[TenTec] Centurion HV Rectifier Board

[Michael Marx]

Hi Guys,

A while ago I posted about my Centurion “blowing up”.  While transmitting (CW) there was a bang and a little arcing resulting in no HV.  The fuses in the amp did not blow.  Apparently there is NO HV fuse.   Well the E trace on the HV board which is connected to the secondary of the transformer vaporized.  That was the HV fuse.  The transformer looks ok.  No smoke.  No blown fuses.  Secondary measures 50 or so ohms across the winding .  From either end of the winding to ground or the frame of the transformer shows infinite resistance.   

I removed each cap and measured leakage and ESR at full 450 VDC and they all passed just fine.  

I measured each diode with a Fluke 87 IV meter in the diode mode and all of the diodes looked good except for D21.  D21 measured short circuit on the board.  Off of the board, however, it measured ok.  When I measure across where D21 spans, I get only 15 ohms.  All of the resistors measure ok as they sit on the board.  So, I’m not sure what to think about this.

Here are 2 weird things I’ve observed.  One is that D21 shows on the board drawing but NOT in the schematic.  So I don’t know what that diode does.  It is not in the HV string.  

The other weird thing is that my board is that it is missing R41.  It looks as if it had been there and someone removed it.  

So, if anyone has any comments about how to proceed I’d sure appreciate it.

Also, if anyone has a part number for the Electrolytic cap I need to buy, I’d appreciate that, too.  There are a bazillion of them on Mouser’s website.  

73

Mike WB0SND

Michael Marx
sndtubes at vacuumtubes.com
636-939-9190

SND Tube Sales
105 N. Division St.
Bonne Terre, MO  63628