[Boatanchors] Building A Heathkit Today !

[Mark Bell]

Yup, my 680 ohm resistor is black also.

I'm planning on replacing the 510 pF coupling caps with
0.0033 uF metal film caps.  I arrived at that number as
it was recommended that the 510 pF value be increased
by about 4X.  The local parts shop didn't have that value,
so I just upped it to what they had.

And while I'm in the neighborhood,  the .1 uF decoupling
caps are being increased to 10 uF,  and the input grid
resistor is being upped from 470K to 1 M Ohm.

I don't know about using a 5W resistor instead of the 1/2 W
unit call for.   If something happens that smokes the 1/2W
resistor, that something will still be going on  while the
5W resistor holds out.

73 Mark K3ZX

----- Original Message -----
From: <Barockteer@aol.com>
To: <bell@blazenet.net>
Sent: Saturday, August 17, 2002 4:22 PM
Subject: Re: [Boatanchors] Building A Heathkit Today !


> I just had a fire in the audio section of my DX-100, so I thought I'd
share with you what I found. The coupling caps had gone leaky, resulting in
plate voltage from the previous stage biasing the 12BY7A into large
conduction. Result: plate of 12BY7A glowing red, 680 ohm cathode resistor
smoking. I replaced the coupling caps with new metal film .01 (recommended
for better bottom end anyway), replaced the cathode resistor with 5W 680
ohm. Back on the air...
>
>
> 73,
> Tony
>