>From: Bill Smith <ko4nrbs@yahoo.com>
>To: "S. J. Blackwell" <w5lu@hotmail.com>, craxd@engineer.com,
>amps@contesting.com
>Subject: Re: [Amps] Transformer core shorted to secondary winding??
>Date: Sun, 24 Jul 2005 06:25:02 -0700 (PDT)
>
>Unplugged diodes one at a time as suggested. Measured
>1300vdc with one unplugged and zero volts with it
>plugged back in and the other one unplugged.
>
>The bleeder resisotr is too hot to lay your finger on.
>
>73,
>Bill
Good. We are half wave rectifying. Why? We know this thing worked for about
a quarter century, so we don't need to re-engineer it.
Simple things first: We know which leg of the FWCT is not working.
1) make sure that the pins on the 866 socket are making contact.
2) Its been 40 yrs or so since I messed wid 866's and 872's (aren't they
pretty?), but is it possible that the 4 pin socket could worn and allow the
rectifier to be plugged in 180 deg wrong and make no contact at the cathode.
The old 866's would have had no filament glow, but the new fangled silicons?
This seems unlikely unless this happened when you changed a rectifier.
3) If (2) is unrewarding, flip the dude over and run down the wiring around
pins 1 and 4 of the constipated rectifier leg. You are going to find
something here sooner or later. I am not sure how the silicon rectifier
makes contact at pins 1 and 4. Presumably the rectifier does not short these
pins together as this would take out the 2.5 volt fil xfmr.
4) Noting (3) above, it is possible that the 2.5 fil secondary could be open
or not making contact some where resulting in one rectifier being out of the
ckt.
Gud luk, let me know and we will go furthur,
Sam, W5LU
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