 20 years.  That whole circuit needs to be wired properly according to the schematic to satisfy both the HV leakage problem and the step start problem.  UNFORTUNATELY ALL units in the field have either both or one of these problems.  NO units in the field are wired 100% correctly.  EVERY unit out there needs to be modified to reflect the schematic 100%.  To save you the trouble of doping out the circuit,    I have already done the doping out and figured out what needs to be done.  There is also another wiring error, but I am not sure if they intentionally did a change and did not update the schematic.  The primary wiring does not conform to the schematic either.  The schematic shows that in the event either of the main 15A fuses blow the amp would completely shut down.  HOWEVER....the way the units are wired if one particular main fuse blows the filament transformer still operates and you get blower, lights, and filament voltage, but you loose HV.  This can cause you to continue to drive the tube with no HV present on the anode.  The grid current goes very high and I suppose damage to the tube can occur.  The filament transformer has a separate small 4A fuse to protect it but the line feeding it comes off the line side of the main fuse, hence if that main fuse blows the amp does not go completely dead as you may expect. The fix of course is to move the feed to the load side of the fuse as the schematic shows.  They may have intentionally made this change but it is up to you to configure your unit the way you want. Lou

-----Original Message-----
From: Jim Thomson <jim.thom at telus.net>
To: amps <amps at contesting.com>
Sent: Mon, Oct 14, 2013 5:24 am
Subject: [Amps]  Ameritron AL-82/1200/1500 amps mis-wired!

Date: Sat, 12 Oct 2013 07:04:48 -0400 (EDT)
From: Louis Parascondola <gudguyham at aol.com>
To: amps at contesting.com
Subject: [Amps] Ameritron AL-82/1200/1500 amps mis-wired!

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, th
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

## I have NOT looked at the schematic.       Does the Interlock  short the B+ to 
the chassis..or does it open off the 240vac to the plate xfmr....or both....or 
what ??  
Is the problem on older amps... or newer vintage versions??     IE: how 
widespread is the issue ?   Surprised somebody hasn’t fried themselves already. 
Either way, the correct procedure would be.... to also chassis ground the B+  
with an alligator clip.    Then you know its at zero volts.    Clip goes on 
1st....and comes off dead last.
Then if something else  goes wrong...... you are covered.    If you want to be 
super safe, use 2-3 clips..and grnd the B+  in two different places...like the 
anodes, and the B+ end of the
string of HV filter caps.   Another good place is directly between the  B+ and 
B-  of the string of filter caps. 

##  Ameritron of course, should be notified.    Its not a design issue, its an 
assembly issue.    IF you have the SNs, they may be able to track it down  to a 
specific employee or
group of employees.  If they cant, they truly are idiots. 

##  So much for  any kind of testing of the finished product.    IE:  step 1, 
check interlock, does Vdc and or ACv  drop to zero ?    If not, check wiring 
XXX.  
Damned good thing they are not building medical or military or aircraft 
equipment.  

Jim  VE7RF 

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