Re: {Collins} 32v3 need help FIXED



Following with interest:

OK, the choke was open. That means that one of the 807 screen grids tried to serve as the plate and got red hot? If so, I guess this would mean a toasted 807 screen?

Bob KF6BC
On Feb 21, 2010, at 2:29 PM, Dave Mayfield W9WRL wrote:

> Thanks to Brian Harris it's fixed. And thanks to Dave Harmon for your input also. Here's the dope if anyones interested.
> 
> 
> Msg sent to Brian
> 
> Brian, I'm in your debt.
> 
> As soon as I read this last msg from you I new what t was. You see I had swapped the 807's and ever replaced the one that kept getting hot, and the trouble stayed at the same socket. I should have figured it out myself, but I guess I was just not thinking. one of the 500uH inductors was open. You could see the spot on it that had blew. It was a half turn from the end, right where it connects to the axle lead. So I just unwrapped the other end and cleaned the wire and soldered the wire back to the axle lead. I only lost one turn. Put it back in and it works great!
> 
> Sure made me feel good to have it fixed and you should feel good too, Thanks!
> 
> Dave w9wrl
> 
> Brian Harris wrote:
> Understood about the family.
> 
> I have the schematic in front of me.  In the 32V3 book I have there are no capacitors from the 807 grids to ground but there is a capacitor (C207) which goes from the driver secondary center tap to ground.  This is the mostly likely failure but, if this is the case, both 807's should be glowing red (unless one is totally fried).  The bias voltage, which is adjusted by R305 and should be about -25V, is fed to the center tap of the driver transformer.  From there it goes through the transformer secondary to 500 uH inductors (L205/L206) and on to the grids of the 807's.  About the 807's:
> 
> 1.  One 807 could be totally dead and the 150 mA you are seeing is because flowing through the red 807 due to not having any bias.
> 
> 2.  Both 807's could be good and either the 500 uH inductor associated with the red 807 is open or the secondary winding of the driver transformer associated with the red 807 is open (bummer).
> Feel free to call me if you need.  I am usually up until 10:30PM Central.
> 
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