"James Sweet" wrote ...
"EADGBE" wrote ...
OK, I have fixed the final(?) issue with my long-suffering Nakamichi
CR-7 cassette deck.

A fusible resistor in the flourescent display circuit had blown,
causing the display to go dark.

Well, the replacement fusible resistor finally arrived from England,
and when I installed it, the flourescent display was as good as new.
It looks and works great.

BUT...........................

I am still measuring just under 7v AC going to the flourescent
display. According to the service manual, this should be only 3.25v
AC.

I took measurements at the flourescent display terminals AND at the
actual terminals of the transformer secondary, and the readings were
identical... 6.84v AC, give or take a tenth of a volt.

I checked the two .1uF buffer capacitors and they are both OK. And of
course, the fusible resistors are now both OK.

This is a really simple circuit, consisting of only the transformer,
the flourescent display, the fusible resistors, and the .1uF
capacitors, so there isn't a heck of a lot to diagnose.

MY QUESTION: Should I worry about this slightly off-spec voltage? Or
should I just chalk it up to a variance in the transformer
manufacturer and let it slide...hoping that the flourescent display
can handle just under 7v AC?


Is this a mains frequency transformer, or a high frequency inverter? If
the latter, a standard multimeter will read incorrectly, you need a true
RMS meter to measure it.

Indeed. In my response, I had just assumed that the filament
was being driven from a tap on the mains power transformer.
If it is from a high-frequency inverter, your (unspecified) meter
may not be reading properly.