On 11/03/2012 4:38 PM, Winston wrote:
Sylvia Else wrote:

(...)

On another note, while replacing C38 has apparently cured the problem,
I'm totally mystified as to why. It would imply
that C38 had failed such that it intermittently behaved as if it had a
resistance of many kilo-ohms in parallel with it.
It seems an unlikely failure mode for a capacitor.

C38 could be a total red herring.

Lenny said yesterday afternoon:

"I don't know if this was a coincidence or what but I had taken the
above sets of voltages and had then decided to try to measure the E -
C voltage on AF126 I. As soon as I placed my probe on the collector I
must have detuned the circuit as the radio completely quit."

It may just be that the base of AF 126 I is shorting out against
its grounded can, causing it to saturate intermittently.
If C38 is close to AF126 I, Lenny might have 'bumped' the short
open whilst replacing C38.

--Winston

If the base were shorted to the grounded can, then the base voltage
would be at ground level, but it's not. That's the puzzle with this
fault - finding a credible intermitten failure that will put the base at
the voltage level seen.

Sylvia.