In the pictures, before
and after, you see a new .1 uF 440 ac yellow cap but a .1 /630 vdc
Panasonic radio cap is fine too (Mouser). 95% of the time that is the
problem.
Test by putting +12V to the orange wire by a clip lead and –
12V to the case. Put the AC voltmeter clip to the white wire and the
other meter wire to same case ground (see test picture) This one put
out 250 AC , with 13V in. (!) It will be really bright.
However this one really
fought me and still did not work. I won’t bore you with details
but after a lot of sleuthing I determined that the power transistor
on top was degraded. It was not dead but degraded. It got hot and so
did resisters. (Clue!) So I had an old rusty junk 300 radio which
uses large size TO3 germanium PNP transistors too (some 300 radio
were smaller size). The large size is called TO—3. The NTE 104
is similar but expensive. Anyway, that fixed it. I found many
Germanium TO3 PNP on ebay , including 5 for 10$ shown . I bought
those. Others sell for $40 each so shop around.
As part of this afternoon
I tried modern silicon PNP but they do not work. Unlike a radio, the
bias in a switching application is not so critical so any TO 3 PNP
germanium ought to work. No insulating washer is needed if you have
to change since the metal case is grounded.