"Arfa Daily" bravely wrote to "All" (19 Jan 06 10:36:03)
--- on the heady topic of " Marshall 4140 Amp question"

AD From: "Arfa Daily"
AD Xref: core-easynews sci.electronics.repair:355768

AD In contrast, if the output stage is drawing anything like enough
AD current to damage a transformer - and, IME, these will happily drip
AD wax for at least 5 minutes without failure - then the HT fuse should
AD ideally blow, or the surge limiter / smoothing resistor smoke, glow,
AD and go open.
AD It's probably just a matter of opinion and experience, which you
AD obviously have. I'm just making sure that those who might be reading,
AD and have less experience than you and I, understand the possible
AD dangers and cosequences d:~}

AD Arfa


A typical primary uses wire about the diameter of a hair. It really
can not drip wax for long. In some cases they are damaged merely by
high voltage spikes. The insulation breaks down. This is especially
true for older transformers because if the enamel got hot over time it
tends to oxidize (turns to carbon) and the damage is cumulative.

The thing about audio transformers is that they are to an extent
responsible for the tonal character of the amplifier. So if you
replace it with something equivalent it might never sound exactly the
same. It is a matter of the stray capacitance and feedback in how it
was wound. So you understand my being more protective of an audio
transformer than of an electro.

Now we know one of the electros is bad. It is possible the voltage
stress would have uncovered the weak one right away in a shower of
sparks, just as you said. However, an esr meter might be better.

A*s*i*m*o*v

.... I remember the 6SN7...